Water levels in Borrego Valley have been declining for several decades. Groundwater recharge is limited due to the limited precipitation the region receives. The average groundwater recharge for the Valley is estimated to be approximately 5,000 acre-feet per year. The groundwater demand for the Valley exceeds 15,000 acre-feet per year. Due to the difference between supply and demand, the aquifer is currently in an overdraft condition whereby continued extraction at current rates is not sustainable.
However, the aquifer does hold a large volume of water in storage. It was estimated that in 1999 the volume of water in storage was approximately 1,685,000 acre-feet (Borrego Water District, 2001). Water pumped from the aquifer in excess of the natural recharge rate is derived from aquifer storage. Removal of water from storage in the aquifer results in declining water levels in the aquifer. Approximately 500,000 acre-feet of groundwater have been removed from storage over the past 50 years. The County has been monitoring water levels in the Valley for approximately 20 years and has measured declines in the northern part of the aquifer, where most agriculture is located, in excess of 50 feet over that period of time. Current rates of water level decline in some areas of the aquifer are more than 5 feet annually.
Because the Borrego aquifer is currently in an overdraft condition, groundwater production at current rates is not sustainable. If new projects propose to use water derived from groundwater in the Valley, they will ultimately contribute to the overdraft problem. No single user in the Valley is responsible for the overdraft condition. Rather, it is the cumulative impact of all users that has resulted in this condition. Additional groundwater extraction to support new projects will contribute to this cumulative impact. Projects requiring large amounts of water will have a greater cumulative impact on the groundwater resources of the Valley than smaller projects with lower water demands.
The overdraft condition in Borrego Valley is well documented and data collected over the past half century confirms this overdraft condition (Borrego Water District, 2001; Henderson, T.W., 2001; Mitten, H.T., G.C. Lines, C. Berenbrock, and T.J. Durbvin, 1988; Moyle, Jr., W.R., 1988; Netto, S 2001; San Diego County).
2. CEQA Requirements
Projects involving discretionary land use permits or approvals, such as a grading permit, subdivision of land or a major use permit for a golf course, as well as public projects such as general plan amendments, are subject to review under the California Environmental Quality Act (CEQA). As part of this review, the project’s potential cumulative impact to groundwater resources (taking the overdraft condition into consideration) must be identified and analyzed.
a. New Proposed Projects. Regarding new proposed projects, State CEQA Guidelines, Appendix G, Section VIII Hydrology and Water Quality, b), requires that the following inquiry be made with respect to groundwater quantity. Would the project:
“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 (e.g., 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)?”
Additionally, Section XVII, Mandatory Findings of Significance, requires that the following inquiry be made with respect to cumulative impacts:
“Does the project have impacts that are individually limited, but cumulatively considerable? (“Cumulatively considerable means that the incremental effects of a project are considerable when viewed in connection with the effects of past projects, the effects of other current projects, and the effects of probable future projects)?”
b. Projects With Previously Approved CEQA Documents. CEQA review of projects for which an Environmental Impact Report (EIR) or Negative Declaration (ND) has previously been approved involves an analysis of whether, due to changes in the project or surrounding circumstances or important new information, there will be new significant effects or increased severity of significant effects, or mitigation measures or alternatives which could reduce the effects but which the applicant declines to implement.
It is the policy of the Department of Planning and Land Use that CEQA evaluation of potential cumulative impacts to groundwater resources in Borrego Valley will be guided by the following principles:
1. Applicants for projects using groundwater resources In Borrego Valley are encouraged to include with their projects, offsetting groundwater use reduction measures which will make up for the project’s proposed groundwater use and result in “no net gain” in the overall rate or amount of extraction of groundwater.
The offsetting groundwater use reduction measures must save an amount of water at least equivalent to the project’s demand amount, elsewhere in Borrego Valley such that there is “no net gain” in the overall groundwater extraction in the Valley. As one example of such a measure, land could be purchased which currently has a water use associated with it. If the water use on this land were reduced by an amount equivalent to the water demand of the proposed project, then there would be “no net gain” in the amount of water extracted from the aquifer, and thus the overdraft condition would not be made worse by the proposed project. The applicant would have to propose a legally enforceable mechanism for achieving the reduction on the other land. Other examples of offsetting measures include upgrading inefficient irrigation systems, taking agricultural or golf course land out of production, or repairing leaking irrigation systems.
2. For projects where offsetting groundwater use reduction measures are not proposed as part of the project, except as provided in sections 3 and 4 below, an EIR will generally be required to be prepared, to analyze the significance of cumulative impacts to groundwater resources, to propose mitigation measures, and to consider project alternatives.
The mitigation measures considered in the EIR should include feasible offsetting groundwater use reduction measures as described above in paragraph 1. If the impacts to groundwater cannot be feasibly mitigated or avoided, the County would be required to deny the project unless the County determines that the economic, legal, social, technological, or other benefits of the proposed project outweigh its unavoidable, environmental impacts.
3. For projects with previously approved environmental documents, the project must be assessed per the requirements of Section 15162 of the State CEQA Guidelines (summarized at paragraph A.2.b above). If the project proposes to use more groundwater than initially proposed, then offsetting groundwater use reduction measures may be proposed and included in this analysis. If such measures are not included, the Section 15162 analysis may lead to a requirement to prepare a supplemental or subsequent EIR.
If a supplemental or subsequent EIR is required, it should consider feasible offsetting groundwater use reduction measures among the possible mitigation measures.
4. Proponents of some small projects may be able to demonstrate that potential cumulative impacts to groundwater resources are not significant, because the project’s incremental additional groundwater demand is not “cumulatively considerable.”
With some projects involving very small groundwater demands, applicants may be able to demonstrate that the incremental groundwater demands of their projects are not “cumulatively considerable.” To demonstrate this, applicants should prepare analyses which consider the total water supply available, the number of potential groundwater uses that are likely to be developed in the Valley (based on existing and proposed land use designations), and the gravity of the impact of allowing the small project to go forward. The inclusion of appropriate mitigation measures may also be a basis for a determination that the incremental effects of a project are not “cumulatively considerable.”
Borrego Water District, 2001. Groundwater Management Study, Report of the Technical Committee.
Henderson, T.W., 2001. Hydrogeology and Numerical Modeling of the Borrego Valley Aquifer System. Masters Thesis, San Diego State University, Fall 2001.
Mitten, H.t., G.C. Lines, C. Berenbrock, and T.J. Durbvin, 1988. Water Resources of Borrego Valley and Vicinity, San Diego County, California: Phase 2--Development of a Groundwater-Water Model. U.S. Geological Survey Water-Resources Investigations Report 87-4199.
Moyle, Jr., W.R., 1988. Water Resources of Borrego Valley and Vicinity, Phase 1-- Definition of Geologic and Hydrologic Characteristics of Basin, U.S. Geological Survey Open-File Report 82-855.
Netto, S.P., 2001. Water Resources of Borrego Valley San Diego County, California. Masters Thesis, San Diego State University, Fall 2001.
San Diego County. Groundwater Monitoring Program Data. Department of Planning and Land Use. Data from 1980 through 2003.
The County began implementing the principles outlined in the policy in January 2003, based on County interpretation and compliance with the California Environmental Quality Act (CEQA). The actual document was not finalized until November 2004, however.
Department of Planning and Land Use
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San Diego, CA 92123
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