Hydrology and Water Quality CEQA Mitigation Measures

Summary

The California Environmental Quality Act (CEQA Overview) requires that state and local agencies consider and disclose the potential environmental impacts of a proposed project. CEQA states that projects should not be approved as proposed if there are feasible alternatives or feasible mitigation measures available which would substantially lessen the significant environmental effects of such projects (PRC § 21002).

Part of the CEQA process involves determining the type of environmental impacts likely to result. For hydrology and water quality, the CEQA Handbook defines impacts as the need to assess whether the project will affect surface and groundwater resources (including aquifer characteristics and water quality), whether runoff will be generated, that could affect flooding or drainage characteristics, or whether flooding from storm events or dam failure inundation might result.

The hydrology and water quality section of an environmental impact report should also include information on the hydrological characteristics of the site prior to any proposed project. These include existing water bodies, drainage patterns, flood plains, existing drainage and/or flood control facilities, groundwater recharge potential and surface and groundwater quality.

The availability of water supplies and infrastructure to serve project demand are addressed in the [Public Services and Utilities and Energy] section of the CEQA Handbook.

Standards of Significance

Standards of significance must be determined for the following potential hydrology and water quality environmental impacts.

Will the proposed project:

• Violate any water quality standards or waste discharge requirements;

• Substantially deplete groundwater supplies or interfere substantially with groundwater recharge such that there would be a net deficit in aquifer volume or a lowering of the local groundwater table level (i.e., the production rate of pre-existing nearby wells would drop to a level which would not support existing land uses or planned uses for which permits have been granted);

• Substantially alter the existing drainage pattern of the site or area, including through the alteration of the course of a stream or river, in a manner which would result in substantial erosion or siltation on- or off-site;

• Create or contribute runoff water which would exceed the capacity of existing or planned stormwater drainage systems or provide substantial additional sources of polluted runoff;

• Otherwise substantially degrade water quality;

• Place housing within a 100-year flood hazard area, as mapped on a federal Flood Hazard Boundary or Flood Insurance Rate Map or other flood hazard delineation map;

• Place structures within a 100-year flood hazard area that would impede or redirect flood flows;

• Expose people or structures to a significant risk of loss, injury or death involving flooding, including flooding as a result of the failure of a levee or dam; or

• Inundation by seiche, tsunami, or mudflow

Groundwater

Summary of Current Groundwater Supplies

The Monterey Bay Area is a unusual in that most farms and municipalities rely primarily on groundwater, but more water is pumped out than recharged to the aquifer on an average yearly basis. When this overdraft condition occurs in wells near the coast, it allows for seawater intrusion. The Pajaro Valley, which surrounds the City of Watsonville and Salinas Basin aquifers have been in a state of overdraft for many years and have sea water intrusion in the coastal areas. In both cases, increased agricultural production and urban development have accelerated the rate of intrusion. Improvements to Monterey Peninsula's water supply system are needed to provide a buffer against the impacts of dry years in which shortages rapidly develop due to inadequate storage on the Carmel River and increased pumping and overdraft of ground water basins. (SWRCB). Water agencies in these areas are seeking to combat the problems of groundwater supply and seawater intrusion through increased conservation, aquifer recharge projects, like the Salinas Valley Water Project (SVWP), and the use of recycled water for irrigation.

Groundwater Impact Mitigation Plans

Under CEQA, proposed projects must outline mitigation measures designed to offset impacts to groundwater quality and supply. A review of Mitigated Negative Declarations (MND) and Environmental Impact Reports (EIR) yielded these plans for lessening the the impacts to groundwater likely to result from new development (SWRCB).

Type	Project	Level of Significance	Mitigation Plan
EIR	Ferrini Ranch - 870 acres/ 146 houses	Less than significant	The property owner contributes financially towards the SVWP, so the proposed project is considered to have a long-term sustainable groundwater supply, and this would be considered a less than significant impact.
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Links

• ENVS 560/L Watershed Systems
• CEQA Overview

Disclaimer

This page may contain student work completed as part of assigned coursework. It may not be accurate. It does not necessary reflect the opinion or policy of CSUMB, its staff, or students.