Cal Water, as the water purveyor, has specific requirements for Water Supply Assessments (WSAs). The following is an outline of the requirements for both WSAs and WSVs (Water Supply Verifications).
Cal Water must produce and sign-off on the completed WSA.
Cal Water makes use of a third-party consultant to complete the analysis and to produce the final WSA. The WSA development will begin when payment and supporting documentation is received from the project applicant.
In California, WSAs are mandated by Senate Bill 610.
This bill requires a detailed assessment of the water supply for large development projects. Additionally, Senate Bill 221 requires a Water Supply Verification (WSV) for developments greater than 500 units, which is a formal assurance from the water purveyor. These assessments are required in the project’s environmental review documents per the California Environmental Quality Act (CEQA).
WSAs determine if the water system’s projected supplies can meet the proposed project’s demand.
The assessment covers a period of 20 years and evaluates normal, single-dry, and multiple-dry years scenarios.
WSVs require written verification
WSVs require written verification of sufficient water supply from the water supplier for residential subdivisions of 500 units or more and are required before the final subdivision map is adopted to ensure water availability before construction begins.
The following “projects” as defined by SB 610 require a WSA:
Residential Developments >500 units
Commercial Developments >1,000 persons or >250,000 sq. ft.
Hotels/Motels >500 rooms
Retail Shopping/ Business Centers >1,000 persons or >500,000 sq. ft.
Industrial/ Manufacturing/ Processing Plant or Industrial Park >1,000 persons or >40 acres or >650,000 sq. ft.
Plus:
- Mixed-use projects including any of the above
- Projects demanding water equal to or greater than 500 dwelling units
- If a public water system has fewer than 5,000 service connections:
- Any proposed residential, business, commercial, hotel or motel, or industrial development that would account for an increase of 10 percent or more in the number of existing service connections
- Any mixed-use project that would demand an amount of water equivalent to, or greater than, the amount of water required by residential development that would represent an increase of 10 percent or more in the number of the public water system’s existing service connections
Cal Water may determine that a WSA is still needed even if these requirements are not met.
CA Water Code, Sections CWC § 10910 and CWC § 10912 provide more detail on these requirements.