April 25, 2025
Santa Clara Valley Water District
Attention: DLGI Draft EIR Comments
5750 Almaden Expressway
San Jose, CA 95118
Via email to: DLGI@valleywater.org
Re: Sierra Club Comments on Design Level Geotechnical Investigations for the Pacheco Reservoir Expansion Project Public Draft Environmental Impact Report
The Sierra Club appreciates the opportunity to evaluate the Design Level Geotechnical Investigations for the Pacheco Reservoir Expansion Project Public Draft Environmental Impact Report (EIR). Our comments are detailed below. We also support the comments submitted by Soluri Meserve law corporation and comments from the Santa Clara Valley Bird Alliance.
Number of Helicopter and Surface Vehicle Trips
The number of surface vehicle trips along the various access routes is unclear. The EIR states that “the Proposed Project would result in a total of approximately 16 daily round trips (32 individual daily trips)” (page 3-44) but does not explain the purpose of these trips. We assume this is just trips entering and leaving the site and does not include internal trips. This needs to be clarified.
Regarding access roads, the EIR states there will be one or two trips per day (page 3-99). Regarding helicopter-access borings, the EIR states “it would take nine to 12 helicopter trips to transport platform materials and equipment back and forth initially ... to an activity site” and a “similar number of helicopter trips ... for removal” (page 2-36). However, other information in the EIR indicates that there will be many more trips due to the amount of materials, equipment and personnel needed for all activities as identified below. The number of trips cited above and in Table 2-5 should be updated accordingly and additional equipment should be added to this table.
Materials and Equipment
Porta-potties
Shade structures
Generators
Laboratory testing equipment for onsite testing of cores
Supplies to store boring samples
Boring samples removed for offsite storage
Drill fluid wastes to be removed
Tremie pipes
Equipment and materials to backfill and seal borings
Erosion control supplies such as straw bales (wattles), silt fences, sandbags, erosion control blankets, and geotextiles or plastic covers.
Water trucks sufficient to implement air quality dust control measures (should precede all vehicles accessing drilling sites on unpaved access routes)
Personnel
Biologists, botanists, arborists to evaluate sites and oversee activities prior to, during, and after investigation activities
Soils engineer or engineering geologist to direct backfill per County Grading Ordinance (see page 3-208)
Laborers to do manual handwork: hammering; vegetation clearing; and hand contouring, leveling, and backfilling at helicopter sites
All of these trips need to be accounted for in relation to impacts on biological resources, air quality, greenhouse gas emissions, and energy.
Personnel Access to Helicopter Sites
The EIR should describe how personnel will reach helicopter-access drilling sites and analyze the impacts related to that method of access. If personnel will also be transported by helicopter, please increase the number of helicopter trips and update analysis accordingly. If personnel will travel over land to helicopter-access drilling sites, please describe how that access will occur and discuss/analyze any associated impacts, particularly any potential impacts to biological resources and how those impacts will be mitigated.
Risk of Erosion on Steep Access Routes
The information in Table 2-4. Proposed Existing Access Roads and Temporary Access Routes and Staging Areas is not sufficient to understand the risks of erosion related to travel on unimproved access routes, stating only that the mean slope is 13%. This is not sufficient information about the slope of off-road access routes. The number and length of routes with slope greater than 20% needs to be identified and the impact of implementing VHP AMM-93 needs to be discussed.
VHP AMM-93. When accessing upland areas adjacent to riparian areas or streams, access routes on slopes of greater than 20% should generally be avoided. Subsequent to access, any sloped area should be examined for evidence of instability and either revegetated or filled as necessary to prevent future landslide or erosion.
As specified in our scoping comments, we request that the project description include a section about the access routes shown in yellow on Figures 2.2a through 2.2e. Additional information is needed to evaluate impacts on plants and wildlife, soil, water quality (erosion), etc. The information should include a table describing each access segment that includes the following: length of the segment; quality and width of current surface (or indicate undisturbed); maximum slope; stream-bed crossings; vegetation types (including any natural communities); and BMPs to be applied. Accumulated impacts from all the segments should also be evaluated in the appropriate environmental impact categories.
Water Use and Water Supply
Given the need for dust control on unpaved roads and access routes discussed above, more than 2000 gallons per day will be needed for water trucks. Please update Table 2-5 accordingly. Water will also be used for drilling, in situ jet testing, watering exposed dry stockpiles, and vehicle cleaning. The amount of water to be used for each purpose and the number of trucks per day should be quantified.
Water supplied from the Pacheco Conduit will remove water that would otherwise be delivered for other water needs in Santa Clara County. The total loss to County water supply should be quantified and possible impacts should be discussed.
Wildfire Risks
The EIR should explain the actions that will occur to mitigate fire risks associated with driving over dry grass on little used roads/track or undisturbed overland routes. Spark arrestors are specified for equipment but not other vehicles. It appears that specified best management practices and mitigation measures will not prevent ignition from hot exhaust pipes and catalytic converters. Please address how this risk of igniting dry vegetation will be mitigated. One possible mitigation measure would be to cease operations on days when high wildfire danger is forecast.
Sincerely,
Katja Irvin, AICP
Guadalupe Group Conservation Chair
Sierra Club Loma Prieta Chapter
Molly Culton
Chapter Organizing Manager
Sierra Club California