Hydrology and Water Resources. Surface water is limited within the Covered Area, with lands containing very low drainage density and no named perennial creeks (Xxxxxxxx et al. 2007). Precipitation is highly variable annually and the region is susceptible and adapted to drought conditions (Xxxxxxxxxx 1984; Muhs and Xxxxxxxx 1995; Xxxxxxxx and Xxxx 1998). Precipitation is captured in seasonal intermittent pools and playas that provide water for wildlife and vegetation (Machenberg 1984; Xxxxxxxx and Xxxx 1998). Precipitation also recharges near- surface groundwater, which may act as a stabilizer of sand dunes directly or indirectly through growth of stabilizing vegetation (Machenberg 1984; Muhs and Xxxxxxxx 1995). The semiarid climate of this region contributes to groundwater fluctuations, which result in rapid shifts in the natural landscape (Muhs and Xxxxxxxx 1995). Given the limited surface water available, groundwater from aquifers is the primary water source for all activities in the Covered Area. Three major and four minor aquifer systems underlie the Covered Area, consisting of the Xxxxxxx-Trinity (Plateau), Ogallala, and Pecos Valley major aquifers and the Capitan Reef Complex, Dockum, Xxxxxxx-Trinity (High Plains), and Rustler minor aquifers (Xxxxxxxx et al. 2007). The Pecos Valley and Dockum Aquifers underlie most of the Covered Area and the Ogallala Aquifer underlies a minor northern portion of the Covered Area in Xxxxxxx and Xxxxxx Counties (Figure 3.1 in Xxxx 2019); these three aquifers are therefore the focus of this analysis of hydrology and water resources. The Covered Area also contains localized perched aquifers situated within but above the regional aforementioned aquifers (Machenberg 1984). Perched aquifers are formed where a semi-impermeable layer such as caliche prevents water from percolating into deeper sediments and underlying aquifers creating localized accumulation of water and ponding (Machenberg 1984). The depth and volume of the perched aquifer is determined by the shape and size of the semi-impermeable layer, and climate conditions which are highly variable in this region and thus provide a limited and unpredictable supply of water (Xxxxxx et al. 2020). Ponded water from these perched aquifers may be ephemeral, evaporating with cessation of precipitation, and become enveloped by shifting sand dunes (Machenberg 1984). Because of the separation of groundwater between a perched aquifer and the underlying aquifer by the semi- impermeable layer, groundwater uses...
Hydrology and Water Resources. Based on the thresholds established by Senate Bill 610, the proposed project would require a water supply assessment (WSA) to determine the water demand of the project and the water supplier’s (San Xxxx Water Company) ability to serve the project based on projected water supplies and planned growth in its service area. San Xxxx Water Company typically prepares WSAs for development projects in their service area. It is assumed that the County will coordinate with the San Xxxx Water to have the WSA prepared and provided to DJP&A. The project site is located outside the one percent chance flood area due to the flood control improvements implemented on the Xxxxxxxxx River. The EIR will discuss the potential for flooding from creek overflow, dam failure, and other disasters to impact future development on the site. Analysis of the project’s consistency with applicable local policies and regional stormwater permits will be based on a stormwater control plan to be provided to DJP&A by the County. While the site is currently developed, it would not qualify as infill development (because the site is not constrained by size and would have sufficient land area to implement non-mechanical stormwater treatment) and, as a result, the stormwater control plan will need to meet the most recent Low Impact Development (LID) standards established by the Regional Water Quality Control Board. It is assumed that a detailed stormwater control plan will be prepared by the project civil engineer and provided to DJP&A as part of the plan set for the Xxxxxx site. For the remaining parcels, it is assumed that the County will provide general treatment options that will be incorporated into future development plans. As the project site is located within the San Xxxx City limits, all utilities are provided by the City. Based on information provided by the project civil engineer, DJP&A will address the available capacity of existing water, sanitary sewer, and storm drain lines to serve the proposed development. The sanitary sewer analysis will be based on modeling of the existing system which will be completed by the County and provided to DJP&A. As part of the sanitary sewer analysis, the EIR will also address the capacity of the water pollution control plant and the City of San Jose’s capacity allocation. The capacity of existing landfills and the potential increase in solid waste generation will also be addressed. Mitigation measures will be developed to reduce identified infrastructur...
