Agenda Item # 6.1 - Benjamin Hwang, P.E., Valley Water | Received 12/04/20231
Cindy McCormick
From:Benjamin Hwang <BHwang@valleywater.org>
Sent:Thursday, December 7, 2023 3:26 PM
To:Cindy McCormick; Rita Khosla
Cc:Yvonne Arroyo; Vanessa De La Piedra; Geoffrey Tick; Jeannine Larabee
Subject:RE: EXTERNAL - Initial Study/Mitigated Negative Declaration for Storquest Self-Storage
(1000 Gilman Avenue) (West Branch Llagas Creek)
Thank you, Cindy. The revisions adequately address Valley Water’s comments.
BENJAMIN HWANG, P.E.
ASSOCIATE ENGINEER - CIVIL
Community Projects Review Unit
Watershed Stewardship and Planning Division
bhwang@valleywater.org
Tel. (408) 630-3066 | Cell. (408) 510-0768
SANTA CLARA VALLEY WATER DISTRICT
5750 Almaden Expressway, San Jose CA 95118
www.valleywater.org
Clean Water . Healthy Environment . Flood Protection
From: Cindy McCormick <Cindy.McCormick@ci.gilroy.ca.us>
Sent: Thursday, December 07, 2023 12:42 PM
To: Rita Khosla <RKhosla@valleywater.org>
Cc: Yvonne Arroyo <yarroyo@valleywater.org>; Benjamin Hwang <BHwang@valleywater.org>; Vanessa De La Piedra
<vdelapiedra@valleywater.org>; Geoffrey Tick <GTick@valleywater.org>; Jeannine Larabee <JLarabee@valleywater.org>
Subject: RE: EXTERNAL - Initial Study/Mitigated Negative Declaration for Storquest Self-Storage (1000 Gilman Avenue)
(West Branch Llagas Creek)
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Hi Rita and Ben –
Please see attached highlighted edits to the IS/MND in response to your comment letter. I’ve also summarized our
response below.
Response 1: Staff has corrected the typo and changed the reference from Ronan Channel / Miller Slough to
“West Branch Llagas Creek / Miller Slough” on page 54 of the IS/MND.
Response 2: City staff conferred with the applicant, Public Works staff, and with the City’s environmental
consultant. As stated on page 2 of the IS/MND, the two bioretention ponds and a stormwater basin were
designed and sized to meet the requirements outlined in the Stormwater Management Guidance Manual for
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Low Impact Development and Post Construction Requirements for the City of Gilroy, Morgan Hill and County
of Santa Clara (2015) and the Santa Clara County Drainage Manual (2007). The project also includes source
control best management practices (BMPs) to minimize the introduction of pollutants to the drain system.
Further, the project would be required to comply with the City’s Municipal Code, including Chapter 27C.25,
Water Pollution Control, which requires preparation and implementation of a Water Pollution Control Drawing
and Erosion Control Plan. Accordingly, the project would implement the minimum standards and specifications
of the California Stormwater Quality Association BMPs during construction.
Furthermore, there are several conditions of approval regarding stormwater and storm drain protection and
maintenance (#65, 72, 73, 83, 90, 93, 94, 95, 101, 113, 114, 115, 116, 117, 119, 123, and 138.
The following was added to the Hydrology and Water Quality section operation discussion on page 56 of the
IS/MND, as highlighted in the attached excerpt. The intent of the bioretention pond is for runoff water quality,
flow-duration control (hydromodification management), and peak flow control. The Stormwater Control Plan is
designed to treat the runoff from the project with bioretention. The bioretention ponds are not lined, but
infiltration is not the intent of the ponds, and water that filters through the biotreatment soil mix is considered
treated. Runoff that exceeds the capacity of the bioretention ponds is routed into the detention pond. The
detention pond is designed to release water into the existing swale through a flow metering structure to
maintain pre-development flow rates.
The following discussion was added to the Hydrology and Water Quality section, reference “b”, of the IS/MND
page 56/57, as highlighted in the attached excerpt. “However, the low permeability of onsite soils have low
infiltration rates which limits the opportunity to infiltrate stormwater on-site even in the pre project condition.
Thus, the site is likely not a location of significant groundwater recharge in the pre-project conditions.
Therefore, impacts to groundwater from the addition of impervious areas would be less than significant .”
Response 3: Page 58 of the IS/MND has been corrected, as illustrated in the attached and highlighted
excerpt.
Response 4: The sentence “the project site is subject to water surface elevations approximately between
188.2-ft (NAVD 88) and 189.3 (NAVD 88) during the 100-year flood or 1% annual exceedance event .” was
added to page 58 of the IS/MND. The phrase “where flood depths are minimal” was removed from the end of
the highlighted sentence on page 58 of the IS/MND.
Response 5: Page 59 of the IS/MND was updated to reflect the revised date of the document.
From: Rita Khosla <RKhosla@valleywater.org>
Sent: Monday, December 4, 2023 5:38 PM
To: Cindy McCormick <Cindy.McCormick@ci.gilroy.ca.us>
Cc: Yvonne Arroyo <yarroyo@valleywater.org>; Benjamin Hwang <BHwang@valleywater.org>; Vanessa De La Piedra
<vdelapiedra@valleywater.org>; Geoffrey Tick <GTick@valleywater.org>; Jeannine Larabee <JLarabee@valleywater.org>
Subject: EXTERNAL - Initial Study/Mitigated Negative Declaration for Storquest Self-Storage (1000 Gilman Avenue) (West
Branch Llagas Creek)
Thank you,
Rita Khosla
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Staff Analyst
Community Projects Review Unit
rkhosla@valleywater.org
Tel. (408) 630-2072