24837143 - Stormwater BMP Operation and Maintenance Agreement - Blam Jade, LP - Recorded 02/18/2021RECORDING REQUESTED BY:
CITY OF GILROY
WHEN RECORDED MAIL DOCUMENT TO:
CITY OF GILROY
CITY CLERK
7351 ROSANNA ST
GILROY, CA 95020
RECORD AT NO FEE
PER GOVERNMENT I
APR: 84T-74-002
24837143
Regina Alcomendras
Santa Clara County - Clerk -Recorder
02/18/2021 10:59 AM
Titles: 1 Pages: 106
Fees: $0.00
Taxes: 0
Total: 0.00
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STORMWATER BMP
OPERATION AND MAINTENANCE AGREEMENT
THIS STORMWATER BMP OPERATION AND MAINTENANCE AGREEMENT ("AGREEMENT") is made
and entered into this J t8ay of uevr , 2028 by and between the City of Gilroy ("CITY") and BLAM
JADE LP ("OWNER").
RECITALS:
This AGREEMENT is made and entered into with reference to the following facts:
A. The CITY is authorized and required to regulate and control the disposition of storm and surface
waters as set forth in the CITY's National Pollutant Discharge Elimination System permit.
B. The OWNER is the owner of a certain tract or parcel of land more particularly described in Exhibit
"A" attached hereto (the "PROPERTY").
C. The OWNER desires to construct certain improvements of the kind or nature described in the
Post Construction Storm Water Pollution Prevention Ordinance, Gilroy City Code Chapter 27D (the
"ORDINANCE") on the PROPERTY that may alter existing stormwater conditions on both the
PROPERTY and adjacent lands.
D. To minimize adverse impacts due to these anticipated changes in existing storm and surface
water flow conditions, the OWNER is required by the CITY to implement Best Management Practices
("BMPs") and to build and maintain, at OWNER's expense, stormwater management facilities
("FACILITIES"), more particularly described and shown in the Stormwater Runoff Management Plan
prepared by Hannah -Brunetti
and dated April2019. Plans and any amendments thereto, are on file with the Public Works Department
of the City of Gilroy, California, and are hereby incorporated by reference.
E. The CITY has reviewed and approved the Stormwater Runoff Management Plan subject to the
execution of this AGREEMENT.
NOW, THEREFORE, in consideration of the benefit received and to be received by the OWNER,
its successors and assigns, as a result of the CITY'S approval of the Stormwater Runoff Management
Plan, the OWNER, hereby covenants and agrees with the CITY as follows:
1. Covenants Running With the Land: Property Subiect to Agreement: All of the real property
described in Exhibit "A" shall be subject to this AGREEMENT. It is intended and determined that
the provisions of this AGREEMENT shall run with the land and shall be binding on all parties
having or acquiring any right, title or interest in the real property described in Exhibit "A"
("PROPERTY") or any portion thereof and shall be for the benefit of each owner of any of said
parcels or any portion of said property and shall inure to the benefit of and be binding upon each
successor in interest of the owners thereof. Each and all of the limitations, easements,
obligations, covenants, conditions, and restrictions contained herein shall be deemed to be, and
shall be construed as equitable servitudes, enforceable by any of the owners of any of the
property subject to this AGREEMENT against any other Owner, tenant or occupant of the said
property, or any portion thereof.
48488399-0806v2
MVAKHARIA104706091
2. Responsibility for Installation, Operation and Maintenance: At their sole expense, the OWNER,
its successors and assigns, shall construct, operate and perpetually maintain the FACILITIES in
strict accordance with the Stormwater Runoff Management Plan and any amendments thereto
that have been approved by the CITY or the ORDINANCE. BMP areas are shown in EXHIBIT B.
3. Facility Modifications: At their sole expense, the OWNER, its successors and assigns, shall
make such changes or modifications to the FACILITIES as may be determined as reasonably
necessary by the CITY to ensure that the FACILITIES are properly maintained and continue to
operate as originally designed and approved. OWNER agrees that it shall not modify BMPs and
shall not allow BMP maintenance activities to alter the designed function of the FACILITIES from
its original design unless approved by the city prior to the commencement of the proposed
modification or maintenance activity.
4. Facility Inspections by the CITY: At reasonable times and in a reasonable manner as provided in
the ORDINANCE, the CITY, its agents, employees and contractors, shall have the right of
ingress and egress to the FACILITIES and the right to inspect the FACILITIES in order to ensure
that the FACILITIES are being properly maintained, are continuing to perform in an adequate
manner and are in compliance with the ORDINANCE, the Stormwater Runoff Management Plan
and any amendments thereto approved by the City.
5. Failure to Perform Required Facility Repairs or Modifications: If the OWNER fails to implement
the BMPs, maintain the facilities or correct any defects in the FACILITIES in accordance with the
approved design standards and/or the Stormwater Runoff Management Plan and in accordance
with the law and applicable regulations of the ORDINANCE, the authorized enforcement officer,
described in Gilroy City Code 27D.2, can give a 30 day written notice to correct the violation. If
the OWNER fails to correct the violations within the 30 days as specified in the notice of violation,
the CITY shall have the right to enter the PROPERTY to abate the nuisance and then recover
costs from OWNER pursuant to Gilroy City Code 27D.17.
In the event that maintenance or repair is neglected, or the FACILITIES become an immediate
danger to public health or safety, the City shall have the authority to perform maintenance and/or
repair work with 24 hours written notice. Whenever the City completes remedial work or
maintenance, the City will collect reimbursement for the costs of the work from the OWNER,
pursuant to Gilroy City Code 27D.18. The City is under no obligation to maintain or repair the
BMP, and this Agreement may not be construed to impose any such obligation on the City.
Additionally, conditions from failure to implement the BMPs or to maintain or repair the
FACILITIES shall be deemed a public nuisance subject to all procedures, abatement of such
conditions and remedies as provided in Chapter 27D of the Gilroy City Code. In addition, the
CITY may pursue such other remedies as provided by law, including, but not limited to, such civil
and criminal remedies set forth in the ORDINANCE.
6. Indemnity: The OWNER, its successors and assigns, shall defend, indemnify, and hold the CITY
harmless of and from any and all claims, liabilities, actions, causes of action, and damages for
personal injury and property damage, including without limitation reasonable attorneys' fees or
costs and court costs, arising out of or related to the OWNER'S, its successors' and/or assigns'
construction, operation or maintenance of the BMPs FACILITIES except claims, liabilities,
actions, causes of action, and damages that arise out of the CITY's sole negligence or willful
misconduct or the sole negligence or willful misconduct of any of the CITY'S employees, agents,
representatives, contractors, vendors, or consultants.
7. Obligations and Responsibilities of OWNER: Initially, the OWNER is solely responsible for the
performance of the obligations required hereunder and, to the extent permitted under applicable
law, the payment of any and all fees, fines, and penalties associated with such performance or
failure to perform under this AGREEMENT. Notwithstanding any provisions of this AGREEMENT
to the contrary, upon the recordation of a deed or other instrument of sale, transfer or other
conveyance of fee simple title to the Property or any portion thereof (a "Transfer") to a third party
(the "Transferee"), the OWNER shall be released of all of its obligations and responsibilities under
this AGREEMENT accruing after the date of such Transfer to the extent such obligations and
responsibilities are applicable to that portion of the PROPERTY included in such Transfer, but
such release shall be expressly conditioned upon the Transferee assuming such obligations and
responsibilities by recorded written agreement for the benefit of the CITY. Such written
4848-8399-0806v2
WAKHARIM04706091
agreement may be included in the Transfer deed or instrument, provided that the Transferee joins
in the execution of such deed or instrument. A certified copy of such deed, instrument or
agreement shall be provided to the CITY. The provisions of the preceding three sentences shall
be applicable to the original COVENANTOR and any successor Transferee who has assumed
the obligations and responsibilities of the COVENANTOR under this AGREEMENT as provided
above.
Pursuant to Gilroy City Code Section 27D.10, owners with structural BMPs on their property shall
complete two annual inspections per year that meet the following parameters:
(a) The property owner(s) shall be responsible for having all storm water management facilities
inspected for condition and function by a certified qualified storm water practitioner (QSP).
(b) Storm water facility inspections shall be done at least twice per year, once in fall, in
preparation for the wet season, and once in winter. Written records shall be kept of all
inspections.
Pursuant to City Code Section 27D.11 the property owner shall provide the City with their records
of inspections, maintenance and repair.
Inspection results and follow-up shall be provided to the City in report format using the City's BMP
Inspection Report template. Inspections shall include all applicable field observations required for
the specific BMP type as described in the Best Management Practices Rapid Assessment
Methodology (BMP RAM) Field Protocols document.
8. Property Transfer: Nothing herein shall be construed to prohibit a transfer by the OWNER to
subsequent owners and assigns.
9. Attorneys' Fees: In the event that any party institutes legal action against the other to interpret or
enforce this AGREEMENT, or to obtain damages for any alleged breach hereof, the prevailing
party in such action shall be entitled to reasonable attorneys' fees in addition to all other
recoverable costs, expenses and damages.
10. Further Documents: The parties covenant and agree that they shall execute such further
documents and instructions as shall be necessary to fully effectuate the terms and provisions of
this AGREEMENT.
11. Entire Agreement: This AGREEMENT constitutes the entire agreement of the parties with
respect to the subject matter contained herein and supersedes all prior agreements, whether
written or oral. There are no representations, agreements, arrangements, or undertakings, oral or
written that are not fully expresses herein.
12. Severability: In the event any part or provision of this AGREEMENT shall be determined to be
invalid or unenforceable under the laws of the State of California, the remaining portions of this
AGREEMENT that can be separated for the invalid, unenforceable provisions shall, nevertheless,
continue in full force and effect.
13. No Waiver: The waiver of any covenant contained herein shall not be deemed to be a continuing
waiver of the same or any other covenant contained herein.
14. Amendment: This AGREEMENT may be amended in whole or in part only by mutual written
agreement. Any such amendment shall be recorded in Santa Clara County, California. In the
even any conflict arises between the provisions of any such amendment and any of the
provisions of any earlier document or documents, the most recently duly executed and recorded
amendment shall be controlling.
15. Termination: In the event that the CITY shall determine at its sole discretion at any future time
that the FACILITIES are no longer required, then at the written request of the OWNER, its
successors and/or assigns, the city shall execute a release of this AGREEMENT which the
OWNER, it successors and/or assigns, shall record in the Clerk's Office, at its/their expense.
4848-8399-0806v2
MVAKHARIA104705091
16. Successors and Assigns: The covenants of the OWNER set forth in numbered Sections 1
through 15 above shall run with the land, and the burdens thereof shall be binding upon each and
every part of the property and upon the OWNER, its successors and assigns in ownership (or any
interest therein), for the benefit of Stormwater BMP Facility and each and every part thereof and
said covenants shall inure to the benefit of and be enforceable by the City, its successors and
assigns in ownership of each and every part of the Street and storm drains.
Executed the day and year first above written.
'(OWNER)
By: BLAM-JADE,' LP, A CaliforniaLimited Partnership'
Name: - Don Groppetti }�
Title: Managing General Partner
Address: PO -. Box '1431'
Visalia, CA 93291
Phone: (559) 734-3333
Email: don Cc=6mettiauto.com
(Notary acknowledgment to be attached)
4848-8399-0806v2
MVAKHARIA104706091
ACKNOWLEDGMENT
A notary public or other officer completing this
certificate verifies only the identity of the individual
who signed the document to which this certificate is
attached, and not the truthfulness, accuracy, or
-validity of that document.
State of California
County of )pA4--rc C
On Do rA"e-r I1 2b2D before me, spoorthy Joy Walters, Notary Public
(insert name and title of the officer)
personally appeared
who proved to me on the basis of satisfactovidence t ry ebe the person(&) whose name(s) is/are-
subscribed to the within instrument and acknowledged to me that he/she/they executed the same in
his/her/their authorized capacity(ies), and that by his/her#heiFsignature(s) on the instrument the
person(s), or the entity upon behalf of which the person(%) acted, executed the instrument.
I certify under PENALTY OF PERJURY under the laws of the State of California that the foregoing
paragraph is true and correct.
WITNESS my hand and official seal.
Signature
(Seal)
SPOORTHY JOY WALTERS
Comm.a2286781
Notary Public -California 19
Santa Clara County
Comm. Ex free A r 28, 2023
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CALIFORNIA ALL-PURPOSE ACKNOWLEDGMENT CIVIL ..
A notary public or other officer completing this certificate verifies only the identity of the individual who signed the
document to which this certificate is attached, and not the truthfulness, accuracy, or validity of that document.
State of California
County of St2ntA CIA174
On becem6er /it �_1020 beforeme, SAnjr0. /jaVai M0'6ru Pkl,(L
Date Here Insert Name and title of thetifficer
personally appeared
Signer(s)
who proved to me on the basis of satisfactory evidence to be the persong whose nameK is/ard
subscribed to the within instrument and acknowledged to me that helsWltho executed the same in
his/per/th0ir authorized capacity(iet), and that by his/hdr/tWr signatureW on the instrument the person*,
or the entity upon behalf of which the person.W acted, executed the instrument.
SANOM E. NAVA
_ Notary Public - California
Santa Clara County
Commission N 2262752
My Comm. Expires Nov 11. 2022
I certify under PENALTY OF PERJURY under the laws
of the State of California that the foregoing paragraph
is true and correct.
WITNESS my hand and official seal.
Signature �- • r ov"'
Signature of Notary Public
Place Notary Seal Above
OPTIONAL
Though this section is optional, completing this information can deter alteration of the document or
fraudulent reattachment of this form to an unintended document.
Description of Attached Document Ma; nfeilane . i4 reeMen+
Title or Type of Document: Sformij4+er him (liatrAhen' WDocument Date. he 8mher 17, 2020
Number of Pages: Signer(s) Other Than Named Above:
Capacity(ies) Claimed by Signer(s)
Signer's Name:
❑ Corporate Officer — Title(s):
❑ Partner — ❑ Limited ❑ General
❑ Individual ❑ Attorney in Fact
❑ Trustee ❑ Guardian or Conservator
❑ Other:
Signer Is Representing:
Signer's Name:
❑ Corporate Officer — Title(s):
❑ Partner — ❑ Limited ❑ General
❑ Individual ❑ Attorney in Fact
❑ Trustee ❑ Guardian or Conservator
❑ Other:
Signer Is Representing:
02014 National Notary Association • www.NationalNotary.org • 1-800-US NOTARY (1-800-876-6827) Item #5907
EXHIBIT B - BMP Facilities & Responsibilities Map
Reference the attached Stormwater Control Plan, Dated February 2019 and Revised April 2019 for
complete information.
4848-8399-0806V2
MVAKHARIAX04706091
Stormwater Control Plan
for
Gilroy Nissan
February 2019
Revised April 2019
Developer:
Blam-Jade LP
PO Box 1431
Visalia, CA 93279
Prepared by:
Hanna - Brunetti
7651 Eigleber y St
Gilroy, CA 95020
408 842-2173
Table of Contents
I.
Project Data.................................................................................................................. 1
II. Setting 1
II.A. Project Location and Description.......................................................................................................... 1
II.B. Existing Site Features and Conditions ..............
H.C. Opportunities and Constraints for Stormwater Control..................................................................... 4
III.
Low Impact Development Design Strategies................................................................. 5
III.A. Optimization of Site Layout................................................................................................................... 5
III.A.1. Limitation of development envelope - none 5
III.A.2. Preservation of natural drainage features - none 5
III.A.3. Setbacks from creeks, wetlands, and riparian habitats - no nearby creeks, wetlands or
riparian habitats. 5
III.A.4. Minimization of imperviousness -The project proposes only the necessary amount of
impervious surface to provide adequate parking & sidewalks for proposed buildings. 5
III.A.5. Use of drainage as a design element - we are using direct infiltration where feasible on
the site. 5
III.B. Use of Permeable Pavements - none..................................................................................................... 5
III.C. Dispersal of Runoff to Pervious Areas- all of the site will drain to the underground infiltration
systems. 5
III.D. Stormwater Control Measures - the entirety of the project's stormwater will be treated with
underground infiltration chambers .....................
IV.
Documentation of Drainage Design.............................................................................. 5
W.A. Descriptions of each Drainage Management Area............................................................................... 5
IV.A.1. Table of Drainage Management Areas 5
IV.A.2. Drainage Management Area Descriptions 5
W.B. Tabulation and Sizing Calculations....................................................................................................... 6
IV.B.1. Information Summary for LID Facility Design 6
IV.B.2. Self -Treating Areas 6
IV.B.3. Self -Retaining Areas 6
IV.B.4. Areas Draining to Stormwater Control Measure Facilities 6
V.
Source Control Measures.............................................................................................. 7
V.A. Site activities and potential sources of pollutants................................................................................. 7
V.B. Source Control Table.............................................................................................................................. 7
VI.
Stormwater Facility Maintenance.................................................................................. 8
VI.A. Ownership and Responsibility for Maintenance in Perpetuity ........................................................... 8
VI.B. Summary of Maintenance Requirements for Each Stormwater Facility ............................................. 8
VII.
Construction Checklist ............................................... ................. 9
.................................
VIII.
Certifications................................................................................................................ 9
Tables
Table 1. Project Data 1
Table IV.B.1 Information Summary for LID Facility Design
Table V.B Sources and Source Control Measures 4
Table x. Construction Plan C.3 Checklist 10
Figures
Vicinity Map x
Attachments
Stormwater Control Plan Exhibit
Stormwater Control Measures Sizing Calculator (submit Excel file)
Hydromodification
Certifications
Maintenance and inspection checklists
Appendices
This Stormwater Control Plan was prepared using the template dated 18 February 2014 [draft].
I. Project Data
Table 1. Project Data
Project Name/Number
Gilroy Nissan
APN 841-74-002, -003, -004
Application Submittal Date
February 2019
Owner
Blam jade LP
PO Box 1431
Visalia, CA 93279
Project Location
6807 Automall Parkway
Gilroy, CA
Project Phase No.
n/a
Project Type and Description
Zoning: HC Highway Commercial
Proposed Land Use: Automobile Dealership
Total Project Site Area (acres)
3.04 Ac
Total New Impervious Surface Area
114,868 sf
Total Replaced Impervious Surface Area
2,665 sf
Total Pre -Project Impervious Surface Area
5,118 sf
Total Post Project Impervious Surface Area
122,651 sf
Net Impervious Area
122,651 sf
Watershed Management Zone(s)
1
Design Storm Frequency and Depth
95th percentile 24 hr storm, depth =1.5 in
Urban Sustainability Area
No
II. Setting
II.A. Project Location and Description
The Gilroy Nissan Project is located on Automall Parkway in Gilroy, CA. The project proposed a new
paved lot, building and associated improvements. This property resides under the Central Coast
Regional Water Control Board Watershed and must comply with Central Coast Resolution R3-2013-
0032. The resolution outlines 4 levels of stormwater management based on the size of the project.
These four- levels of performance requirement, and their design criteria, are outlined below:
GILROY NISSAN - BLAM-JADE LP PAGE 1 OF 15 FEBRUARY 2019
Performance Requirement # 1
Projects subject to Performance Control Requirement No. 1 (PCR- 1) Site Design and Runoff
Reduction are projects that create and/or replace > 2,500 square feet of impervious surface
(collectively over the entire project site), including detached single- family homes. PCR- 1
requires the use of site design LID strategies. Projects are required to implement at least the
following measures:
• Limit disturbance of creeks and natural drainage features
• Minimize compaction of highly permeable soils
• Limit clearing and grading of native vegetation
• Minimize impervious surfaces
• Minimize stormwater runoff by implementing one or more of the following site
design measures:
o Direct roof runoff into cisterns or rain barrels for reuse
o Direct roof runoff onto vegetated areas
o Direct runoff from sidewalks, walkways, and/or patios onto vegetated areas
o Direct runoff from driveways and/or uncovered parking lots onto vegetated
areas
o Construct bike lanes, driveways, uncovered parking lots, sidewalks,
walkways and patios with permeable surfaces
When dispersing runoff to landscape areas, ensure it is safely away from building
foundations and footings, consistent with the California Building Code.
The Project Engineer must submit a stamped and signed copy of the Performance
Requirement No. 1 Certification, as included in Appendix A, stating that LID design
strategies are included in the project design.
Performance Control Requirement #2
Projects subject to Performance Control Requirement No. 2 (PCR- 2) Water Quality Treatment
are:
• Projects with z 5,000 square feet (sO of Net Impervious Area, except detached single family
homes.
• Detached single- family homes > 15,000 sf of Net Impervious Area.
A summary of the approved treatment measures and their design criteria can are provided in Table
2 below. These requirements must be met in addition to the requirements of PCR 1.
Table 2. Water Quality Treatment Measures and Design Criteria for PCR #2
Water Quality Treatment Measure
Design Criteria
LID Treatment System -
Retain stormwater runoff from 85tii
Harvesting and use, infiltration,
percentile 24- hour storm event (based on
evapotranspiration, and bioretention
local rainfall data)
(without an underdrain) SCMs
GILROY NISSAN - BLAM-JADE LP PAGE 2 OF 15 FEBRUARY 2019
Biofiltration Treatment System -
Design rain event of 0.2 in/hr intensity OR
Bioretention with raised underdrain, or other
2 x 85d, percentile hourly rainfall intensity
facilities at least as effective as a system with
Other specified design criteria include:
the specified design criteria
• Maximum surface loading rate 5
in/hr
• Minimum surface reservoir depth
(6»)
• Minimum planting medium depth
(24")
• Proper plant selection
• Subsurface gravel layer (minimum
depth of 12")
• Underdrain placement near top of
gravellayer
• No compaction of soils beneath
facility
• No liners preventing infiltration
Non- Retention Based Treatment Systems
Volume Hydraulic Design Basis:
-
85tI, percentile 24- hr storm event
Lined Bioretention, flow- through planters,
Flow Hydraulic Design Basis:
and high rate tree well filters and media
0.2 in/hr intensity OR
filters
2 x 85t>> percentile hourly rainfall intensity
Performance Requirement #3
Regulated Projects subject to Performance Requirement No. 3 (PR- 3) Runoff Retention are:
• Projects that create and/or replace > 15,000 sf of impervious surface, except detached
single- family homes
• Detached single- family homes with > 15,000 sf of Net Impervious Area (as defined in
PR- 2)
These requirements apply to Regulated Projects located in the following areas:
• watershed Management Zones (WMZs) 1, 2, 5, 6, 8 and 9; and
• Portions of WMZs 4, 7, and 10 that overlie designated Groundwater Basins.
This project lays in Watershed Management Zone 9 and therefore is required to implement
rainwater harvesting by either, infiltration, and/or evapotranspiration, prevent offsite discharge
from events up to the 85th percentile 24- hour rainfall event as determined from local rainfall
data.
Regulated Projects subject to PR- 3 must also meet PR- 1 and PR- 2 requirements and submit
PCR- 1 and PCR- 2 Certifications.
GILROY NISSAN - RLAM-JADE LP PAGE 3 OF 15 FEBRUARY 2019
Performance Requirement #4
Regulated Projects subject to Performance Requirement No. 4 (PR- 4) Peak Management are:
• Projects that create and/or replace >22,500 square feet of impervious surface
(collectively over the entire project site); and are In Watershed Management Zones 1, 2,3,
d, and 9
Given that this property is located in Watershed Management Zone 9, and is creating more than
22,500 square feet of impervious surface PCR-4 will have to be meet.
PCR- 4 requires the applicant to manage post- development peak flows discharged from the site.
The Project Engineer shall provide a Hydrology Report demonstrating that post- development
stormwater runoff peak flows discharged from the site do not exceed pre- project peak flows for
the 2-through 25-year storm events.
Orifice details and calculations used for controlled release of stormwater from the site are provided
in the Attachments.
Regulated Projects subject to PR- 4 must also meet PR- 1, PR- 2 and PR- 3 requirements and
submit Performance Requirement No. 1, 2 and 3 Certifications
11.13. Existing Site Features and Conditions
The existing site is currently undeveloped. Grass vegetation exists throughout the site. Approximately
5,118 sf of curb and gutter exist along the eastern frontage of the property. There are not any natural
areas, wetlands or watercourses in the site. There are no exiting structures that are to be removed
from site, but some of the existing curb and gutter will be removed and replace with driveway
approaches for entering and exiting purposes.
II.C. Opportunities and Constraints for Stormwater Control
The site constraints are generally the buildings and setbacks to the building foundation. All
treatment facilities need to be 10 feet minimum from any foundation. The site has an infiltration
rate of 1.5 in/hr. There are no known wells within 100 feet of the proposed infiltration chamber
locations.
GILRO`.� NISSAN -- BLAM-JADE LP PAGE 4 O; 15 FEBRUARCY 2019
III. Low Impact Development Design Strategies
III.A.Optimization of Site Layout
III.A.1. Limitation of development envelope - none
III.A.2. Preservation of natural drainage features - none
III.A.3. Setbacks from creeks, wetlands, and riparian habitats - no nearby creeks, wetlands or
riparian habitats.
III.A.4. Minimization of imperviousness - The project proposes only the necessary amount of
impervious surface to provide adequate parking & sidewalks for proposed buildings.
III.A.5. Use of drainage as a design element - we are using direct infiltration where feasible on the
site.
III.B. Use of Permeable Pavements - none
III.C. Dispersal of Runoff to Pervious Areas- all of the site will drain to the underground
infiltration systems.
I. D. Stormwater Control Measures - the entirety of the project's stormwater will be treated with
underground infiltration chambers.
IV. Documentation of Drainage Design
N.A. Descriptions of each Drainage Management Area
W.A.1. Table of Drainage Management Areas
DMA Area (square feet)
Name Surface Type
DMA 1
Building, Parking, Sidewalks
3501
D1VIA 2
Building, Parking, Sidewalks
7%067
IV.A.2.
Drainage Management Area Descriptions
DMA 1, totaling 35,801 square feet, drains rooftop, parking lot, and sidewalk. DMA 1 drains to
SCM 1 which is an underground infiltration chamber. Water will enter the infiltration chambers
through the onsite storm drain system. Any stormwater volume that exceeds the required treatment
GILROY NISSAN - ELAM-JADE LP PAGE 5 OF 15 FEBRUARY 2019
and hydro modification volume will enter the public storm system through the chamber's outlet
structure.
DMA 2, totaling 79,067 square feet of parking stalls and drive aisle. DMA 2 drains to SCM 2 which
is an underground infiltration chamber. Water will enter the infiltration chambers through the onsite
storm drain system. Any stormwater volume that exceeds the required treatment and hydro
modification volume will enter the public storm system through the chamber's outlet structure.
W.B.Tabulation and Sizing Calculations
IV.B.1. Information Summary for LID Facility Design
Total Project Disturbance Area
(Square Feet)
114,868 sf
Design Storm Depth
1.5 in
Applicable Requirements
Tier 1- 4
IV.13.2. Self7reating Areas
1000 a
IV.B.3. Self -Retaining Areas
none
IV.13.4. Areas Draining to Stormwater Control Measure Facilities
The site drains to underground detention chambers which where sized to store and infiltrate the 95"'
percentile, 24-hour storm event per Tier 3 requirements located in WMZ 1. Any stormwater volume
in excess of the 95"' percentile storm will be stored in the chambers and released at rates consistent
with Tier 4 requirements. Any additional stormwater volume will be allowed to enter the existing City
storm system through an overflow structure.
Stormwater Infiltration pits consisting of StormTech MG3500 & StormTech SG310 storage
chambers and drain rock with a porosity of 40% - will be used to meet tier 3 infiltration
requirements. Analyzing the percolation test results conducted by Earth System, an infiltration rate of
1.5 inches per hour was used for chamber sizing. The percolation test results can be found attached.
Infiltration facilities have been sized to ensure that water captured for detention will infiltrate into the
native soil within 72 hours of a rain event.
Stormwater to be infiltrated will be stored in the rock along with the StormTech infiltration
chambers. The remaining volume available in the chambers will be used for Tier - 4 hydro
modification and flood control storage and will release through control orifices before entering the
public storm system. These orifices have been size so that flows leaving the site will match the pre,
development 2-year and 10-year rain events. Orifice calculations are included in the
hydromodification calculations attached
GILROY NISSAN - BLAM-JADE LP PAGE 6 OF 15 FEBRUARY 2019
See plans for cross section of facilities.
See Stormwater Control Measures Sizing Calculator for DMA sizes and SCM measures, attached
below.
DMA # 1 Required Storage per Central Coast Region Stormwater Control Measure Sizing Calculator
Total Size of
# of Chambers
Tier 3
Tier 4
Total
Total Storage
SCM # 1
(SG310)
Retention
Retention
Storage
Provided in
Required
Required
Required
Chambers
3,082 sf
110
1,816 cf
1,874 cf
3,690 cf
4,056 cf
Using the storage volume tables provided in the attached for the StormTech SG310 specifications
sheet (with an extra 2 inches of stone cover) the total available storage for SCM 1 is 4,056 CF. This
exceeds that 1,816 cf of storage required that needs to be infiltrated and the 3,690 cf that needs to be
retained in order mitigate the outflow rate per tier 4 requirements.
DMA #2 Required Storage per Central Coast Region Stormwater Control Measure Sizing Calculator
Total Size of
# of Chambers
Tier 3
Tier 4
Total
Total Storage
SCM #2
(MG3500)
Retention
Retention
Storage
Provided in
Required
Required
Required
Chambers
3,697 sf
48
5,700 cf
5,813 cf
11,513 cf
11,690 cf
Using the storage volume tables provided in the attached for the StormTech MG3500 specifications
sheet (with an extra 2 inches of stone cover) the total available storage for SCM 2 is 11,690 CF. This
exceeds that 5,813 cf of storage required that needs to be infiltrated and the 11,513 cf that needs to
be retained in order mitigate the outflow rate per tier 4 requirements.
V. Source Control Measures
V.A. Site activities and potential sources of pollutants
V.B. Source Control Table
Potential source of
Permanent
Operational
runoff pollutants
source control BMPs
source control BMPs
Onsite storm drain
Mark inlets with "No Dumping.
Maintain and periodically
inlet (unauthorized
Flows to Creek"
repaint or replace markings.
non-storm,%vater
discharges)
GILROY NISSAN - BLAM-JADE LP PAGE 7 OF 15 FEBRUARY 2019
Landscape Outdoor
Pesticide use
'reserve existing native trees, shrubs,
nd ground cover to the maximum
xtent possible.
)esign landscaping to minimize
.rigation and runoff, to promote
urface infiltration where
pppopriate, and to minimize the use
�f fertilizers and pesticides that can
ontribute to storm -water pollution.
There landscaped areas are used to
etain or detain stormwater, specify
slants that are tolerant of saturated
oil conditions.
.der using pest -resistant plants,
ially adjacent to handscape.
To insure successful establishment,
select plants appropriate to site
soils, slopes, climate, sun, wind,
rain, land use, air movement,
ecological consistency, and plant
interactions.
VI. Stormwater Facility Maintenance
Maintain landscaping using
minimum or no pesticides.
See applicable operational BMPs
in Fact Sheet SC-41, `Building
and Grounds Maintenance," in
the CASQA Stormwater Quality
Handbooks see appendix
Provide IPM information to
new owners, lessees and
operators.
VI.A. Ownership and Responsibility for Maintenance in Perpetuity
The owner and their successors (1) a commitment to execute any necessary agreements, and (2) a
statement accepting responsibility for operation and maintenance of facilities until that responsibility
is formally transferred.
VI.B.Summary of Maintenance Requirements for Each Stormwater Facility
The project site proposes one type of storm water treatment facilities: Stormtech infiltration
chambers.
Stormtech Infiltration Chambers - Maintenance includes cleaning of the isolator row as required by
the manufacturer. This is completed by a jet vac.
GILROY NISSAN - BLAM-JADE LP PAGE 8 OF 15 FEBRU,'1RY 2019
VII. Construction Checklist
Stormwater
Control
Plan See Plan Sheet
Page # BMP Description #s
9 Stormwater Management Plan d
VIII. Certifications
Please see attachment for certifications
GILROY NISSAN - BLAM-JADE LP PAGE 9 OF 15 FEBRUARY 2019
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Project name: Tierra Ventures LLC
Project location: 67 Au 80t.mdII Parkway Gilroy, CA
Tier 2/Tier 3: 1 Tier 3 - Reten
Total project area (ft2):
Total new impervious area (f:2):
Total replaced impervious in a USA (ft2):
Total replaced impervious not in a USA (ft2):
Totalprojectimpervious area (ft2): 114868
New impervious area (ft2): 114868
Replaced impervious within a USA (f:2): 0
Replaced impervious not in a USA (ft2): 0
Total pervious/landscape area (ft2): 0
.„s Amu
s
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re eam =.
SCM 1 Direct Infiltration 2 Site -Specific 1.5 3082
SCM 2 Direct Infiltration 2 Site -Specific 1.5 3697
SCS Type I Distribution (10-min) SCS Type I Distribution (2-min)
Step
Minute
Cummulative
Distribution
Incremental
Distribution
0
0
0
0.0000
1
10
0.0027
0.0027
2
20
0.0053
0.0026
3
30
0.008
0.0027
4
40
0.011
0.0030
5
50
0.014
0.0030
6
60
0.017
0.0030
7
70
0.02
0.0030
8
80
0.023
0.0030
9
90
0.026
0.0030
10
100
0.029
0.0030
11
110
0.032
0.0030
12
120
0.035
0.0030
13
130
0.0383
0.0033
14
140
0.0417
0.0034
15
150
0.045
0.0033
16
160
0.0483
0.0033
17
170
0.0517
0.0034
18
180
0.055
0.0033
19
190
0.0583
0.0033
20
200
0.0617
0.0034
21
210
0.065
0.0033
22
220
0.0687
0.0037
23
230
0.0723
0.0036
24
240
0.076
0.0037
25
250
0.0797
0.0037
26
260
0.0833
0.0036
27
270
0.087
0.0037
28
280
0.091
0.0040
29
290
0.095
0.0040
30
300
0.099
0.0040
31
310
0.1033
0.0043
32
320
0.1077
0.0044
33
330
0.112
0.0043
34
340
0.1163
0.0043
35
350
0.1207
0.0044
36
360
0.125
0.0043
37
370
0.13
0.0050
38
380
0.135
0.0050
39
390
0.14
0.0050
40
400
0.1453
0.0053
41
410
0.1507
0.0054
42
420
0.156
0.0053
43
430
0.162
0.0060
44
440
0.168
0.0060
45
450
0.174
0.0060
46
4601
0.18071
0.0067
47
4701
0.18731
0.0066
Step
Minute
Cummulative
Distribution
Incremental
Distribution
0
0
0
0.0000
1
2
0.0005
0.0005
2
4
0.0011
0.0006
3
6
0.0016
0.0005
4
8
0.0021
0.0005
5
10
0.0027
0.0006
6
12
0.0032
0.0005
7
14
0.0037
0.0005
8
16
0.0043
0.0006
9
18
0.0048
0.0005
10
20
0.0053
0.0005
11
22
0.0059
0.0006
12
24
0.0064
0.0005
13
26
0.0069
0.0005
14
28
0.0075
0.0006
15
30
0.008
0.0005
16
32
0.0086
0.0006
17
34
0.0092
0.0006
18
36
0.0098
0.0006
19
38
0.0104
0.0006
20
40
0.011
0.0006
21
42
0.0116
0.0006
22
44
0.0122
0.0006
23
46
0.0128
0.0006
24
48
0.0134
0.0006
25
50
0.014
0.0006
26
52
0.0146
0.0006
27
54
0.0152
0.0006
28
56
0.0158
0.0006
29
58
0.0164
0.0006
30
60
0.017
0.0006
31
62
0.0176
0.0006
32
64
0.0182
0.0006
33
66
0.0188
0.0006
34
68
0.0194
0.0006
35
70
0.02
0.0006
36
72
0.0206
0.0006
37
74
0.0212
0.0006
38
76
0.0218
0.0006
39
78
0.0224
0.0006
40
80
0.023
0.0006
41
82
0.0236
0.0006
42
84
0.0242
0.0006
43
86
0.0248
0.0006
44
88
0.0254
0.0006
45
90
0.026
0.0006
46
92
0.02661
0.0006
471
941
0.02721
0.0006
Stormwater Runoff and Routing Equations:
Computing Runoff (SCS and SBUH are the same):
R = (P — la)2
P —la+S
Ia = 0.2S
R = (P — 0.2S) 2
P — 0.8S
1000
S= CN —10
where:
R = runoff (in)
P = rainfall (in)
la = initial abstraction (in)
S = potential maximum soil moisture retention after runoff begins (in)
CN = runoff curve number
SBUH Runoff Routing:
_ Rt x A 1
It dt x12x60
Qt+1 = Qt + w[It + It+1 — 2QJ
dt
w — (2Tc + dt)
_ 0.0 0 7 (nL) 0-8
TC (P2)0.5 x S0.4
where:
It = instantaneous hydrograph (cfs)
Rt = runoff for current time step (in)
A = contributing area (ft)
dt = calculation time step (min)
Qt = routed stormwater flow
w = routing function
Tc = time of concentration
n = Manning's roughness (0.011 for pavement)
L = flow lenth (ft; computed from tributary area)
P2 = 2-year, 24-hour rainfall (in)
s = 0.005 (ft/ft; assumed value)
Note: set minimum Tc = 5 minutes (Portland BES recomrr
from TR-55 user manual...
Chapter 3
Sheet flow
Tine of Concentration and Travel Time Texhnical fteteMW 55
t.'rbwx tlydrerloW rm Small water i
Sheet now is flow over pbute szttrfnees. it usually
oc.cun in the headwarer of streams. With shut flow,
the friction value (Manning's n) is an effective rough-
ness c oefTceent that. inc:lud" the effect of raindrop
iinpae t. drag over the plate surface; obstacles such as
litter, crop ridges, and rocks; still erosion and trans-
portation of sedhnent. Ths—w it values are for very
shallow How depths of about. 0.1 f(x)t or sir. Table 3-1
gives Mantting's n value,. for sheet now for wariotts
surface conditions.
Table 3-1 Roughness coeMrienttt (i9antting'sn) for
sheet now
Surface descripticni it V
Smooth surfaces (concreae, w4flualt,
gravel, or tare. sail) ........................................
0.01.1
Fallow (no residue) ................
5
Cultivated scads:
Residtx. MWV--3lili..........................................
0.06
Residua cover >Aft .........................................
0.17
Grass.:
Short grass prairie ............................................
0.15
thnige grwwws V................................................
0.24
Berntudiigr~ass..................................................
0.41
1ixnge (natural.)..........................................................
0.1:3
W(x)ds:W
tight underbritsh.............................................. 0.40
Dmsr underbmLch............................................ 0.80
t no n tiatlura are a conrtxxdte. of lnformntion omnpiled by Eng. ma ►
(19"),
a tnrludau xperie % rwrh as welting tovegra m, trhw%n ms, buffalo
grwa, blue gnuna grass:, and native gnctr mixtmms.
S Wwn .wleeKing n. consider cover to alit fight of about.0-1 ft. Thlx
is ibex only }taut of the plani nwer that will otxnrurt sheet flow.
For sheet flow of less titan 3W feet, use Manning s.
kinentatic solution (Overtop mid Meadows 1976) to
compute Tr:
Te (pn)a SO-4(� 3.31
whet* -
Tr = travel time (hr),
it = Manning's roughness coefficient (table 3-1)
L = flow length (ft)
P. = 2-year, 24-hoar rainfall (€n)
s = slope of hydraul€c grade line
(land slope, ft/ft)
This simplified forte of the Mannirtg's klneinat.ie solu-
tion. is b.w.-d on they following: (I)shallow -.®r ej env
unlfonn flow, (2) constant Intensity of rainfall, excess
(that part of a rain available for runoff), (3) rainfall
duration of 24 hvuts, and (4) wdnor effect of infiltra-
tion on travel time. Rainfall depth catt be obtained
from appendix B.
Shallow concentrated flow
After a ntaxitnunt of 300 feet, sheet draw tv; iaily be -
mines shallow concentrated now. The average veloc.
ity for this float' can be deterntined front figure :3-1, in
which average velocity is a function of watercourse
slope and type of channel. For rtiopes lee: 4 ttttut 0.00S
ftlft, uce ecltrat.ictrrs given in :yskxrtttlix F for figure. :3-1.
'tillage can affect the direction o€'shal.low coneen-
trated flow. 1•'luw =y not always be direc:tlyy down the
watershed xiolx• if tillage runes arro ss the :spree.
After deterntining average velocity In figure 3-1, use
equation 3-1 to estintat,e travel tune for the shallow
concentrated flow segment.
Open channels
()pen channels are assumed to begin where surveyed
t.xow; st tion infortnation has lee -cell obtained, where
tiiannelsz art. vbdble on aerbil phologr lfts, c-#rwitere
!slue lines (indicating streams) appear on United States
Geological Survey (USGS) quadrangle sheets.
Nlanning's equation or water surface profile €nforuta.
ticm can be ttsed to e-stiniate average flow velocity.
Average flow velocity is usually determined for bank -
full elevation-
SCM 1
Design rainfall depth (in)=
1.50
Plan ama(ft2)=:.
3082
Model time step (min)=
30
Sizing factor=
0.086
DMA Summary
Area(ff2)
CN
5
Weighting
Design infiltration rate (in/hr)=
1.5
New impervious area:
35801
98
0.20
1
Safety factor=
2
Replaced impervious In USA:
0
98
0.20
0
SCM ExOltration
rate ids)=
0.1070
Replaced
Impervious not USA:
0
98
0.20
0.5
Drainage
time (hours) =
0
landscape area:
0
68
4.71
1
Minimum
storage
volume (ft3)=
1816
Solid unit pavers set in sand:
0
69
114
1
Gravel
volume (ft3)=
4541
Non -runoff generating area:
0
N/A
N/A
N/A
Gravel depth(ft)=
1.5
Travel path length (ft)=
267.6
Time
of concentration (min) =
6.8
irair✓mroii
.roiri�+n,;,if)
is mn;'ru:»;':
n;,If w
v85"t
Jderrom.i
is±xhitmred
inioti iomr voi.J
8556
Si:
42X
385.3
1405E
22X
i
Impervious
landscape
Solid unit pavers set in sand
Cumulative
Time
Distribution Rainfall Depth
Cumulative
Runoff Depth
Instantaneous
Cumulative Runoff
Instantaneous
Cumulative Runoff
Instantaneous
Instantaneous
Routed Flow
Stormwater
6xflltratlon
Waretendon Water
(minutes)
(Type l) (in)
Rurfallfln)
(in)
R.m.ff(in)
Depth (in)
Runofflln)
Depth (in)
R.m.ff(in)
Runoff Rate ids)
Rate(ds)
Inflow(M)
Direct Rain(ft3)
Outflowift3)
Volume IRS)
0
D.WW 0.0000
O.ODDO
0.0000
DODW
0.0000
0.0000
DOOD0
0.0000
0.0000
0.0000
O.W00
0.0000
O.OWO
0.0000
10
0.0027 0.0041
0.0041
0.0000
0.0000
0.0000
0.0000
0.0000
O.ODW
o.ODDO
0.0000
0.0000
1.0402
-1.0402
0.0000
20
0.0026 0.0039
0.0060
0.0000
0.0000
0.0000
0.0000
0.0000
O.00W
0.0000
0.0000
0.0000
1.Cl
-1.0017
0.0000
30
O.W27 0.0041
0.0120
0.0000
O.ODW
O.OWO
O.DOW
0.0000
0.0000
0.0000
0.0000
0A000
1.0402
-1.0402
0.0000
40
O.W3D 0.W45
0.010
0.0000
O.00W
0.0000
0.0W0
DA
0.0000
0.001
0.0000
O.ODW
1.1558
-1.1558
0.0000
50
0.0030 0.0045
0.0210
O.OD00
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
1.1558
-1.1558
0.0000
60
O.W30 0.0045
0.0255
0.C(=
0.0000
0.0000
O.ODW
DODO)
0.0000
O.WW
O.00W
O.000D
1.1558
-1.1558
0.0000
70
0.0030 O.W45
0.0300
O.OWO
0.0000
0.0000
0.0000
O.G000
0.0000
0.0
0.0000
0.0000
1.1558
-1.1558
0.0000
80
O.W30 0.0045
D.0345
0.0000
0.0000
O.W00
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
1.1558
-1.2558
O.WW
90
0.0030 O.W45
0.0390
0.0000
O.ODW
0.0000
DOWD
0.000D
0.0000
O.000O
0.OWO
O.ODW
1.1558
-1.1558
0.0000
SOD
0.0030 0.0045
0.0435
0.0000
0.0000
0.0000
0.0000
0.0000
O.OWO
0.0002
0.0001
0.0441
1.1558
-1.1999
0.0000
110
0.0030 0.0045
0.0480
0.0002
O.OW2
0.0000
0.0000
0.0000
0.0000
O.W10
0.0005
0.3162
1.1558
-1.4719
0.0000
120
O.W30 0.0045
0.0525
0.0006
0.0004
0.0000
0.0000
O.G000
0.0000
0.0019
0.0013
0.W52
1.1558
-1.9609
0.0000
130
0.0033 0.0050
0.0575
0.0013
0.0006
0.0000
0.0000
0.GDM
DOWD
0.G031
0.0023
1.4001
1.2713
-2.6715
DOWD
140
0.0034 0.0051
0.0626
O.W21
O.OW8
0.D000
O.WW
0.0000
0.00W
O.OD42
0.0034
2.0597
1.30519
-3.3695
0.0000
150
0.0033 0.0050
0.0675
O.W31
0.0010
0.0000
O.WW
O.OD00
0.0000
0.0049
O.DO"
2.6314
1.2713
-3.9027
DOI=
1W
O.W33 0.01350
0.0725
O.W42
0.0012
0.0000
O.000O
0.0D00
O.00DO
O.W58
O.W52
3.1250
1.2713
4.3964
0.0000
170
O.W34 0.0051
0.0776
0.0056
O.W34
0.0000
O.00W
0.000o
DODDO
O.W68
O.W61
3.6509
1.3099
-4.9708
0.0000
180
O.W33 0.0050
0.0825
O.W71
0.01135
O.0W0
0.0000
0.0000
0.0000
0.0073
0.0069
4.1302
1.2713
-5.4016
0.0000
190
0.0033 0.0050
O.W75
0.0087
0.0016
0.0000
O.DOW
0.0G0D
0.0000
OA(80
0.0075
4.5129
1.2713
-5.7841
0.0000
200
O.W34 0.0051
O.W26
0.0105
O.W18
0.0000
O.00W
DOD()0
0.000)
D0009
O.W83
4.9779
1.3099
-6.2877
O.OD00
210
0.0033 0.0050
0.0975
0.0123
0.0019
0.0000
O.W00
0.0000
0.0000
0.0092
0.0090
5.3714
1.2713
4.6427
O.G000
220
O.W37 0.0055
0.1031
0.0145
0.0022
0.0000
0.0000
0.0000
DOOM
0.0110
0.0100
5.9797
1.4254
-7.4052
0.0000
230
0.0036 0.0054
0.1085
0.0168
0.0023
OA000
0.0000
DCODD
O.WW
0.0114
0.0110
6.6193
1.3869
-8.062
O.WW
240
0.0037 0.0055
0.1140
0.0193
0.0025
0.0GW
0.0000
0.0000
0.000
0.0123
0.0117
7.0454
1.4254
-8.4709
0.0000
250
0.0037 0.0055
0.1196
0.0219
0.0026
0.00D0
0.0000
0.0000
0.0000
0.0129
0.0125
7.5027
1.4254
-8.9281
O.O0G0
260
0.0036 O.W54
OA250
0.0246
0.0026
O.G000
0.0000
0.00W
0.0000
0.0131
0.0130
7.7731
1.3369
-9.1600
O.0000
270
O.W37 O.0G55
0.1305
0.0274
O.W28
DOCCO
O.ODW
0.0000
DOWD
0.0140
0.0135
8.0897
1.4254
i.5151
0.0000
280
0.0040 O.W50
0.1365
0.0305
O.W32
DCKIOO
0.0000
0.0OW
0.0000
0.0157
0.0147
8.7980
1.5410
-10.3390
0.0000
290
0.0040 O.W60
0.1425
0.0338
0.0033
O.00DO
0.0000
0.0000
0.0000
0.0163
0.0158
9.4796
1.5410
-11.02%
0.0000
30)
0.0040 O.WW
0.1435
0.0372
O.W34
0.0000
D()OOO
0.0000
0.0000
0.0168
0.0164
9.9563
1.5410
-11.3973
O.0000
310
0.0043 0.1:1065
0.1550
0.0409
O.W37
0.0000
0.0000
0.0000
0.0000
0.0186
0.0175
10.5068
1.6566
-12.1634
DA
320
0.0044 O.W66
0.1616
0.0449
0.0339
D.0000
0.0000
0.0000
0.0000
0.0196
0.0189
11.3169
1.6951
-13.0120
O.WW
330
O.W43 DOD65
0.1680
0.0488
O.W40
0.0000
ODDDD
0.0000
0.000O
0.0197
0.0195
11.7064
1.6566
-13.3630
0.0000
340
0.0043 0.0065
0.1745
0.0529
0.W40
DOWD
0.0000
0.0000
O.OWO
0.0201
0.0198
11.9021
1.6566
-135587
0.0000
350
0.0044 O'Gi
0.1811
0.0571
0.0042
0.0000
0.0000
0.0000
0.0000
0.0211
D.O205
12.2897
1.6951
-13.9848
O.OWO
360
0.043 0.0065
0.1875
0.0613
0.0042
0.0000
0.0300
0.0000
0.0000
0.0210
0.0210
12,5723
1.6566
-14.2289
O.WDD
SCM 2
Design rainfall depth (in)=
1.50
Plan area (U)=
`-3697
Model time step (min)=
30
Sizing factor=
0.047
DMASummary
Are.(ft2)
CN
S
Weighting
Design infiltration rate (m/hr)=
1.5
Newlmperviousarea:
79067
98
0.20
1
Safetyfac[or=
2
Replaced Impervious In USA:
0
98
0.20
0
SCM Ezflltratlon sate lets)=
0.1284
Replaced impervious not USA:
0
98
0.20
0.5
Drainage time (hours)=
1
Landscape area:
0
68
4.71
1
Minimum storage volume (ft3)=
5700
Solid unit pavers set In sand:
0
89
1.24
1
Gravel volume (ft3(=
14251
Non -runoff generating area:
0
N/A
N/A
N/A
Gravel depth (R)=
3.9
Travel path length (ft)-
397.7
1 •.,.,�
Time
Of Concentration(min)-
n3
IM'ifr%rtinCfr)
1%1!n,m:l0%i'
nCyf y,
u83%
'direct .,in •r
.,.c..
42r.
46ZI
Impervious
landsape
Solid unit paversset
in and
Cmnule-,
Time
Distribution Rainfall Depth
Cumulative
Rmmff Depth
Instantaneous
Cumulative Runoff
Instantaneous Cumulative
Runoff
Instantaneous
Instantaneous
Routed Flaw
Stormvnter
&filtration
(minutes)
(Type 1) (in)
"trial (in)
(in)
Runoff I.)
Depth(In)
Runoff(in)
Depthfin)
Hunoff(m)
Runoff Rate left)
Rate(ct)
Infa.(W)
Direct Rain(ft3l
OutRowlft3i
o
0.0000 0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0il
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
10
0.0027 0.0041
0.0041
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
1.2477
-1.2477
20
0.0026 0.0039
0.0080
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
1.2015
-1.2015
30
0.0027 0.0041
0.0120
0.0000
0.0000
0.0000
0.0000
O.00DO
O.00DO
0,OD00
OADOO
0.0000
1.2477
-1.2477
40
0.0030 0.0045
0.0165
0.000D
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
1.3864
-1.3864
50
0.0030 0.0045
0.0210
0.0000
0.0000
0.0000
0.0000
O.0D00
0.0000
0.OD00
0.0000
0.0000
13864
-1.3864
GO
0.0030 0.0045
0.0255
0.000D
0.0000
O.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
1.3864
-1.3864
70
0.0030 0.0045
0.0300
0.0000
0.0000
0.OD00
0.0000
0.0000
0.0000
O.OD00
0.0000
0.0000
1.39"
-1.38"
80
0.0030 0.0045
0.0345
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
1.38"
-1.3864
90
0.0030 0.0045
0.0390
0.0000
0.0000
0.0000
0.0000
O.D000
O.OD00
0.0000
0.0000
D.00D0
1.3864
-1.3864
300
0.0030 O.D045
0.0435
0.0000
0.0000
0.OD00
0.0000
0.0000
0.0000
0.0004
0.0002
0.0975
1.3864
-1.4839
110
0.0030 0.0045
0.0480
0.0002
O.00D2
0.000D
0.0000
0.0000
0.0000
0.0023
0.00111
0.6983
1.3864
-2.0847
120
0.0030 0.0045
0.0525
0.0006
0.0004
0.0000
0.0000
O.ODOO
0.0000
0.0043
0.0030
1.7782
1.3864
-3.1646
130
0.0033 0.0050
0.0575
0.0013
0.0006
0.0000
0.0000
0.0000
0.OD00
0.0068
0.0052
3.0922
1.5250
4.6173
140
0.0034 O.OD51
0.0626
0.0021
0.0008
0.0000
0.0000
0.0000
0.0000
0.0092
0.0076
4.5489
1.5712
-6.1201
ISO
0.0033 0.0050
0.0675
0.0031
0.0010
0.0000
0.0000
0.00DO
0.0000
0.0109
0.0097
5.8115
1.5250
-7.3365
160
0.0033 0.0050
0.0725
0.0042
0.0012
0.001
O.000D
040000
0.0000
0.0127
0.0115
6.9017
1.5250
-8.4267
170
0.0034 0.0051
0.0776
0.0056
0.0014
0.0000
0.000D
0.0000
0.0000
0.0149
0.0135
8.0852
1.5712
-9.6565
180
0.0033 0.0050
0.0825
0.0071
0.0015
9.0000
0.0000
0.0000
O.OD00
0.0161
0.0152
9.1217
1.5250
-10.6467
190
0.0033 0.0050
0.0875
0.0037
0.0016
0.0000
0.0000
0.0000
0.0000
0.0176
0.0166
9.9665
1.5250
-11.4915
30D
0.0034 0.0051
0.0926
0.0105
0.0A18
0.0000
0.0000
0.0000
0.0000
0.0196
0.0183
10.9937
1.5712
-12.5649
210
0.0033 0.0050
0.0975
0,0123
0.0019
O.0o00
0.0000
0.0000
010000
0.0204
0.0198
11.8629
1.5250
-13.3879
220
0.0037 0.0055
0.1031
0.0145
0.0022
0.0000
0.0000
0.0000
0.0000
0.0244
D.O220
13.2063
1.7099
-14.9162
230
0.0036 0.0054
0.1085
0.0168
0.0023
0.0000
0.0000
0.0000
0.0000
0.0252
0.0244
14.6189
1.6637
-16.M25
240
0,0037 0.0055
0.1140
0.0193
0.0025
0,0000
0.001
0.0000
0.0000
0.0273
0.0259
15.5599
1.7099
-17.2698
250
0.0037 0.0055
0.1196
0.0219
0.0026
O.0000
0.001
0.0000
0.0000
0.0286
0.0276
16.5698
1.7099
-18.2797
260
0.0036 0.0054
0.1250
0.0246
0.0026
0.0000
0,0000
0.0000
0.0000
0.0290
0.0286
17.1670
1.6637
-18.8306
270
0.0037 0.0055
0.1305
0.0274
0.0028
0,0000
0.(g100
0.0000
0.0000
0.0310
0.0298
17.8661
1.7099
-19.57W
280
0.0040 0.0060
0.1365
0.0305
0.0032
0,0000
0,0000
0.0000
0.0000
0.0347
0.0324
19.4306
1.8485
-21.2791
290
0.0040 0.0060
0.1425
0.0338
0.0033
0,0000
0.0000
0.0000
0.0000
0.0359
0.0349
20.9359
3.8485
-22.7844
300
0.0040 0.0060
0.1485
0.0372
0.0034
0.0000
0.0000
0.0000
0.D000
0.0371
0.030
21.7679
1.8485
-23.6163
310
0.0043 0.0065
0.1550
0.0409
0.0037
0.0000
0.0000
0.0000
0.0000
0.0411
0.0387
23.2w
1.9871
-25.1915
320
0.0044 0.0066
0.1616
0.0449
0.0039
0.0000
D.OWO
0.0000
0.0000
0.0433
0.0417
24.9934
2.0334
-27.W68
330
0.0C43 0.0065
0.1680
0.0488
O."o
0.0000
0.0000
0.0000
0.000D
0.0434
0.0431
25.11537
1.9871
-27.8406
340
0.0043 0.0065
0.1745
0.0529
0.0040
0.0000
0.0000
0.0000
0.0000
0.0445
0.0438
26.2860
1.9871
-28.2731
350
0.0044 0.0066
0.1811
0.0571
0.0042
0.0000
0.00DO
0.0000
0.0000
0.0465
0.0452
27.1421
2.0334
-29.1754
360
0.0043 0.0065
0.1875
0.0613
0.0042
0.0000
0.000D
0.0000
0.0000
0.0464
0.0463
27.7662
1.9871
-29.7533
Lookup Tables for Combo
Boxes
DMA Type
Code
Self -Treating
STA
Self -Retaining
SRA
Drains to SCM
2SCM
Drains to Self -Retaining
2SRA
SCM Type
Bioretention
Direct Infiltration
DMA Surface Types
Curve Number
Runoff Factor (WQ)
Roof
98
0.9
Concrete or asphalt
98
0.9
Grouted unit pavers
98
0.9
Pervious concrete
0.0
Porous asphalt
0.0
Unit pavers set in sand
89
0.2
Open/porous pavers
0.0
Crushed aggregate
0.0
Turfblock
0.0
Landscape
68
0.1
SCM Optimization
Area
Depth
USA Lookup
Yes
No
Compliance Approach
Tier 2 - Treatment
Tier 3 - Retention
Infiltration Rate
HSG A/B
HSG C/D
Site -Specific
Impervious Type Code
New NEW
Replaced RPL
Replaced within a USA RUSA
Hydraulic Constants
Gravel layer porosity: 0.4
0
5
0
n
P
r t-
O
E
�+
Drainage Analysis - (Predevelopment) 2-year storm
Area =
0.8219 AC
Length of Travel (L) =
171.08 LF
Difference in Elevation (H) =
2.25 FT
Effective Slope Line =
0.013152 FT/FT
Tc = 0.0078*(LA2/S)"0.385 +10 =
12.2 min
MAP 19
Rainfall Intensity
2 yr storm from table B-1.
T (min) A
B
10 0.1665
0.0025'-
12.2 0.1709
0.0025
15 0.1766
0.0032
Depth = A+B(MAP)
x = 0.2183 at 12.2 min
Intensity: I = x/D
1.0764 in/hr
C value given per 2005 City Standards for parks and natural ground
Rate of Runoff
Q2(pre) = Cpre I A
C = 0.10
I = 1.08
Q2 (pre) = 0.088 cfs
Restrictor size for outlet from bioretention chambers
Q from orfice
= Cd * A * (2gh)^.5
1.3
" diameter restriction
A
= 0.01
Cd
= 0.60
h
= 4.54
Q
= 0.088 cfs
Draina-ge Analysis - (Post development)
Rainfall Intensity
2 yr storm from table B-1.
Tc =
12.1670
_T (min)
A
B
10
0.1665
0.0020
12.2
0.1709
0.0025
15
0.1766
0.0032
C _value per 2012 C.3 Stormwater Handbook
c-value acres
Hardscape 1.00 0.8219
Landscape 0.1 0
1.00
Depth = A+B(MAP)
x = 0.2183 inch at 12.2 min
Intensity I = x/D
1.0764 in/hr
Rate of Runoff
Q200st) = Cpost I A
C = 1.00
I = 1.08
Q2 (post) = 0.88 cfs
Drainage Analvsis - (Predevelopmenti 5-vear storm
Area =
0.8219 AC
Length of Travel (L) =
171.08 LF
Difference in Elevation (H) =
2.25 FT
Effective Slope Line =
0.013152 FT/FT
Tc = 0.0078*(LA2/S)"0.385 +10 =
12.2 min
MAP 19
Rainfall Intensity
5 yr storm from table B-1.
T (min) A
B
10 0.2285
0.0028
12.2 0.2378
0.0033
15 0.2500
0.0040
Depth = A+B(MAP)
x = 0.3007 at
12.2 min
Intensity: I = x/D
1.4831
in/hr
C value given per 2005 City Standards for parks and natural ground
Rate of Runoff
Q5(pre) = Cpre I A
C =
0.10
I =
1.48
Q5 (pre) =
0.12 cfs
Drainage Analysis - (Post development)
Rainfall Intensity
5 yr storm from table B-1.
Tc =
12.1670
T (min) A
B
10 0.2285
0.0028
12.2 0.2378
0.0033
15 0.2500
0.0040
C _value per 2012 C.3 Stormwater Handbook
c-value
acres
Roof 1.00
0.8219
Landscape 0.1
0
1.00
Depth = A+B(MAP)
x = 0.3007 inch at 12.2 min
Intensity I = x/D
1.4831 in/hr
Rate of Runoff
Qs(post) = Cpost I A
C = 1.00
I = 1.48
Q5 (post) = 1.22 cfs
Drainage Analysis - (Predevelooment)10-vear storm
Area =
0.8219 AC
Length of Travel (L) =
171.08 LF
Difference in Elevation (H) =
2.25 FT
Effective Slope Line =
0.013152 FT/FT
Tc = 0.0078*(L^2/S)^0.385 +10 =
12.2 min
MAP 19
Rainfall Intensity
10 yr storm from table 13-1.
T (min) A
B
10 0.2587
0.0036
12.2 0.2743
0.0041
15 0.2948
0.0047
Depth = A+B(MAP)
x = 0.3515 at
12.2 min
Intensity: I = x/D
1.7336 in/hr
C value given per 2005 City Standards for parks and natural ground
Rate of Runoff
Qio(pre) = Cpre I A
C = 0.10
= 1.73
Q10 (pre) = 0.14 cfs
010 (pre)- 02 (pre) - 0.054 cfs
Restrictor size for outlet from bloretention chambers
Q from orfice
= Cd * A * (2gh)^.5
1.7
" diameter restriction
A
= 0.02
Cd
= 0.60
h
= 0.50
Q
= 0.054 cfs
Drainage Analysis - (Post development)
Rainfall Intensity
10 yr storm from table 13-1.
Tc =
12.1670
Amin)
A
B
10
0.2587
0.0036
12.2
0.2743
0.0041
15
0.2948
0.0047
C _value per 2012 C.3 Stormwater Handbook
c-value
acres
Hardscape
1.00
0.8219
Landscape
0.1
0
1.00
Depth = A+B(MAP)
x = 0.3515 inch at 12.2 min
Intensity I = x/D
1.7336 inmr
Rate of Runoff
Qio(post) = Cpost I A
C = 1.00
I = 1.73
Q10 (post) = 1.42 cfs
2-year Storm: Pre and Post Pond Size
Area =
0.8219
acre
Outflow =
0.09
cfs
MAP =
19
inch
Infiltration rate
1.5
in/hour
Infiltration area
3082
ftz
QINFILTRATION
0.1070139
cfs
MAP
=19"
2 r Depth
Voume In
Infiltration
Volume Out
Storage
T
A
B
(in)
(ft)
(ft)
(ft)
(ft)
5 min
0.120194
0.001385
0.146509
502.6755
32.10417
26.54
444.03
10 min
0.166507
0.001956
0.203671
698.7996
64.20833
53.08
581.51
15 min
0.176618
0.003181
0.237057
813.3477
96.3125
79.63
637.41
30 min
0.212497
0.00595
0.325547
1116.959
192.625
159.25
765.08
1 hr
0.253885
0.010792
0.458933
1574.609
385.25
318.50
870.86
2 hr
0.330848
0.019418
0.69979
2400.995
770.5
637.01
993.49
3 hr
0.374053
0.027327
0.893266
3064.815
1155.75
955.51
953.55
6 hr
0.425178
0.045735
1.294143
4440.233
2311.5
1911.02
217.71
12 hr
0.409397
0.069267
1.72547
5920.125
4623
3822.04
-2524.92
depth x = A+B(MAP)
Volume In = A*(C+0.15)*Depth/12*43560
C= 1.00
5-year Storm: Pre and Post Pond Size
Area =
0.8219
acre
Outflow =
0.12
cfs
MAP =
19
inch
Infiltration rate
1.5
in/hour
Infiltration area
3082
fe
QINFILTRATION
0.1070139
cfs
T
MAP =19"
5 r Depth
Voume In
Infiltration
Volume Out
Storage
A B
in
(ft)
(ft)
(ft)
(ft)
5 min
0.170347 0.001857
0.20563
705.521
32.10417
36.57
636.85
10 min
0.228482 0.002758
0.280884
963.7191
64.20833
73.14
826.37
15 min
0.250029 0.004036
0.326713
1120.959
96.3125
109.71
914.94
30 min
0.307588 0.007082
0.442146
1517.012
192.625
219.41
1104.98
1 hr
0.357109 0.0134
0.611709
2098.787
385.25
438.82
1274.71
2 hr
0.45184 0.024242
0.912438
3130.594
770.5
877.65
1482.45
3 hr
0.512583 0.034359
1.165404
3998.526
1155.75
1316.47
1526.30
6 hr
0.554937 0.060859
1.711258
5871.363
2311.5
2632.95
926.92
12 hr
0.562227 0.094871
2.364776
8113.597
4623
5265.89
-1775.29
depth x = A+B(MAP)
Volume In = A*(C+0.15)*Depth/12*43560
C= 1.00
10-year Storm: Pre and Post Pond Size
Area =
0.8219
acre
Outflow =
0.14
cfs
MAP =
19
inch
Infiltration rate
1.5
in/hour
Infiltration area
3082
ft2
QINFILTRATION
0.1070139
cfs
MAP
=19"
10 r Depth
Voume In
Infiltration
Volume Out
Storage
T
A
B
(in)
(ft)
(ft)
(ft)
(ft)
5 min
0.201876
0.002063
0.241073
827.1267
32.10417
42.75
752.28
10 min
0.258682
0.003569
0.326493
1120.205
64.20833
85.49
970.51
15 min
0.294808
0.00471
0.384298
1318.535
96.3125
128.24
1093.99
30 min
0.367861
0.007879
0.517562
1775.766
192.625
256.47
1326.67
1 hr
0.427723
0.014802
0.708961
2432.46
385.25
512.95
1534.26
2 hr
0.522608
0.027457
1.044291
3582.985
770.5
1025.89
1786.59
3 hr
0.59166
0.038944
1.331596
4568.735
1155.75
1538.84
1874.15 «
6 hr
0.625054
0.070715
1.968639
6754.443
2311.5
3077.68
1365.26
12 hr
0.641638
0.11166
2.763178
9480.523
4623
6155.36
-1297.83
depth x = A+B(MAP)
Volume In = A*(C+0.15)*Depth/12*43560
C= 1.00
StormTech SC-310 Chamber Pond
Sizing
Number of Chambers
Stone foundation
Stone cover
Storage needed to be infiltrated
2 year storm storage (plus infiltration volume)
5 year storm storage (plus infiltration volume)
10 year storm storage (plus infiltration volume)
110 chambers
6 inches
8 inches
1816 cf
2809.49 cf
3342.30 cf
3690.15 cf
Project: GILROY NISSAN-WEST BED
Chamber Model -
Units -
Number of chambers -
Voids in the stone (porosity) -
Base of STONE Elevation -
Amount of Stone Above Chambers -
Amount of Stone Below Chambers -
Area of system -
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sf Min. Area - 2609 sf min. area
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30
0.00
0.00
102.73
102.73
4056.17
191.67
29
0.00
0.00
102.73
102.73
3953.43
191.59
28
0.00
0.00
102.73
102.73
3850.70
191.50
27
0.00
0.00
102.73
102.73
3747.97
191.42
Top of 10 year storm
26
0.00
0.00
102.73
102.73
3645.23
191.34
191.37'
25
0.00
0.00
102.73
102.73
3542.50
191.25
24
0.00
0.00
102.73
102.73
3439.77
191.17 Top of 5 year storm
23
0.00
0.00
102.73
102.73
3337.03
191.09
191.09,
22
0.06
6.47
100.15
106.61
3234.30
191.00
21
0.15
17.02
95.93
112.94
3127.69
190.92
20
0.27
29.24
91.04
120.28
3014.74
190.84
19
0.54
59.93
78.76
138.69
2894.46
190.75 Top of 2 year storm
18
0.70
77.44
71.76
149.20
2755.77
190.67
190.70'
17
0.82
90.70
66.45
157.15
2606.57
190.59
16
0.92
101.70
62.05
163.75
2449.42
190.50
15
1.01
111.65
58.07
169.72
2285.67
190.42
14
1.09
120.40
54.57
174.97
2115.94
190.34
13
1.15
126.97
51.94
178.92
1940.97
190.25
95th ercentile de th
12
1.21
133.64
49.28
182.92
1762.05
190.17
190.19'
11
1.27
140.24
46.64
186.88
1579.13
190.09
10
1.32
145.70
44.45
190.15
1392.26
190.00
9
1.36
150.15
42.67
192.82
1202.10
189.92
8
1.40
154.55
40.91
195.46
1009.28
189.84
7
1.43
157.81
39.61
197.42
813.82
189.75
6
0.00
0.00
102.73
102.73
616.40
189.67
5
0.00
0.00
102.73
102.73
513.67
189.59
4
0.00
0.00
102.73
102.73
410.93
189.50
3
0.00
0.00
102.73
102.73
308.20
189.42
2
0.00
0.00
102.73
102.73
205.47
189.34
1
0.00
0.00
102.73
102.73
102.73
189.25
Project: Gilroy Nissan Date: 3/13/2019
JN: 18039
SUMMARY
The intent of this hydromodification drainage analysis is to match post development
runoff flow to 2 year pre development flow for small storms and to 10 year pre
development flow for larger storms. Using the Central Coast Region Stormwater Control
Measure Sizing Calculator, a required storage volume of 1816 cubic feet was calculated
in order to comply with Tier 3 retention requirements. An additional 1874 cubic feet of
required storaged was calcuated in order to comply with Tier 4 peak flow management.
This equates to a total volume of 3,690 cubic feet of required storage. 110 StormTech
SC-310 infiltration chambers will be used in order manage this required storage. 6 inches
of drain rock will be placed underneath the chamber and 8 inches of drain rock will be
placed as over head cover. The chamber system is designed to for a maximum capacity
of 4056 cubic feet of storage which exceeds the required volume. The runoff exitting the
chambers will be mitigated through a storm drain man hole with a restrictor plate. The
restrictor plate will have two orifices drilled into it. The first hole will be placed at the invert
of the manhole (elevation 186.83) and will be 1.3 inches in diameter allowing the pre
development 2 year storm run off flow of 0.088 cfs to exit the chambers. The second
hole will be place at elevation 191.37 and will be 1.7 inches in diameter. The two orifice
will work in conjunction to allow the 10 year development flow of 0.14 cfs to exit the
chamber system.
W.
r
O
0
0
rt
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0
9
FwJ
tm
Drainage Analysis - (Predevelopment) 2-year storm
Area =
1.815 AC
Length of Travel (L) =
197.02 LF
Difference in Elevation (H) =
0.833 FT
Effective Slope Line =
0.004228 FT/FT
Tc = 0.0078*(L"2/S)"0.385 +10 =
13.7 min
MAP 19
Rainfall Intensity
2 yr storm from table B-1.
T (min) A
B
10 0.1665
0.0020
13.7 0.1741
0.0029
15 0.1766
0.0032
Depth = A+B(MAP)
x = 0.2289 at
13.7 min
Intensity: I = x/D
0.9996 in/hr
C value given per 2005 City Standards for parks and natural ground
Rate of Runoff
Q2(pre) = Cpre I A
C = 0.10
I = 1.00
Q2 (pre) = 0.181 cfs
Restrictor size for outlet from bioretention chambers
Q from orrice
= Cd * A * (2gh)".5
1.9
" diameter restriction
A
= 0.02
Cd
= 0.60
h
= 3.96
Q
= 0.181 cfs
Drainage Analysis - (Post development)
Rainfall Intensity
2 yr storm from table B-1.
Tc =
13.7394
T (min) A
B
10 0.1665
0.0020
13.7 0.1741
0.0029
15 0.1766
0.0032
C _value per 2012 C.3 Stormwater Handbook
c-value acres
Hardscape 1.00 1.815
Landscape 0.1 0
1.00
Depth = A+B(MAP)
x = 0.2289 inch at 13.7 min
Intensity I = x/D
0.9996 in/hr
Rate of Runoff
Q2(post) = Cpost I A
C = 1.00
I = 1.00
Q2 (post) = 1.81 cfs
Drainage Analvsis - (Predevelonment) 5-vear storm
Area =
1.815 AC
Length of Travel (L) =
197.02 LF
Difference in Elevation (H) =
0.833 FT
Effective Slope Line =
0.004228 FT/FT
Tc = 0.0078*(L^2/S)^0.385 +10 =
13.7 min
MAP 19
Rainfall Intensity
5 yr storm from table B-1.
T (min) A
B
10 0.2285
0.0028
13.7 0.2446
0.0037
15 0.2500
0.0040
Depth = A+B(MAP)
x = 0.3152 at
13.7 min
Intensity: I = x/D
1.3763
in/hr
C value given per 2005 City Standards for parks and natural ground
Rate of Runoff
Qs(pre) = Cpre I A
C =
0.10
I =
1.38
Q5 (pre) =
0.25 cfs
Drainage Analysis - (Post development)
Rainfall Intensity
5 yr storm from table B-1.
Tc =
13.7394
T (min) A
B
10 0.2285
0.0028
13.7 0.2446
0.0037
15 0.2500
0.0040
C _value per 2012 C.3 Stormwater
Handbook
c-value
acres
Roof 1.00
1.815
Landscape 0.1
0
1.00
Depth = A+B(MAP)
x = 0.3152 inch at 13.7 min
Intensity I = x/D
1.3763 in/hr
Rate of Runoff
Qs(post) = Cpost I A
C = 1.00
I = 1.38
Q5 (post) = 2.50 cfs
Drainage Analysis - (Predeveloament)10-vear storm
Area =
1.815 AC
Length of Travel (L) =
197.02 LF
Difference in Elevation (H) =
0.833 FT
Effective Slope Line =
0.004228 FT/FT
Tc = 0.0078*(L^2/S)^0.385 +10 =
13.7 min
MAP 19
Rainfall Intensity
10 yr storm from table B-1.
T (min) A
B
10 0.2587
0.0036
13.7 0.2857
0.0044
15 0.2948
0.0047
Depth = A+B(MAP)
x = 0.3697
at 13.7 min
Intensity: I = x/D
1.6146
in/hr
C value given per 2005 City Standards for parks and natural ground
Rate of Runoff
Qlo(pre) = Cpre I A
C
= 0.10
I
= 1.61
Q10 (pre)
= 0.29 cfs
Q10 (pre)- Q2 (pre)
= 0.112 cfs
Restrictor size for outlet from bioretention chambers
Q from orfice
= Cd * A * (2gh)^.5
2.5
" diameter restriction
A
= 0.03
Cd
= 0.60
h
= 0.50
Q
= 0.112 cfs
Drainage Analysis - (Post development)
Rainfall Intensity
10 yr storm from table 13-1.
Tc =
13.7394
T (min)
A
B
10
0.2587
0.0036
13.7
0.2857
0.0044
15
0.2948
0.0047
C _value per 2012 C.3 Stormwater Handbook
c-value
acres
Hardscape
1.00
1.815
Landscape
0.1
0
1.00
Depth = A+B(MAP)
x = 0.3697 inch at 13.7 min
Intensity I = x/D
1.6146 in/hr
Rate of Runoff
Qlo(post) = Cpost I A
C = 1.00
I = 1.61
Q10 (post) = 2.93 cfs
2-year Storm: Pre and Post Pond Size
Area =
1.815
acre
Outflow =
0.18
cfs
MAP =
19
inch
Infiltration rate
1.5
in/hr
Infiltration area
3697
sf
QINFILTRATION
0.1283681
cfs
MAP
=19"
2 yr Depth
Voume In
Infiltration
Volume Out
Storage
T
A
B
(In)
(ft)
(ft)
(ft)
(ft)
5 min
0.120194
0.001385
0.146509
1110.057
38.51042
54.43
1017.12
10 min
0.166507
0.001956
0.203671
1543.158
77.02083
108.85
1357.28
15 min
0.176618
0.003181
0.237057
1796.114
115.5313
163.28
1517.30
30 min
0.212497
0.00595
0.325547
2466.578
231.0625
326.56
1908.95
1 hr
0.253885
0.010792
0.458933
3477.206
462.125
653.13
2361.95
2 hr
0.330848
0.019418
0.69979
5302.111
924.25
1306.25
3071.61
3 hr
0.374053
0.027327
0.893266
6768.024
1386.375
1959.38
3422.27
6 hr
0.425178
0.045735
1.294143
9805.356
2772.75
3918.76
3113.85
12 hr
0.409397
0.069267
1.72547
13073.4
5545.5
7837.52
-309.62
depth x = A+B(MAP)
Volume In = A*(C+0.15)*Depth/12*43560
C= 1.00
5-year Storm: Pre and Post Pond Size
Area =
Outflow =
MAP =
Infiltration rate
Infiltration area
QINFILTRATION
1.815 acre
0.25 cfs
19 inch
1.5 in/hr
3697 sf
0.1283681 cfs
T
MAP =19"
5 r Depth
Voume In
Infiltration
Volume Out
Storage
A B
in
(ft)
(ft)
(ft)
(ft)
5 min
0.170347 0.001857
0.20563
1558
38.51042
74.94
1444.55
10 min
0.228482 0.002758
0.280884
2128.179
77.02083
149.88
1901.28
15 min
0.250029 0.004036
0.326713
2475.412
115.5313
224.82
2135.06
30 min
0.307588 0.007082
0.442146
3350.015
231.0625
449.64
2669.32
1 hr
0.357109 0.0134
0.611709
4634.746
462.125
899.27
3273.35
2 hr
0.45184 0.024242
0.912438
6913.285
924.25
1798.54
4190.49
3 hr
0.512583 0.034359
1.165404
8829.937
1386.375
2697.82
4745.75
6 hr
0.554937 0.060859
1.711258
12965.72
2772.75
5395.63
4797.34
12 hr
0.562227 0.094871
2.364776
17917.24
5545.5
10791.27
1580.47
depth x = A+B(MAP)
Volume In = A*(C+0.15)*Depth/12*43560
C= 1.00
10-year Storm: Pre and Post Pond Size
Area =
1.815
acre
Outflow =
0.29
cfs
MAP =
19
inch
Infiltration rate
1.5
in/hr
Infiltration area
3697
sf
QINFILTRATION
0.1283681
cfs
MAP
=19"
10 r Depth
Voume In
Infiltration
Volume Out
Storage
T
A
B
(in)
(ft)
(ft)
(ft)
(ft)
5 min
0.201876
0.002063
0.241073
1826.542
38.51042
87.91
1700.12
10 min
0.258682
0.003569
0.326493
2473.745
77.02083
175.83
2220.90
15 min
0.294808
0.00471
0.384298
2911.717
115.5313
263.74
2532.44
30 min
0.367861
0.007879
0.517562
3921.421
231.0625
527.48
3162.87
1 hr
0.427723
0.014802
0.708961
5371.597
462.125
1054.97
3854.50
2 hr
0.522608
0.027457
1.044291
7912.298
924.25
2109.94
4878.11
3 hr
0.59166
0.038944
1.331596
10089.13
1386.375
3164.91
5537.84
6 hr
0.625054
0.070715
1.968639
14915.82
2772.75
6329.82
5813.25 «
12 hr
0.641638
0.11166
2.763178
20935.82
5545.5
12659.63
2730.68
depth x = A+B(MAP)
Volume In = A*(C+0.15)*Depth/12*43560
C= 1.00
StormTech MC-3500 Chamber Pond
Sizing
Number of Chambers
Stone foundation
Stone cover
Storage needed to be infiltrated
2 year storm storage (plus infiltration volume)
5 year storm storage (plus infiltration volume)
10 year storm storage (plus infiltration volume)
48 chambers
9 inches
14 inches
5700 cf
9122.27 cf
10497.34 cf
11513.25 cf
Project: GILROY NISSAN-EAST BED
Chamber Model -
Units -
Number of Chambers -
Number of End Caps -
Voids in the stone (porosity) -
Base of STONE Elevation -
Amount of Stone Above Chambers -
Amount of Stone Below Chambers -
Area of system -
St®rmTech
Q{ndude Pertme[es Srone In Cal[ulatlons
Min. Area - 2735 sf min, area
Height of
System
(inches)
Incremental Single
Chamber
cubic"--)
Incremental
Single End Cap
I (cubicifeet)
In- mental `
Chambers
(Cubic feed
incremental
End Cap
cubic fae0
incremental
Slone
(cubic feet)
Incremental Ch,
EC and Slone
{cubic feet
Cumulative
System
(cubic feel)
Elevation
(feet)
68 0.00
0.00
0.00
0.00
123.23
123.23
11689.92
191.08
67 0.00
0.00
0.00
0.00
123.23
123.23
11566.69
190.99
Top of 10 year storm
66 0.00
0.00
0.00
0.00
123.23
123.23__'_7i�j.qo
�ivu.wi
190.96'
65 0.00
0.00
0.00
0.00
123.23
123.23
11320.22
190-83
64 0.00
0.00
0.00
0.00
123.23
123.23
11196.99
190.74
63 0.00
0.00
0.00
0.00
123,23
123.23
11073.76
190.66
62 0.00
0.00
0.00
0.00
123.23
123.23
10950.52
190.58
fit 0.00
0.00
0.00
0.00
123.23
123.23
10827.29
190.49
60 0.00
0.00
0.00
0.00
123.23
123.23
10704.06
190AI
59 0.00
0.00
0.00
0.00
123.23
123.23
10580.82
190.33
Top of 5 year storm
5B 0.00
0.00
0.00
0.00
123.23
123.23
10457.59
190.24
190.27'
57 0.00
0.00
0.00
0.00
123.23
123.23
10334.36
190.16
56 0.00
0.00
0.00
0.00
123.23
123.23
10211.12
190.08
55 0.00
0.00
0.00
0.00
123.23
123.23
10087.89
189.99
54 0.06
0.00
2.79
0.00
122.12
124.91
9964.66
189.91
53 0.19
0.02
9.32
0.36
119.35
129.05
9839.75
189.83
52 0.29
0.04
14.11
0.60
117.35
132.06
9710.70
189.74
51 0.40
0.05
19.38
0.82
115.15
135.35
9578.64
189.66
50 0.69
0.07
32.98
1.08
109.61
143.67
9443.28
189.58
49 1.03
0.09
49.36
1.41
102.93
153.70
9299.61
189.49
4B 1.25
0.11
59.98
1.71
98.56
160.25
9145.92
189.41
47 1.42
0.13
68.27
2.02
95.12
165.41
8985.67
189.33
TOE of 2 year storm
46 1.57
0.14
75.51
2.31
92.10
169.93
auzu.zu
llai.24
189.40'
45 1.71
0.16
81.94
2.61
89.41
173.96
8650.34
189.16
44 1.83
0.18
87.77
2.91
86.96
177.64
8476.37
189.08
43 1.94
0.20
93.01
3.21
84.74
180.97
8298.73
188.99
42 2.04
0.22
UT96
3.49
82.65
164.10
8117.77
188.91
41 2.13
0.23
102.47
3.76
80.74
186.97
7933.66
188.83
40 2.22
0.25
106.76
4.01
78.92
189.70
7746.70
188.74
39 2.31
0,27
110.73
4.25
77.24
192.22
7557.00
188.66
38 2.38
0.28
114.47
4.48
75.65
194.60
7364.78
188.58
37 2.46
0.29
118.04
4.70
74.14
196.88
7170.1E
188.49
36 2.53
0.31
121.35
4.93
72.72
199.00
6073.30
188.41
35 2.59
0.32
124.50
5.14
71.38
201.02
6774.30
188.33
34 2.66
0.33
127.49
5.35
70.10
202.94
6573.29
188.24
33 2.72
0.35
130.33
5.55
68.88
204.76
6370.35
188.16
32 2.77
0.36
133.02
5.76
67.72
206.50
6165.59
188.08
31 2.82
0.37
135.58
5.96
66.62
208.16
5959.08
187.99
30 2.88
0.38
138.02
6.15
65.56
209.74
5750.93
187.91
95th,percentile depth
29 2.92
0.40
140.30
6.34
6456
211.25
SM1.19i9783
187 89'
28 2.97
0.41
142.55
6.52
63.60
212.68
5329.94
187.74
27 3.01
0.42
144.60
6.70
62.71
214.01
5117.26
187.66
26 3.05
0.43
146.56
6.87
61.86
215.29
4903.25
187.58
25 3.09
0.44
148.53
7.05
61.00
216.58
4687.96
187.49
24 3.13
0.45
150.27
7.21
60.24
217.72
4471.38
187.41
23 3.17
0.46
151.95
7.37
59.50
218.83
4253.66
187.33
22 3.20
0A7
153.57
7.53
5B.79
219.90
4034.83
187.24
21 3.23
0.48
155.09
7.68
58.12
220.90
3814.94
167.16
20 3.26
0.49
156.56
7.83
57.48
221.88
3594.04
187.08
19 3.29
0.50
157.93
7.97
56.87
222.77
3372.18
186.99
18 3.32
0.51
159.26
8,10
56.29
223.65
3149.41
186.91
17 3.34
0.51
160.52
8.23
55.73
224.48
2925.75
186.83
16 3.37
0.52
161.69
8.36
55.21
225.26
2701.27
186.74
15 3.39
0.53
162.84
8.47
54.71
226.02
2476.01
186.66
14 3.41
0.54
183.90
8.56
54.24
226.72
2249.99
186.58
13 3.44
0.54
164.9E
8.69
53.77
227.43
2023.26
186.49
12 3.46
0.55
165.97
8.79
53.33
228.09
1795.83
186.41
11 3.48
0.56
166.98
8.88
52.89
228.75
1567.74
166.33
10 3.51
0.59
168.24
9.52
52.13
229.89
1338.99
186.24
9 0.00
0.00
0.00
0.00
123.23
123.23
1109.10
186.16
8 0.00
0.00
0.00
0.00
123.23
123.23
985.87
186.08
7 0.00
0.00
0.00
0.00
123.23
123.23
862.63
185.99
6 0.00
0.00
0.00
0.00
123.23
123.23
739.40
185.91
5 0.00
0.00
0.00
0.00
123.23
123.23
616.17
185.83
4 0.00
0.00
0.00
0.00
123.23
123.23
492.93
185.74
3 0.00
0.00
0.00
0.00
123.23
123.23
369.70
185.66
2 0.00
0.00
0.00
0.00
123.23
123.23
246.47
185.58
1 0.00
0.00
0.00
0.00
123.23
123.23
123.23
185.49
Project: Gilroy Nissan Date: 3/13/2019
JN: 18039
SUMMARY
The intent of this hydromodification drainage analysis is to match post development
runoff flow to 2 year pre development flow for small storms and to 10 year pre
development flow for larger storms. Using the Central Coast Region Stormwater Control
Measure Sizing Calculator, a required storage volume of 5700 cubic feet was calculated
in order to comply with Tier 3 retention requirements. An additional 5813 cubic feet of
required storaged was calcuated in order to comply with Tier 4 peak flow management.
This equates to a total volume of 11,513 cubic feet of required storage. 48 StormTech
MC-3500 infiltration chambers will be used in order manage this required storage. 9
inches of drain rock will be placed underneath the chamber and 14 inches of drain rock
will be placed as over head cover. The chamber system is designed to for a maximum
capacity of 11,690 cubic feet of storage which exceeds the required volume. The runoff
exitting the chambers will be mitigated through a storm drain man hole with a restrictor
plate. The restrictor plate will have two orifices drilled into it. The first hole will be placed
at the invert of the manhole (elevation 187.00) and will be 1.9 inches in diameter allowing
the pre development 2 year storm run off flow of 0.181 cfs to exit the chambers. The
second hole will be place at elevation 190.96 and will be 2.5 inches in diameter. The two
orifice will work in conjunction to allow the 10 year development flow of 0.29 cfs to exit
the chamber system.
n
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l:7
5
Post Construction Stormwater Management Requirements
Performance Requirement No. .1-- Certification
File No.:
PERFORMANCE REQUIREMENT NO. 1: SITE DESIGN AND RUNOFF REDUCTION
Certification
DESIGN STRATEGY INCORPORATED
INTO PROJECT?
1. Limit disturbance of creeks and natural drainage features. F�
2. Minimize compaction of highly permeable soils. R
3. Limit clearing and grading of native vegetation at the site to the minimum Fv]
area needed to build the project, allow access, and provide fire protection.
4. Minimize impervious surfaces by concentrating improvements on the least
sensitive areas of the site, while leaving the remaining land in a natural
undisturbed state.
5. Minimize stormwater runoff by implementing one or more of the following FV1
design measures:
a) Direct roof runoff into cisterns or rain barrels for reuse. ❑
b) Direct roof runoff onto vegetated areas safely away from building RV
foundations and footings.
c) Direct runoff from sidewalks, walkways, and/or patios onto vegetated a
areas safely away from building foundations and footings.
d) Direct runoff from driveways and/or uncovered parking lots onto Fie]
vegetated areas safely away from building foundations and footings.
e) Construct bike lanes, driveways, uncovered parking lots, sidewalks,
walkways, and patios with permeable surfaces.
I, Amanda Musy-Verdel acting as the Project Engineer for Blam-Jade LP
project, located at 6807 Automall Parkway Gilroy, CA hereby state that the Site
Design and Runoff Reduction design strategies indicated above have been incorporated into the design
project.
ature
2-h.�Ila
Date
4 REV 6/11/15
Post Construction Stormwater Management Requirements
Performance Requirement No. 2 — Certification
File No.:
PERFORMANCE REQUIREMENT NO. 2: WATER QUALITY TREATMENT
Certification
ON -SITE WATER QUALITY TREATMENT MEASURES INCORPORATED?
1. Low Impact Development (LID) Treatment Systems designed to retain stormwater
runoff generated by the 851h percentile 24-hour storm. Stormwater Control
Measures Implement (check all that apply, design documentation is required)
a) Harvesting and Use, F-1
b) Infiltration, a
c) Evapotranspiration F I
2. Biofiltration Treatment Systems'— with the following design parameters:
a)
Maximum surface loading rate appropriate to prevent erosion, scour and
channeling within the biofiltration treatment system itself and equal to 5
inches per hour, based on the flow of runoff produced from a rain event equal
to or at least:
(a) 0.2 inches per hour intensity; or
(b) Two times the 85th percentile hourly rainfall intensity for the
applicable area, based on historical records of hourly rainfall
depth
b)
Minimum surface reservoir volume equal to the biofiltration treatment
system surface area times a depth of 6 inches
c)
Minimum planting medium depth of 24 inches. The planting medium must
sustain a minimum infiltration rate of 5 inches per hour throughout the life of
the project and must maximize runoff retention and pollutant removal. A
mixture of sand (60%-70%) meeting the specifications of American Society for
Testing and Materials (ASTM) C33 and compost (30%-40%) may be used. A
Project may utilize an alternative planting medium if it demonstrates its
planting medium is equal to or more effective at attenuating pollutants than
the specified planting medium mixture.
d)
Proper plant selection
e)
Subsurface drainage/storage (gravel) layer with an area equal to the
biofiltration treatment system surface area and having a minimum depth of
12 inches
f)
Underdrain with discharge elevation at top of gravel layer
F-1
g)
No compaction of soils beneath the biofiltration facility (ripping/loosening of
F-1
soils required if compacted)
6 REV 6/11/2015
Post Construction Stormwater Management Requirements
Source Control Checklist
File No..
h) No liners or other barriers interfering with infiltration, except for situations
where lateral infiltration is not technically feasible
3. Non -Retention Based Treatment Systems — designed to meet at least one of the
following hydraulic sizing criteria:
I,
(a) Volume Hydraulic Design Basis — Treatment systems whose primary
mode of action depends on volume capacity shall be designed to treat
stormwater runoff equal to the volume of runoff generated by the 85th
percentile 24-hour storm event, based on local rainfall data.
(b) Flow Hydraulic Design Basis —Treatment systems whose primary mode
of action depends on flow capacity shall be sized to treat:
(i) The flow of runoff produced by a rain event equal to at least two
times the 85th percentile hourly rainfall intensity for the
applicable area, based on historical records of hourly rainfall
depths; or
(ii) The flow of runoff resulting from a rain event equal to at least 0.2
inches per hour intensity.
Amanda Musy-Verdel
FE]
7
01
acting as the Project Engineer for Blam-Jade LP
project, located at 6807 Automall Parkway Gilroy, CA
hereby state that the Water
Quality Treatment Measures indicated above have been incorporated into the design of the
project.
Signature
Date
1 Facilities or a combination of facilities, of a different design than in Item #2 may be permitted if all of the
following measures of equivalent effectiveness are demonstrated:1) equal or greater amount of runoff infiltrated
or evapotranspired; 2) equal or lower pollutant concentrations in runoff that is discharged after biofiltration; 3)
equal or greater protection against shock loading and spills; and 4) equal or greater accessibility and ease of
inspection and maintenance.
z Technical guidance for designing bioretention facilities is available from the Central Coast LID Initiative. The
guidance includes design specifications and plant lists appropriate for the Central Coast climate.
(http://www.centralcoastlidi.org/Central_Coast LIDI/LID Structural_BMPs.htmi)
7 REV 6/11/15
Post Construction Stormwater Management Requirements
Performance Requirement No. 3 — Design Rainfall Events & Treatment Requirement for WMZs
PERFORMANCE REQUIREMENT NO. 3 — RUNOFF RETENTION
Design Rainfall Events & Treatment Requirements for
Watershed Management Zones (WMZs)1
Check
Applicable
WMZ2
Treatment Options & Design Rainfall
WMZs
WMZ 1
Via optimized infiltration 3, prevent offsite discharge from events up to the 951h
percentile 24-hour rainfall event as determined from local rainfall data.
WMZ 2
Via storage, rainwater harvesting, infiltration, and/or evapotranspiration, prevent
F]
offsite discharge from events up to the 951h percentile 24-hour rainfall event as
determined from local rainfall data.
WM 4 *
Via optimized infiltration 2, prevent offsite discharge from events up to the 95th
percentile 24-hour rainfall event as determined from local rainfall data.
F]
WMZ 5
Via optimized infiltration prevent offsite discharge from events up to the 85th
percentile 24-hour rainfall event as determined from local rainfall data.
WMZ 6
Via storage, rainwater harvesting, infiltration, and/or evapotranspiration, prevent
offsite discharge from events up to the 851h percentile 24-hour rainfall event as
determined from local rainfall data.
WMZ 9
Via storage, rainwater harvesting, infiltration, and/or evapotranspiration, prevent
offsite discharge from events up to the 851h percentile 24-hour rainfall event as
determined from local rainfall data.
WMZ 10 *
Via optimized infiltration 2, prevent offsite discharge from events up to the 95th
percentile 24-hour rainfall event as determined from local rainfall data
1. Includes only those WMZs located in Santa Clara County.
2. Use the Santa Clara County Department of Planning and Development Online Property Profile database to
determine the WMZ in which your project is located: http://www.sccplanning.org/gisprofile/
Search for your project site by APN or Address to retrieve the Property Profile. At the bottom of the property
profile page, under Special Resources/Hazards/Constraints Areas, look for the "Central Coast Watershed
Management Zone Value".
3. Storage, rainwater harvesting, and/or evapotranspiration may be used when infiltration is optimized.
* Applicable only to those areas that overlay designated Groundwater Basins.
8 REV 6/11/2015
Post Construction Stormwater Management Requirements
Performance Requirement No. 3 — LID Site Assessment Checklist File No.:_
PERFORMANCE REQUIREMENT NO.3 — RUNOFF RETENTION
LID Site Assessment Checklist
ITEMS TO DOCUMENT:
INCLUDED IN
PROJECT
DOCUMENTS?
1.
Site topography
2.
Hydrologic features including contiguous natural areas, wetlands,
watercourses, seeps, or springs
3.
Depth to seasonal high groundwater
a
4.
Locations of groundwater wells used for drinking water
FVI
5.
Depth to an impervious layer such as bedrock
FV/
6.
Presence of unique geology (e.g., karst)
7.
Geotechnical hazards
8.
Documented soil and/or groundwater contamination
9.
Soil types and hydrologic soil groups
W1
10.
Vegetative cover/trees
V
11.
Run-on characteristics (source and estimated runoff from offsite which
a
discharges to the project area)
12.
Existing drainage infrastructure for the site and nearby areas including the
W1
location of municipal storm drains
13.
Structures including retaining walls
W]
14.
Utilities
a
15.
Easements
W]
16.
Covenants
W]
17.
Zoning/Land Use
k/1
18.
Setbacks
W1
19.
Open space requirements
F7
20.
Other pertinent overlay(s)
9 REV 6/11/15
Post Construction Stormwater Management Requirements
Performance Requirement No. 3 — L10 Site Design Measures File No.:
PERFORMANCE REQUIREMENT NO.3 — RUNOFF RETENTION
LID Site Design Measures
The Project Engineer shall certify the Project design optimizes the use of the following design
measures to augment the design strategies required by Performance Requirement No.1. Initial
each runoff retention measure that has been incorporated and optimized into the design or mark
NA if not applicable.
PERFORMANCE REQUIREMENT NO.3 CERTIFICATION OF LID SITE DESIGN MEASURES
DESIGN MEASURE
INCORPORATED/
OPTIMIZED
1. Defining the development envelope, identifying the protected areas, and
identifying areas that are most suitable for development and areas to be X
left undisturbed
Z. Identifying conserved natural areas, including existing trees, other
vegetation, and soils (shown on the plans) N/A
3. Limit the overall impervious footprint of the project
4. Design of streets, sidewalks, or parking lot aisles to the minimum widths
necessary, provided that public safety or mobility uses are not X
compromised
5. Set back development from creeks, wetlands, and riparian habitats
N/A
6. Design conforms the site layout along natural landforms
X
7. Design avoids excessive grading and disturbance of vegetation and soils
X
I, Amanda Musy-Verdel acting as the Project Engineer for Blam-Jade LP
J g
project, located at 68Q7 Automall Parkway Gilroy, CA ,hereby state that LID Site
D n Measures initialed have been incorporated into the design of the project.
Signature Date
10 REV 6/11/15
in
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Sul
Earth Systems
500 Park Center Drive, Suite 1 I Hollister, CA 95023 1 Ph: $31,637.2133 1 www.earthsystems.com
January 24, 2019
Mr. Matt Graham
Graham & Associates
1005 N. Demaree Street
Visalia, CA 93291
PROJECT: GILROY NISSAN DEALERSHIP
CHESTNUT STREET, APNS 841-74-002, -003, AND -004
GILROY, CALIFORNIA
SUBJECT: Geotechnical Engineering Report
File No.: 302580-001
REF.: Proposal for a Geotechnical Engineering Investigation, Gilroy Nissan
Dealership, Chestnut Street, APNs 841-74-002, -003, and -004, Gilroy,
California, by Earth Systems Pacific, dated September 19, 2018
Dear Mr. Graham:
In accordance with your authorization of the above -referenced proposal, this geotechnical
engineering report was prepared for use in development of plans and specifications for the
planned new Nissan dealership on Chestnut Street in Gilroy. As shown on the Schematic Site
Plan by Scott & Associates, the building will contain a showroom, offices, a service center, and
related facilities. Plans for the building were not provided for our review, but we assumed that
the it will utilize a combination of structural steel and light frame elements and will have a
concrete floor slab -on -grade. Other site improvements include paved driveways and parking
spaces, exterior concrete flatwork, and landscape. Based on the site topography, we expect that
site grading will entail cuts and fills on the order of3 feet. It is likely that low impact development
(LID) features such as bioswales and/or underground storage/infiltration chambers will be
provided for control and treatment of stormwater runoff.
Scope of Services
The scope of work for the geotechnical engineering investigation included a general site
reconnaissance, subsurface exploration, laboratory testing of soil samples, engineering
evaluation of the data collected, and preparation of this report. To assess the potential
infiltration rates of the soil, relatively shallow percolation rate tests were conducted at the site.
The analysis and subsequent recommendations were based on the Schematic Site Plan by Scott
& Associates (Sheet 1.2, dated 08/09/2018), and on other information provided by the client.
.,, Gilroy Nissan Dealership January 24, 2019
Gilroy, California
The report and recommendations are intended to comply with the considerations of Sections
1803.1 through 1803.6, 1803.7 (portions of), J104.3 and J104.4 of the 2016 California Building
Code (CBC), and common geotechnical engineering practice in this area at this time under similar
conditions. The field and laboratory tests were performed in general conformance with the
standards noted, as modified by common geotechnical practice in this area at this time under
similar conditions.
Preliminary geotechnical recommendations for site preparation and grading, conventional
spread footings, drilled pier foundations, seismic design parameters, retaining walls, slabs -on -
grade and exterior flatwork, utility trenches, asphalt concrete pavement sections, site drainage
and finish improvements, and geotechnical observation and testing are presented to guide the
development of project plans and specifications. It is our intent that this report be used by the
client to form the geotechnical basis of the design of the project as described herein, and in the
preparation of plans and specifications.
Evaluation of the site geology; interpretation of the percolation test results; analysis of the soil
for mold or other microbial content, lead, asbestos, corrosion potential, radioisotopes,
hydrocarbons, or other chemical properties are beyond the scope of this report. This report does
not address issues in the domain of contractors such as, but not limited to, site safety, loss of
volume due to stripping of the site, shrinkage of soils during compaction, excavatability, shoring,
temporary slope angles, and construction means and methods. Ancillary features such as
temporary access roads, fences, light poles, effluent disposal systems, LID/BMP improvements,
and nonstructural fills are not within our scope and are also not addressed.
To verify that pertinent issues have been addressed and to aid in conformance with the intent of
this report, it is requested that grading and foundation plans be submitted to the geotechnical
engineer for review as they near completion. In the event that there are any changes in the
nature, design, or locations of improvements, or if any assumptions used in the preparation of
this report prove to be incorrect, the conclusions and recommendations contained herein shall
not be considered valid unless the changes are reviewed and the conclusions of this report are
verified or modified in writing by the geotechnical engineer. The criteria presented in this report
are considered preliminary until such time as they are verified or modified in writing by the
geotechnical engineer in the field during construction.
302580-001 2 1901-020.SER
Gilroy Nissan Dealership
Gilroy, California
Site Setting
January 24, 2019
The site, APNs 841-74-002, -003, and -004, is located on the western side of Chestnut Street,
approximately 800 feet south of East 10th Street, in Gilroy, California. At the time of the
investigation, the site and the adjacent parcels to the south were undeveloped. A review of
historic Google Earth images indicated that residences or other types of light structures were
present on the southwestern section of the site prior to 2003. Other nearby properties are
currently occupied by commercial and light industrial developments. The subject site is
essentially flat except for an approximately 4-foot high strip of stockpiled soil parallel to the
southern property line. Vegetation consists of a variable cover of weeds and grass, with a row
of trees along the northern edge of the parcel.
Subsurface Investigation and Laboratory Testing
The subsurface exploration consisted of eight borings drilled at the site on September 27, 2018.
The borings were advanced using a truck -mounted Simco drill rig, Model 2400 SK-1, equipped
with a 6-inch diameter, continuous -flight, solid -stem auger. The approximate boring locations
are shown on the attached Boring and Percolation Test Location Map.
Soils encountered in the borings were categorized and logged in general accordance with the
Unified Soil Classification System (ASTM D2488-17). Copies of the boring logs are attached. As
the borings were drilled, soil samples were obtained using an internally -lined barrel sampler
(ASTM D3550-17, with shoe similar to D2937-17), standard penetration tests were performed at
selected intervals (ASTM D1586-11), and bulk samples were obtained from the auger cuttings.
Selected liner samples were tested for unit weight and moisture (ASTM D2937-17, modified for
internal liners). One bulk sample and one liner sample were tested for particle size distribution
(ASTM D1140-17, D422-63/07) and plasticity index (ASTM D4318-17). Two liner samples were
tested for unconfined compressive strength (ASTM D2166-16), and one liner sample was tested
for one-dimensional consolidation (ASTM D 2435/D2435M-11). One bulk sample was also tested
for R-value (ASTM D-2844/D-2844M-13). Copies of the laboratory test results are attached.
General Subsurface Profile
In general, the soils encountered in the exploratory borings were mixtures of clays and sands that
contained variable percentages of gravel (CL, SC, and SW -SC). The predominantly fine-grained
302580-001 3 1901-020.SER
*��RWAWPTPGilroy Nissan Dealership
Gilroy, California
January 24, 2019
soils typically had medium stiff to very stiff consistencies. The predominantly coarse -grained
materials were generally medium dense, although zones of loose and dense soils were present
at various depths. Except for some slightly moist surface material, the soils were generally moist
at the time of drilling. Free subsurface water was not encountered within the 20-foot depth of
exploration.
Conclusions
Site Suitability: Based on the results of the field investigation and the laboratory testing program,
in our opinion, the site is geotechnically suitable for the proposed automobile dealership
provided that the recommendations contained herein are implemented in the design and
construction. The primary geotechnical considerations are the expansion potential of the upper
soil, the variable consistency of the near -surface material, and the presence of a stockpile of
undocumented fill at the site.
Soil Expansion Potential: A plasticity index test of a sample of the upper clayey sand resulted in
a liquid limit of 36 and a plasticity index of 20, indicating that the sample tested has a moderate
expansion potential. Expansive soils tend to swell with increases in soil moisture and shrink as
the soil moisture decreases. The volume changes that the soils undergo in this cyclical pattern
can stress and damage slabs, foundations, and other improvements if precautionary measures
are not incorporated into the design and construction procedures. The footings should be
deepened to the zone of lesser soil moisture fluctuation, and concrete slabs and exterior flatwork
should be protected by covering the slab and flatwork areas with nonexpansive imported
material. The soil should also be moisture conditioned during grading.
Site Grading: Removal of the stockpiled soil and removal (overexcavation) and replacement of
the upper native soil as compacted engineered fill are recommended to provide more uniform
support for foundations, floor slabs, and other improvements. The existing stockpiled material
should be reviewed by the geotechnical engineer at the time of grading to assess its suitability
for use as fill at the site.
Seismic Hazards: The site is not located in Santa Clara County geologic hazard zones for fault
rupture, landslides, or soil liquefaction, and potentially liquefiable soils were not encountered in
our exploratory borings. Thus, measures to mitigate potential soil liquefaction and other
302580-001 4 1901-020.SER
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geologic hazards are not considered necessary for the project. However, strong ground shaking
should be expected during the design life of the planned structure. At a minimum, the planned
improvements should be designed to resist seismic shaking in accordance with current California
Building Code (CBC) requirements. Seismic design parameters based on the 2016 Edition of the
CBC are presented later in the report.
Recommendations
Site Preparation and Grading
1. The site should be prepared for grading by removing existing trees and other vegetation,
large roots, debris and other potentially deleterious materials from areas to receive
improvements. The site preparation operations should be observed by the geotechnical
engineer prior to continuing grading.
2. Existing utility lines that will not remain in service should be either removed or
abandoned. The appropriate method of utility abandonment will depend upon the type,
depth, and location of the utility. Recommendations for abandonment can be made as
necessary.
3. The existing fill stockpile along the southern edge of the site should be entirely removed
to expose firm native material. The geotechnical engineer should observe the fill stockpile
removal and should assess the quality of the stockpiled material if it is to be used as fill
for the subject project.
4. In addition to removal of the fill stockpile, the soil in the building area and in areas to
receive exterior flatwork associated with the structure should be removed
(overexcavated) to minimum depths of 2 feet below existing grade, or to the planned
elevations of the footing bottoms, whichever is deeper. The overexcavated area should
extend a minimum of 5 feet beyond the planned building foundation perimeter, and 2
feet beyond the edges of exterior flatwork and other improvements adjacent to the
structure.
5. The overexcavation should be observed by the geotechnical engineer prior to continuing
grading. If buried objects, existing undocumented fill, soft soils, or other potentially
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Gilroy, California
adverse conditions are observed during overexcavation, additional depth of
overexcavation or other remedial measures may be recommended by the geotechnical
engineer.
6. The overexcavated surfaces should be cross -scarified to an approximate depth of 8
inches. The soil should then be moisture conditioned to a level slightly above optimum
moisture content and recompacted to a minimum of 90 percent of maximum dry density.
Other surfaces to receive fill and cut surfaces to receive improvements beyond the
building and flatwork areas should be scarified and recompacted in a similar manner.
7. The previously overexcavated material can be re -used as fill provided that it is cleared of
excessive quantities of potentially deleterious materials. Fill should be placed in moisture
conditioned lifts not exceeding 8 inches in loose thickness and compacted to a minimum
of 90 percent of maximum dry density. Large roots, rock, debris, and irreducible material
larger than 4 inches in diameter should be removed from the soil prior to compaction.
8. To help reduce the effects of soil expansion on floor slabs, a minimum of 12 inches of
nonexpansive material should be placed in the slab areas. The nonexpansive imported
material should be compacted to a minimum 90 percent of maximum dry density.
Nonexpansive import should also be used to reduce the effects of soil expansion on
exterior flatwork (refer to Slabs -on -grade and Exterior Flatwork).
9. Nonexpansive material is defined as being coarse grained (ASTM D 2487-17) with a
plasticity index (ASTM D 4318-17) of 10 or less. Proposed nonexpansive material should
be evaluated by the geotechnical engineer before being transported to the site, and on
an intermittent basis during placement on the site. Processed aggregate base would be
suitable for use as nonexpansive material. The slab and flatwork areas should be
periodically moistened as necessary prior to placement of the nonexpansive import to
maintain the soil moisture content above optimum.
10. If fill is to be imported for general use at the site (other than nonexpansive imported
material), the fill should be coarse grained with a plasticity index of 20 or less. Proposed
imported soils should be evaluated by the geotechnical engineer before being
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11 Gilroy Nissan Dealership January 24, 2019
Gilroy, California
transported to the site, and on an intermittent basis during placement and compaction
on the site.
11. Cut and fill slopes should not be steeperthan 2:1, measured horizontally to vertically.
Conventional Spread Footings
1. The structure can be supported by conventional spread footings bearing in firm
compacted soil. To penetrate through the zone most affected by soil expansion, the
footings should have minimum depths of 24 inches below lowest adjacent grade. All
footings should be reinforced as directed by the architect/engineer. The footing
excavations should be observed by the geotechnical engineer prior to placement of
formwork or reinforcement and should be moistened to close any desiccation cracks prior
to placement of concrete.
2. Footings should be designed using a maximum allowable bearing capacity of 2,000 psf
dead plus live load and a subgrade modulus (K30) of 60 psi/inch. The allowable bearing
capacity may be increased by one-third when transient loads such as wind or seismicity
are included. Using these criteria, longterm total and differential foundation settlements
are expected to be on the order of 1 inch and %: inch within 25 feet, respectively.
3. Resistance to lateral loads should be calculated based on a passive equivalent fluid
pressure of 300 pcf and a friction factor of 0.3. Passive and frictional resistance can be
combined in the calculations without reductions. These values are based on the
assumption that backfill adjacent to foundations is properly compacted.
Drilled Pier Foundations
1. As an alternative to the use of conventional spread footings, the structure can be
supported by drilled, cast -in -place reinforced concrete friction piers interconnected by
grade beams. The piers should have minimum diameters of 16 inches and should be
reinforced as directed by the architect/engineer. Minimum clear spacing between piers
should be 3 pier diameters. To help resist uplift forces on grade beams at garage door
openings, piers should be provided at maximum 8-foot spacings at the door openings.
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2. The piers should penetrate through any fill to be embedded a minimum of 8 feet into firm
native soil. The geotechnical engineer should be present during pier drilling operations
to observe the recommended penetration into firm native soil.
3. The piers should be designed to derive support from skin friction against the native soil;
end -bearing capacity of the piers, and skin friction in fill should be disregarded in the
calculations. Skin friction in the upper 2 feet of soil should be also disregarded due to
possible disturbance of the soil during drilling.
4. The native soil should be assigned a maximum allowable skin friction value of 600 psf for
downward loads and 400 psf for uplift loads. The allowable skin friction values may be
increased by one-third when transient loads such as wind or seismicity are included.
Using these values, total and differential settlements are expected to be on the order of
X-inch.
5. Lateral loads should be resisted by passive resistance of the native soil against the piers.
Passive resistance should be calculated based on an equivalent fluid pressure of 300 pcf
acting over two pier diameters. Due to possible disturbance of the soil during drilling,
lateral resistance in the upper 2 feet of soil should be neglected in the calculations.
6. The piers should not deviate from a plumb line by more than 2 percent of the pier length,
as measured from the top to the point of interest. Adequate pier oversize may be
assumed to provide the recommended tolerance. The bottoms of the pier excavations
should be firm and should not contain excessive loose debris and slough material. Loose
drilling spoils should be removed or compacted prior to placement of reinforcing steel.
7. All perimeter piers should be laterally restrained by concrete grade beams. The grade
beams should be reinforced as directed by the architect/engineer. The grade beam
excavations should be moistened to close any desiccation cracks prior to placement of
concrete.
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Seismic Design Parameters
1. The seismic design parameters for the site per Chapter 16 of the California Building Code
(2016 Edition) are as follows. The values were determined utilizing the SEAOC/OSHPD
web -based tool and the provisions of ASCE 7-10. The site coordinates were determined
using the Google Earth web site.
Site Class = D
Peak Ground Acceleration, PGA = 0.579 g
Short Term Spectral Acceleration Parameter, Ss=1.S17 g
1 Second Spectral Acceleration Parameter, S1= 0.615 g
Site Coefficient, Fa= 1.00
Site Coefficient, F = 1.50
Adjusted Spectral Acceleration Parameter, SMs=1.517 g
Adjusted Spectral Acceleration Parameter, Sml= 0.923 g
Design Spectral Acceleration Parameter, Sps= 1.011 g
Design Spectral Acceleration Parameter, Sol= 0.615 g
Retaining Walls
1. Retaining walls should be supported by conventional spread footings or drilled pier
foundations, designed and constructed in accordance with the recommendations
provided above.
2. The wall design should be based on the following parameters:
Active equivalent fluid pressure ........
At -rest equivalent fluid pressure .......
............................................45 pcf
...................................60 pcf
No surcharges are taken into consideration in the above values. If seismic forces are to
be considered in the retaining wall design, the seismic increment of earth pressure should
be 8H pounds per linear foot, where H is the height of the retained soil. The seismic
pressure should be applied uniformly on the back of the wall along the height of the
retained soil.
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3. Retaining wall backfill should be fully drained utilizing either a free draining gravel
blanket, permeable material, or a manufactured synthetic drainage system. Water from
the drainage medium should be collected and discharged via either a rigid perforated pipe
or weep holes. Collection pipes should be placed perforations downward near the
bottom of the drainage medium and should discharge in a nonerosive manner away from
foundations, slopes, and other improvements. Drainage medium consisting of a gravel
blanket or permeable material should have a width of approximately 1 foot and should
extend upward to within 1 foot of the top of the wall backfill. The upper foot of backfill
over the drainage medium should consist of native soil to reduce the flow of surface
drainage into the wall drain system. Gravel blankets should be separated from the backfill
soil using a permeable synthetic fabric conforming to Caltrans Standard Specifications,
Section 88-1.0213, Class A. Permeable material should conform to Section 68-2.02F(3),
Class 2, of the Caltrans Standard Specifications. Manufactured synthetic drains such as
Miradrain or Enkadrain should be installed in accordance with the recommendations of
the manufacturer.
4. Retaining walls should be backfilled with either native soil or clean imported granular
material. The backfill material should be placed in thin, moisture conditioned lifts,
compacted in accordance with the recommendation provided in the Site Preparation and
Grading section of this report.
5. Long-term settlement of properly compacted sand or gravel retaining wall backfill should
be assumed to be about X percent of the depth of the backfill. Long-term settlement of
properly compacted clayey retaining wall backfill should be assumed to be about % to 1
percent of the depth of the backfill. Improvements constructed near the tops of retaining
walls should be designed to accommodate the estimated settlement.
6. The architect/engineer should bear in mind that retaining walls bytheir nature are flexible
structures, and the flexibility can often cause cracking in surface coatings. Where walls
are to be plastered or will otherwise have a finish surface applied, this flexibility should
be considered in determining the suitability of the surfacing material, spacing of
horizontal and vertical joints, connections to structures, etc.
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January 24, 2019
Slabs -on -Grade and Exterior Flatwork
1. Interior slabs -on -grade and exterior flatwork should have minimum thicknesses of 4 full
inches and should be reinforced as directed by the architect/engineer. Based on soil
expansion only, interior slab reinforcement should consist of #3 rebar spaced at 24 inches
on center each way. Due to the soil expansion potential, steel reinforcement should also
be provided for exterior flatwork. The subgrade modulus (K30) for slab design should be
60 psi/inch.
2. Interior slabs and foundations should be doweled together as required by the
architect/engineer; based on soil expansion potential only, the dowels should be a
minimum of #3 rebar spaced on 24-inch centers.
3. To help protect interior slabs -on -grade from damage due to expansive soils, they should
be underlain by a minimum of 12 inches of nonexpansive imported material. Prior to
placement of the nonexpansive imported material, the soil on the building pad should be
moisture conditioned to a minimum 3 percent over the soil's optimum moisture content
to a minimum depth of 12 inches. The soil moisture conditioning should be observed
and tested by the geotechnical engineer.
4. In areas where moisture transmitted from the subgrade would be undesirable, a vapor
retarder should be utilized beneath the floor slab. The vapor retarder should comply with
ASTM Standard Specification E 1745-17 and the latest recommendations of ACI
Committee 302. The vapor retarder should be installed in accordance with ASTM
Standard Practice E 1643-18a. Care should be taken to properly lap and seal the vapor
retarder, particularly around utilities, and to protect it from damage during construction.
5. If sand or other permeable material is to be placed over the vapor retarder, the material
over the vapor retarder should be only lightly moistened and not saturated prior to
casting the slab concrete. Recent studies, including those by ACI Committee 302, have
concluded that excess water above the vapor retarder would increase the potential for
moisture damage to floor coverings and could increase the potential for mold growth or
other microbial contamination. The studies also concluded that it is preferable to
eliminate the sand layer and place the slab concrete in direct contact with the vapor
retarder, particularly during wet weather construction. However, placing the concrete
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directly on the vapor retarder would require special attention to using the proper vapor
retarder, concrete mix design, and finishing and curing techniques.
Exterior flatwork should be cast on a minimum 6-inch thick layer of compacted,
nonexpansive material such as clean sand or aggregate base. However, a greater
thickness of nonexpansive material would enhance flatwork performance. Prior to
placement of the nonexpansive material, the soil surface in the flatwork area should be
at or above optimum moisture content, and no desiccation cracks should be present.
Assuming that movement (i.e.,'/-inch or more) of exterior flatwork beyond the structure
is acceptable, the flatwork should be designed to be independent of the building
foundations. The flatwork should not be doweled to foundations, and a separator should
be placed between the two. If differential movement of flatwork is considered
undesirable, the flatwork should be designed and constructed in roughly the same
manner as the structure slabs, and reinforced footings should be provided around the
perimeter of the flatwork.
To reduce shrinkage cracks in concrete, the concrete aggregates should be of appropriate
size and proportion, the water/cement ratio should be low, the concrete should be
properly placed and finished, contraction joints should be installed, and the concrete
should be properly cured. This is particularly applicable to slabs that will be cast directly
upon a vapor retarder and those that will be protected from transmission of vapor by use
of admixtures or surface sealers. Concrete materials, placement and curing specifications
should be at the direction of the architect/engineer.
Utility Trenches
1. A select, noncorrosive, granular, easily compacted material should be used as bedding
and shading immediately around utility pipes. The site soils may be used for trench
backfill above the select material. However, if obtaining compaction is difficult with the
site soils, use of a more easily compacted sand may be desirable. The upper foot of
backfill in unimproved areas should consist of native material to reduce the potential for
seepage of water into the backfill.
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2. Trench backfill in the upper 8 inches of subgrade beneath pavement areas should be
compacted to a minimum of 92 percent of maximum dry density. Trench backfill in other
areas should be compacted to a minimum of 90 percent of maximum dry density. Jetting
of utility trench backfill should not be allowed. For public utilities, the trench backfill and
compaction requirements should be in accordance with the requirements of the City of
Gilroy.
3. Where utility trenches extend under perimeter foundations, exterior flatwork, or
pavement, the trenches should be backfilled entirely with compacted native soil. The
zone of native soil should extend to a minimum distance of 2 feet on both sides of the
foundation, as well as the edges of flatwork or pavement. If utility pipes pass through
sleeves cast into the perimeter foundations, the annulus between the pipes and sleeves
should be sealed.
Pavement Sections
An R-value test of a sample of the upper clayey sand resulted in an R-value of 22. However, the
following pavement sections were based on an R-value of 15 to account for variabilities of the
clay content of the upper soil. The asphalt concrete (AC) sections were designed in accordance
with the Caltrans Highway Design Method for Traffic Indices (TIs) of 4.0 through 7.0.
Determination of the appropriate TI for each area to be paved is the province of the design
engineer and the jurisdiction. For public street improvements, the pavement sections should be
in accordance with the specifications of the City of Gilroy Public Works Department.
R-value
Traffic
AC
Class 2 Base
Index
Thickness
Thickness
15
4.0
2.5"
6"
15
4.5
2.5"
8"
15
5.0
3.0"
8"
15
5.5
3.0"
10"
15
6.0
3.5"
11"
15
6.5
4.0"
12"
15
7.0
4.0"
13"
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Gilroy, California
1. The calculated base and AC thicknesses are for compacted material. Normal Caltrans
construction tolerances should apply. The aggregate base should conform to Caltrans
Class 2.
2. In private driveway and parking areas, the upper 8 inches of subgrade soil should be
compacted to a minimum 92 percent of maximum dry density. The aggregate base
courses should be compacted to a minimum 95 percent of maximum dry density. For
public street improvements, the subgrade and aggregate base should be compacted in
accordance with the specifications of the City of Gilroy.
3. The subgrade and base should be firm and unyielding when proofrolled with heavy,
rubber -tired equipment prior to continuing construction. The subgrade soils should be
periodically moistened as necessary prior to placement of the aggregate base to maintain
the soil moisture content near optimum.
4. To provide stability for curbs, they should be set back a minimum of 3 feet from the tops
of slopes. Foundations may be provided to increase curb stability, particularly atop
slopes.
5. Pavement longevity will be enhanced if the surface grade drains away from the edges of
the pavement. Finished AC surfaces should slope toward drainage facilities at 2 percent
where practicable, but in no case should water be allowed to pond.
6. Cutoff walls below curbs and around landscape islands may be used to extend the life of
the pavement by reducing irrigation water and runoff that seeps into the aggregate base.
Where utilized, cutoff walls should extend through the aggregate base to penetrate a
minimum of 6 inches into the subgrade soils.
7. To reduce migration of surface drainage into the subgrade, maintenance of the paved
areas is critical. Any cracks that develop in the AC should be promptly sealed.
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January 24, 2019
Site Drainage and Finish Improvements
1. Unpaved ground surfaces should be finish graded to direct surface runoff away from site
improvements at a minimum 5 percent grade for a minimum distance of 10 feet. The site
should be similarly sloped to drain away from improvements during construction. If this
is not practicable due to the terrain, property lines, or other site features, swales with
improved surfaces or other drainage facilities should be provided to divert runoff from
those areas. The landscape should be planned and installed to maintain proper surface
drainage conditions.
2. Runoff should discharge in a non -erosive manner away from foundations, pavement,
slopes, and other improvements in accordance with the requirements of the governing
jurisdictions.
3. Stabilization of surface soils, particularly those disturbed during construction, is essential
to protect the site from erosion damage. Care should betaken to establish and maintain
vegetation.
4. Due to the soil expansion potential, open areas adjacent to foundations, exterior flatwork,
and other improvements should be irrigated or otherwise maintained so that constant
moisture conditions are created throughout the year. Irrigation systems should be
controlled to the minimum levels that will sustain the vegetation without saturating the
soil.
Soil Percolation Rate Testing
Three sets of two soil percolation rate tests were performed in borings drilled at the approximate
locations indicated on the attached Boring and Percolation Test Location Map. The percolation
tests were conducted at nominal depths ranging from 3 to 7 feet below the ground surface using
the Shallow Quick Infiltration Testing Methodology, as detailed in the document Native Soil
AssessmentforSmalllnfiltration-BasedStormwaterControl Measures prepared by Earth Systems
Pacific forthe Central Coast Low Impact Initiative (2013). The percolation test borings were cased
with perforated PVC pipe, and the annular spaces were backfilled with gravel. They were then
filled with clear water, and the water level was maintained at existing grade for approximately
30 minutes (i.e. kept at a constant head). From that point on, the tests were conducted as a
302580-001 15 1901-020.SER
percolation test results are attached.
These test results only indicate the percolation rates at the specific locations and under specific
conditions. Sound engineering judgment should be exercised in extrapolating the test results for
other conditions or locations. Technical design references vary in methods they present for using
these types of test results. However, most references include reduction and/or correction factors
for several parameters including, but not limited to, size of the stormwater infiltration system
relative to the test volume, number of tests conducted, variability in the soil profile, anticipated
silt loading, anticipated biological buildup, anticipated long-term maintenance, and other factors.
The designer of the stormwater infiltration system should select the appropriate reduction
and/or correction factors based on these considerations.
It is also pointed out that the measured rates were for undisturbed native soils, and that site
grading, fill placement, and soil compaction can have significant effects on the actual infiltration
rates that will be experienced following construction.
Geotechnical Observation and Testing
1. It must be recognized that the recommendations contained in this report are based on a
limited subsurface investigation and rely on continuity of the subsurface conditions
encountered.
2. It is assumed that Earth Systems Pacific will be retained to provide consultation during
the design phase, to interpret this report during construction, and to provide construction
monitoring in the form of testing and observation.
3. Unless otherwise stated, the terms "compacted" and "recompacted" refer to soils placed
in level lifts not exceeding 8 inches in loose thickness and compacted to a minimum of 90
percent of maximum dry density. The standard tests used to define maximum dry density
and field density should be ASTM D 1557-12 and ASTM D 6938-17, respectively, or other
methods acceptable to the geotechnical engineer and jurisdiction.
302580-001
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Gilroy Nissan Dealership January 24, 2019
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4. Unless otherwise stated, "moisture conditioning" refers to adjusting the soil moisture to
at least optimum moisture prior to application of compactive effort.
5. At a minimum, the following should be provided by the geotechnical engineer:
• Review of grading and foundation plans as they near completion
• Professional observation during site preparation, grading, and foundation
construction
• Oversight of soil compaction testing during grading
• Oversight of soils special inspection during grading
6. Special inspection of grading should be provided as per Sections 1705.6 and 1705.8, and
Tables 1705.6 and 1705.8 of the CBC; the soils special inspector should be under the
direction of the geotechnical engineer in our opinion, the following operations should be
subject to continuous soils special inspection:
• Overexcavation to the recommended depths
• Scarification and recompaction
• Fill placement and compaction
• Foundation pier drilling
7. In our opinion, the following operations may be subject to periodic soils special
inspection; subject to approval by the Building Official:
• Site preparation
• Proposed imported materials
• Building pad moisture conditioning
• Observation of foundation excavations
• Compaction of utility trench backfill
• Compaction of pavement subgrade and aggregate base
8. It will be necessary to develop a program of quality control prior to beginning grading. It
is the responsibility of the owner, contractor, or project manager to determine any
additional inspection items required by the architect/engineer or the governing
jurisdiction.
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Gilroy, California
9. The locations and frequencies of compaction tests should be per the recommendations
of the geotechnical engineer at the time of construction. The recommended test
locations and frequencies may be subject to modification by the geotechnical engineer
based upon soil and moisture conditions encountered, the size and type of equipment
used by the contractor, the general trend of the compaction test results, and other
factors.
10. A preconstruction conference between a representative of the owner, the geotechnical
engineer, the soils special inspector, the architect/engineer, and contractors is
recommended to discuss planned construction procedures and quality control
requirements. The geotechnical engineer should be notified at least 48 hours prior to
beginning grading operations.
Closure
This report is valid for conditions as they exist at this time for the type of project described herein.
Our intent was to perform the investigation in a manner consistent with the level of care and skill
ordinarily exercised by members of the profession currently practicing in the locality of this
project under similar conditions. No representation, warranty, or guarantee is either expressed
or implied. This report is intended for the exclusive use by the client as discussed in the Scope of
Services section. Application beyond the stated intent is strictly at the user's risk.
If changes with respect to the project type or location become necessary, if items not addressed
in this report are incorporated into plans, or if any of the assumptions stated herein are not
correct, the geotechnical engineer should be notified for modifications to this report. Any items
not specifically addressed in this report shall comply with the current edition of the California
Building Code and the requirements of the governing jurisdiction.
The preliminary recommendations of this report are based upon the geotechnical conditions
encountered during the investigation and may be augmented by additional requirements of the
architect/engineer, or by additional recommendations provided by the geotechnical engineer
based on conditions exposed at the time of construction.
302580-001 18 1901-020.SER
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Gilroy, California
If Earth Systems Pacific is not retained to provide construction observation and testing services,
it shall not be responsible for the interpretation of the information by others or any
consequences arising there from.
This document, the data, conclusions, and recommendations contained herein are the property
of Earth Systems Pacific. This report shall be used in its entirety, with no individual sections
reproduced or used out of context. Copies may be made only by Earth Systems Pacific, the client,
and his authorized agents for use exclusively on the subject project. Any other use is subject to
federal copyright laws and the written approval of Earth Systems Pacific.
Thank you for this opportunity to have been of service. Please do not hesitate to contact this
office if you have any questions regarding this report.
Sincerely,
Earth
Geotechnical Engineer
Attachments: Boring and Percolation Test Location Map
Boring Logs (8)
Laboratory Test Results
Percolation Test Results
Doc. No.: 1901-020.SER/ev
Kira 90rtiz
Project Engineer
302580-001 19 1901-020.SER
MA P-113
A
B
B8 LEO
B7 ftbi'
4 lip=
2
B
F -C—MMI
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M A
P-3A P-313
P-2A P-2B
4L B8 Approximate boring location
7 , , P-313 Approximate Percolation test location
U
k
Base: SCOTT & Associates (2018)
Gilroy Nissan Dealership Boring and Percolation Test Location Map
Earth Systems Pacific Chestnut Street APNS, 841-74-002,003, and 004
aaGilroy, California 302580-001
Earth Systems Pacific
LOGGED BY: D. Teimoorian
DRILL RIG: Simco 2400 SK-1
AUGER TYPE: 6" Solid Stem
Boring No. 1
PAGE 1 OF 1
FILE NO.: 302580-001
DATE: 9/27/2018
Gilroy Nissan Dealership
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5
3.5-5.0
1-3
95.9
15.0
6
6
7
a
-few fine gravel
g
5
8
SC
CLAYEY SAND with GRAVEL; dense, brown, moist,
10
8.5-10.0
1-4
23
-
, ;
mostly fine gravel, fine to coarse sand
11
9.5-13.0
Bag B
0
12
13
_
SC
;^
_—____ — _ _ _--_—_
CLAYEY SAND; medium dense, dark yellow brown,
-
moist, fine to coarse sand
10
14
8
*
13.5-15.0
1-5
14
15
16
17
16
-
-dense
15
19
_
21
20
18.5-20.0
1-6
•
22
Bottom of boring at 20'
-
21
Groundwater not encountered
22
23
24
25
26
LEGEND: = 2.5" Mod Cal Sample O Bulk Sample p Shelby Tube 0 SPT 1 Groundwater
NOTE: This log of subsurface conditions is a simplification of actual conditions encountered. it applies at the location and time of drilling.
Subsurface conditions may differ at other locations and times.
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/\ Earth Systems Pacific
1i
LOGGED BY: D. Teimoorian
DRILL RIG: Simco 2400 SK-1
AUGER TYPE: 6" Solid Stem
Boring No. 3
PAGE 1 OF 1
FILE NO.: 302580-001
DATE: 9/27/2018
SAMPLE
DATA
w
Gilroy Nissan Dealership
w
W
x
g
o
Chestnut Street., APNs 841-74-002, 003, and 004
u,
Gilroy,
Q v
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a
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aa
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SANDY LEAN CLAY; medium stiff, dark brown, moist,
slightly cemented
1
4
z
4
-
1.5-3.0
3-1
=
107.2
15.1
5
4.25
3
4
-stiff, very moist
3
3-2
97.5
20.4
4
3.25
SC
�;,
CLAYEY SAND; loose to medium dense, dark yellow
5
3.5-5.0
3-3
=
10
_
brown, moist, fine to medium sand, few fine gravel
6
7
a
.
-very moist
s
S
1
CL
LEAN CLAY; very stiff, dark yellow brown, moist, few
10
fine sand
8.5-10.0
3-4
16
n
12
_
SC
- R
CLAYEY SAND; dense, dark yellow brown, moist, fine to
'=
coarse sand, few fine gravel
13
1ti
a
12
15
13.5-15.0
3-5
•
22
15
Bottom of boring at 15'
-
16
Groundwater not encountered
17
16
19
20
21
22
23
24
25
26
LEGEND: = 2.5" Mod Cal Sample O Bulk Sample 0 Shelby Tube 0 SPT t Groundwater
NOTE: This log of subsurface conditions Is a simplification of actual conditions encountered. It applies' at the location and time of drilling.
Subsurface conditions may differ at other locations and times.
Earth Systems Pacific
LOGGED BY: D. Teimoorian
DRILL RIG: Simco 2400 SK-1
AUGER TYPE: 6" Solid Stem
Boring No. 4
PAGE 1OF1
FILE NO.: 302580-001
DATE: 9/27/2018
SAMPLE DATA
Gilroy Nissan Dealership
_
w
w
g
o
Chestnut Street., APNs 841-74-002, 00% and 004
w ,0
�
Gilroy, California
> �
a m
a nw.
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Q
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EL
a
-
CL
NSANDY
LEAN CLAY; medium stiff, dark brown, slightly
moist, fine sand, slightly cemented
1
6
2
-moist, not cemented
6
1.5-3.0
4-1
105.4
9.5
6
4.00
3
4
-brown
4
-
3
5
3.5-5.0
4-2
5
3.25
s
7
8
-very moist
5
1.00
9
4-3
15
8.5-10.0
4-4
20
SC
;_;
CLAYEY SAND with GRAVEL; dense, dark yellow brown,
10
moist, fine to coarse sand, fine to coarse gravel
•�
.ii
12
r
13
i ..
-medium dense
18
14
,'_
._.�:
15
13.5-15.0
4-5
•
13
15
Bottom of boring at 15'
-
16
Groundwater not encountered
17
18
19
20
21
22
23
24
25
2s
LEGEND: = 2.5" Mod Cal Sample O Bulk Sample p Shelby Tube 0 SPT Z Groundwater
NOTE: This log of subsurface conditions is a simplification of actual conditions encountered. It applies at the location and time of drilling.
Subsurface conditions may differ at other locations and times.
Earth Systems Pacific
LOGGED BY: D. Teimoorian
DRILL RIG: Simco 2400 SK-1
AUGER TYPE: 6" Solid Stem
Boring No. 5
PAGE 1 OF 1
FILE NO.: 302580-001
DATE: 9/2712018
N
Gilroy Nissan Dealership
SAMPLE DATA
w
w
_
5
d
Chestnut Street., APNs 841-74-002, 003, and 004
w w
y
Gilroy, California
a' m
c.. asy
W ^�
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N
N
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•
CLAYEY SAND; medium dense, dark brown, moist, fine
'*:;
sand, cemented
I
Y.�
9
2
-not cemented, brown
9
1.5-3.0
5-1
=
93.9
9.0
11
3
1.0-5.0
Bag C
O
s
_
4
5
5
-;
[LL=36, 13I=20)
3.5-5.0
5-2
102.5
10.5
7
6
7
6
_
-dark yellow brown, fine to coarse sand, few fine gravel
9
-
10
l0
8.5-10.0
5-3
1]
11
a,
12
13
13
14
14
13.5-15.0
5-4
ld
15
16
. 4
17
Is
-
-fine to coarse gravel
10
19
15
20
18.5-20.0
5-5
•
15
Bottom of boring at 20'
-
21
Groundwater not encountered
22
23
24
25
26
LEGEND: = 2.5" Mod Cal Sample O Bulk Sample O Shelby Tube 0 SPT T. Groundwater
NOTE: This log of subsurface conditions Is a simplification of actual conditions encountered. It applles of the location and time of drilling.
Subsurface conditions may differ at other locations and times.
DEPTH
(feet)
0
USCS CLASS
�1
�!:
'.��: -I' '.
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SYMBOL
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Earth Systems Pacific
LOGGED BY: D. Teimoorian
DRILL RIG: Simco 2400 SK-1
AUGER TYPE: 6" Solid Stem
Boring No. 7
PAGE 1 OF 1
FILE NO.: 302580-001
DATE: 9/27/2018
N
Gilroy Nissan Dealership
SAMPLE DATA
_
w
z
uj
g
J
o
Chestnut Street.APNs 841-74-002, 003, and 004
oGilroy,
L)
Co,
California
ii W.
a
wCL
o
w N
�oo� o��c�Qop�ooa
z
�z
N
ma
o
o
a
_
CL
SANDY LEAN CLAY; medium stiff, dark brown, slightly
moist, fine sand, cemented
1
_
7
2
-moist
7
[Compressive Strength:19 psi (2,664 psf)]
1.5-3.0
7-1
101.3
11.1
8
3
_
-not cemented, medium stiff, dark yellow brown
4
4
_
4
5
3.5-5.0
7-2
106.7
13.9
6
6
7
a
_
CL
LEAN CLAY; very stiff, dark yellow brown, moist
9
8
9
8.5-10.0
7-3
20
10
11
SC
CLAYEY SAND; medium dense, yellow brown, moist,
12
; .
fine to coarse sand, few fine gravel
13
15
14
'
15
`
13.5-15.0
7-4
•
15
15
Bottom of boring at 15'
-
16
Groundwater not encountered
17
18
19
20
21
22
23
24
25
26
LEGEND: = 2.5" Mod Cal Sample Q Bulk Sample p Shelby Tube 9 SPT Z Groundwater
NOTE: This log of subsurface conditions is a simplification of actual conditions encountered. It applies at the location and time of drilling.
Subsurface conditions may differ at other locations and times.
Earth Systems Pacific
LOGGED BY: D. Teimoorian
DRILL RIG: Simco 2400 SK-1
AUGER TYPE: 6" Solid Stem
Boring No. 8
PAGE 1 OF 1
FILE NO.: 302580-001
DATE: 9/27/2018
SAMPLE DATA
U)
Gilroy Nissan Dealership
r
w
W
_
5
d
Chestnut Street., APNs 841-74-002, 003, and 004
w v
y
Gilroy, California
0
a. m
a a}
w
w
Ov
1n
oc
Q7
QF
n
co
O W
Y�
22 f1 rr��
FW-�
1n Z
Co
o
Co a
a
a
_
CL
N
SANDY LEAN CLAY; stiff, dark brown, moist, fine sand,
slightly cemented
1
2
10
10
-dark yellow brown, not cemented
1.5-3.0
8-1
100.4
10.6
8
3
4
4
6
5
3.5-5.0
8-2
99.9
12.0
6
6
7
6
SC
CLAYEY SAND; medium dense, dark yellow brown,
moist, fine to coarse sand
9
9
n
9
8.5-10.0
8-3
7
10
11
c
12
13
-dense
18
14
26
'"s'•
13.5-15.0
8-4
•
21
is
Bottom of boring at 15'
-
16
Groundwater not encountered
17
to
1a
20
21
22
23
24
25
26
LEGEND: = 2.5" Mod Cal Sample O Bulk Sample O Shelby Tube 0 SPT t Groundwater
NOTE: This log of subsurface conditions is a simplification of actual conditions encountered. It applies at the location and time of drilling.
Subsurface conditions may differ at other locations and times.
0
Gilroy Nissan Dealership File No. 302580-001
Gilroy, California
BULK DENSITY TEST RESULTS
ASTM D 2937-17 (modified for ring liners)
October 5, 2018
BORING
DEPTH
MOISTURE
WET
DRY
NO.
feet
CONTENT, %
DENSITY, pcf
DENSITY, pcf
B-1
2.5 - 3.0
9.9
112.1
101.9
B-1
4.5 - 5.0
15.0
110.3
95.9
B-2
2.5 - 3.0
9.9
112.9
102.8
B-2
4.5 - 5.0
15.3
125.7
109.0
B-3
2.5 - 3.0
15.1
123.4
107.2
B-3
4.0 - 4.5
20.4
117.5
97.5
B-4
2.5 - 3.0
9.5
115.4
105.4
B-5
2.5 - 3.0
9.0
102.3
93.9
B-5
4.5 - 5.0
10.5
113.3
102.5
B-6
8.5 - 9.0
8.8
---
--
B-7
2.5 - 3.0
11.7
113.2
101.3
B-7
4.5 - 5.0
13.9
121.6
106.7
B-8
2.5 - 3.0
10.6
111.0
100.4
B-8
4.5 - 5.0
12.0
111.8
99.9
0 %-k
TINWOM
Gilroy Nissan Dealership
Gilroy, California
File No. 3O2SD0-001
PARTICLE SIZE ANALYSIS mSTMo4zz'63/07o114n17
Boring #5,Bag C @1.0'5.O' October 5,2o18
Clayey Sand (3C)
Sieve size
%Retained
%Pasin
3"(75'mnn)
0
100
2"(50'mnn)
0
100
1.5"(37.5-mm)
O
100
1"(25-mnn)
0
100
3/4"(19-num)
0
100
1/2"(12.5'mm)
0
100
3/8"(9.5',nm)
0
100
#4(4.75-mm)
0
100
48(236'mm)
0
100
A16(1.18-nm)
l
99
#30(000'pm)
l
98
#50(300-pm)
lZ
88
#100(150'pm)
37
63
A200(75'pm)
53
47
oil ME
MCC
allow
0
Gilroy Nissan Dealership
Gilroy, California
File No. 302580-001
PARTICLE SIZE ANALYSIS ASTM D 422-63/07; D 1140-17
Boring #6 @ 4.5 - 5.0' October 5, 2018
Well Graded Sand with Clay and Gravel (SW -SC)
Cu = 27.9; Cc = 1.0
Sieve size
% Retained
% Passing
3" (75-mm)
0
100
2" (50-mm)
0
100
1.5" (37.5-mm)
0
100
1" (25-mm)
0
100
3/4"(19-mm)
0
100
1/2" (12.5-mm)
4
96
3/8" (9.5-mm)
9
91
#4 (4.75-mm)
32
68
#8 (2.36-mm)
50
50
#16 (1.18-mm)
62
38
#30(600-µm)
72
28
#50(300-µm)
86
14
#100(150-µm)
89
11
#200 (75-µm)
92
8
U. S. STANDARD SIEVE OPENING IN INCHES U. S. STANDARD SIEVE NUMBERS
3 2 1.5 1 3/4 12 319 4 R 16 30
100
90
80
V 70
z
N
60
d
p 50
z
Z
U 40
C4
PW. 30
20
10
0
100
10
50 10D 2M
1 0.1
GRAIN SIZE, mm
0.01
Gilroy Nissan Dealership
Gilroy, California
File No. 302580-001
PLASTICITY INDEX ASTM D 4318-17
Clayey Sand (SC) October 5, 2018
Test No.:
1
2
3
4
5
Boring No.:
5, Bag C
Sample Depth:
1.0 - 5.0'
Liquid Limit:
36
Plastic Limit:
16
Plasticity Index:
20
60
50
40
c
Z 30
U
C
L'. 20
0
0
Plasticity Chart
a
CHcrOH
/
/
M
i or O
ML or
L
10 20 30 40 .50 60 70 80 90 t00
Liquid Limit
Gilroy Nissan Dealership
Gilroy, California
File No. 302580-001
PLASTICITY INDEX ASTM D4318-17
Well Graded Sand with Clay and Gravel (SW -SC) October5, 2018
Test No.:
1
2
3
4
5
Boring No.:
6
Sample Depth:
4.5 - 5.0'
Liquid Limit:
0
Plastic Limit:
0
Plasticity Index:
Non -Plastic
60
50
40
U
C
y+ 30
Z
Pr 20
10
0
0
Plasticity Chart
h
Zee
CH
k OH
^f -
M
-I Or 01-
loor
ML or
. L
10 20 30 40 50 60
Liquid Limit
70 80 90 100
Gilroy Nissan Dealership
Gilroy, California
UNCONFINED COMPRESSION ON COHESIVE SOIL
Boring #1 @ 1.5 - 2'
Sandy Lean Clay (CL)
Ring Sample
COMPRESSIVE STRENGTH: 59 psi (8,530 psf)
File No. 302580-001
ASTM D 2166-16
October 5, 2018
Dry Density: 100.3 pcf
Moisture Content: 9.7%
Degree Saturation: 39.6%
Specific Gravity: 2.65 (assumed)
H/D Ratio: 2.51
TIME
(MINUTES)
DEFORM, in
(X 1000)
AXIAL
STRAIN
AREA
(SQ. IN.)
APPLIED
LOAD (LBS)
STRENGTH
(PSI)
STRENGTH
(PSF)
0.5
20
0.0033
4.54
12.6
3
400
1.0
40
0.0066
4.55
39.9
9
1,262
1.5
60
0.0100
4.57
105
23
3,309
2.0
80
0.0133
4.58
140.7
31
4,419
2.5
100
0.0166
4.60
176.4
38
5,522
3.0
120
0.0199
4.62
1 218.4
47
6,813
3.5
140
0.0233
4.63
241.5
52
7,508
4.0
160
0.0266
4.65
254.1
55
7,873
4.5
180
0.0299
4.66
275.1
59
8,495
5.0
200
0.0332
4.68
277.2
59
8,530
5.5
220
0.0365
4.70
239.4
51
7,342
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
10.0
10.5
11.0
11.5
12.0
12.5
13.0
13.5
14.0
14.5
Y•���
Gilroy Nissan Dealership
Gilroy, California
File No. 302580-001
UNCONFINED COMPRESSION ON COHESIVE SOIL ASTM D 2166-16
October 5, 2018
Boring #7 @ 2.5 - 3' Dry Density: 101.3 pcf
Sandy Lean Clay (CL) Moisture Content: 11.1%
Ring Sample Degree Saturation: 46.5%
COMPRESSIVE STRENGTH: 19 psi (2,664 psf) Specific Gravity: 2.65 (assumed)
H/D Ratio: 2.52
TIME
(MINUTES)
DEFORM, in
( X 1000)
AXIAL
STRAIN
AREA
(SQ. IN.)
APPLIED
LOAD (LBS)
STRENGTH
(PSI)
STRENGTH
(PSF)
0.5
20
0.0033
4.46
16.8
4
542
1.0
40
0.0067
4.48
29.4
7
945
1.5
60
0.0100
4.49
48.3
11
1,548
2.0
80
0.0134
4.51
65.1
14
2,079
2.5
100
0.0167
4.52
75.6
17
2,406
3.0
120
0.0200
4.54
84
19
2,664
3.5
140
0.0234
4.56
73.5
16
2,323
4.0
160
0.0267
4.57
48.3
11
1,522
4.5
180
0.0301
4.59
39.9
9
1,253
5.0
200
0.0334
4.60
37.8
8
1,183
5.5
220
0.0367
4.62
37.8
8
1,179
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
10.0
10.5
11.0
11.5
12.0
12.5
13.0
13.5
14.0
14.5
F17
Gilroy Nissan Dealership
Gilroy, California
File No. 302580-001
CONSOLIDATION TEST ASTM D 2435/D2435M-11
October 18, 2018
Boring #4 @ 2.5 - 3' DRY DENSITY: 104.9 pcf
Clayey Sand (SC) MOISTURE CONTENT: 9.5%
Ring Sample SPECIFIC GRAVITY: 2.65 (assumed)
INITIAL VOID RATIO:0.578
0.700
0.650
0.600
V
O
I
D
0.550
R
A
T
1 0.500
O
0.450
0.400 --
0.1
VOID RATIO vs. NORMAL PRESSURE DIAGRAM
10
VERTICAL EFFECTIVE STRESS, ksf
100
Gilroy Nissan Dealership
Gilroy, California
File No. 302580-001
RESISTANCE'R' VALUE AND EXPANSION PRESSURE ASTM D 2844/D2844M-13
October 18, 2018
Boring#1 @ 0.0-5.0' Dry Density @ 300 psi Exudation Pressure: 117.4-pcf
Clayey Sand (SC) %Moisture @ 300 psi Exudation Pressure: 15.5%
Specified Traffic Index: 5.0 R-Value - Exudation Pressure: 30
EXUDATION PR
CHART
90
80
70
60
W 50
Q
40
30
20
10
o ;� =1 I pm l l 1 .. LIB' —.I, I I
800 700 600 500 400 300 200 100 0
EXUDATION PRESSURE, psi
2.0
1.8
C
0.2
R-Value - Expansion Pressure: 22
R-Value @ Equilibrium: 22
EXPANSION PRESSURE CHART
... ... ..EMER Oman 0.000 NKOMO ...................M...
0.0 0.2 0I. 0,6 is 1.0 1.2 1.4 1.6 1.8I
Project: Gilroy Nissan Dealership
PERCOLATION TEST RESULTS
PERCOLATION TEST: P-1A
DATE DRILLED: 9/27/18
DATE TESTED: 10/3/18
TECHNICIAN: RM
CONSTANT HEAD DATA
Time of Constant Head: 30 minutes
Volume Added During Constant Head: 0.7 cubic feet
FALLING HEAD DATA
Project No. 302580-001
PIPE DIAMETER: 3 in
TEST HOLE DIAMETER: 6 in
TEST HOLE DEPTH: 3.2 feet
RISER HEIGHT: 0.28 feet
TEST DURATION: 2 hours
Reference of Measurement: Top of Riser
INTERVAL
(Minutes)
READING
(Feet)
INCREMENTAL
FALL
(Feet)
INFILTRATION
RATE
(Minutes / Inch)
INFILTRATION
RATE
(inches/ Hour)
Constant Head
0.28
---
---
---
30
0.88
0.60
4.2
14
30
1.08
0.20
12.5
4.8
30
1.15
0.07
35.7
1.7
30
1.20
0.05
50.0
1.2
Project: Gilroy Nissan Dealership
PERCOLATION TEST RESULTS
PERCOLATION TEST: P-16
DATE DRILLED: 9/27/18
DATE TESTED: 10/3/18
TECHNICIAN: RM
CONSTANT HEAD DATA
Time of Constant Head: 30 minutes
Volume Added During Constant Head: 1.5 cubic feet
FALLING HEAD DATA
Project No. 302580-001
PIPE DIAMETER: 3 in
TEST HOLE DIAMETER: 6 in
TEST HOLE DEPTH: 7.1 feet
RISER HEIGHT: 1.05 feet
TEST DURATION: 2 hours
Reference of Measurement: Top of Riser
INTERVAL
(Minutes)
READING
(Feet)
INCREMENTAL
FALL
(Feet)
INFILTRATION
RATE
(Minutes / Inch)
INFILTRATION
RATE
(inches/ Hour)
Constant Head
1.05
---
---
---
30
2.21
1.16
2.2
27
30
3.01
0.80
3.1
19
30
3.42
0.41
6.1
10
30
3.69
0.27
9.3
6.5
Project: Gilroy Nissan Dealership Project No. 302580-001
PERCOLATION TEST RESULTS
PERCOLATION TEST: P-2A PIPE DIAMETER: 3 in
DATE DRILLED: 9/27/18
DATE TESTED: 10/3/18
TECHNICIAN: RM
CONSTANT HEAD DATA
Time of Constant Head: 30 minutes
Volume Added During Constant Head: 2.9 cubic feet
FALLING HEAD DATA
TEST HOLE DIAMETER: 6 in
TEST HOLE DEPTH: 6.8 feet
RISER HEIGHT: 0.86 feet
TEST DURATION: 2 hours
Reference of Measurement: Top of Riser
INTERVAL
(Minutes)
READING
(Feet)
INCREMENTAL
FALL
(Feet)
INFILTRATION
RATE
(Minutes / Inch)
INFILTRATION
RATE
(Inches / Hour)
Constant Head
0.86
---
---
---
30
2.25
1.39
1.8
33
30
3.11
0.86
2.9
21
30
3.78
0.67
3.7
16
30
4.20
0.42
6.0
10
7(*
Project: Gilroy Nissan Dealership
PERCOLATION TEST RESULTS
PERCOLATION TEST: P-213
DATE DRILLED: 9/27/18
DATE TESTED: 10/3/18
TECHNICIAN: RM
CONSTANT HEAD DATA
Time of Constant Head: 30 minutes
Volume Added During Constant Head: 0.9 cubic feet
FALLING HEAD DATA
Project No. 302580-001
PIPE DIAMETER: 3 in
TEST HOLE DIAMETER: 6 in
TEST HOLE DEPTH: 3.2 feet
RISER HEIGHT: 0.36 feet
TEST DURATION: 2 hours
Reference of Measurement: Top of Riser
INTERVAL
(Minutes)
READING
(Feet)
INCREMENTAL
FALL
(Feet)
INFILTRATION
RATE
(Minutes / Inch)
INFILTRATION
RATE
(inches/ Hour)
Constant Head
0.36
---
---
---
30
0.92
0.56
4.5
13
30
1.22
0.30
8.3
7.2
30
1.33
0.11
22.7
2.6
30
1.40
0.07
35.7
1.7
Project: Gilroy Nissan Dealership Project No. 302580-001
PERCOLATION TEST RESULTS
PERCOLATION TEST: P-3A PIPE DIAMETER: 3 in
DATE DRILLED: 9/27/18
DATE TESTED: 10/3/18
uf$.'Ii1C41TWO A 1101 ►Ti1
CONSTANT HEAD DATA
Time of Constant Head: 30 minutes
Volume Added During Constant Head: 3.3 cubic feet
FALLING HEAD DATA
TEST HOLE DIAMETER: 6 in
TEST HOLE DEPTH: 6.6 feet
RISER HEIGHT: 1.03 feet
TEST DURATION: 2 hours
Reference of Measurement: Top of Riser
INTERVAL
(Minutes)
READING
(Feet)
INCREMENTAL
FALL
(Feet)
INFILTRATION
RATE
(Minutes / Inch)
INFILTRATION
RATE
(inches/ Hour)
Constant Head
1.05
---
---
---
30
2.33
1.28
2.0
30
30
2.89
0.56
4.5
13
30
3.19
0.30
8.3
7.2
30
3.42
0.23
10.9
5.5
Project: Gilroy Nissan Dealership
PERCOLATION TEST RESULTS
PERCOLATION TEST: P-3B
DATE DRILLED: 9/27/18
DATE TESTED: 10/3/18
TECHNICIAN: RM
CONSTANT HEAD DATA
Time of Constant Head: 30 minutes
Volume Added During Constant Head: 0.9 cubic feet
FALLING HEAD DATA
Project No. 302580-001
PIPE DIAMETER: 3 in
TEST HOLE DIAMETER: 6 in
TEST HOLE DEPTH: 3.3 feet
RISER HEIGHT: 0.51 feet
TEST DURATION: 2 hours
Reference of Measurement: Top of Riser
INTERVAL
(Minutes)
READING
(Feet)
INCREMENTAL
FALL
(Feet)
INFILTRATION
RATE
(Minutes / Inch)
INFILTRATION
RATE
(inches/ Hour)
Constant Head
0.51
---
---
---
30
0.90
0.39
6.4
9.4
30
1.11
0.21
11.9
5.0
30
1.21
0.10
25.0
2.4
30
1.27
0.06
41.7
1.4