Cost Estimate: N/A

General Counsel Approval: N/A

Committee Recommendation: N/A

CEQA Compliance: N/A

SUMMARY: Water quality results from the Spring 2003 sampling of the Monterey Peninsula Water Management District’s (District) well monitoring network in the Carmel Valley aquifer are presented and briefly summarized below.

BACKGROUND: From 1981 through 1994, the District worked cooperatively with the Monterey County Water Resources Agency (MCWRA), which provided ground water data collection and water quality analysis services to the District. In 1995 the District assumed all field data collection responsibilities and contracted directly with the Monterey County Consolidated Chemistry Lab to conduct the water quality analyses.

In 1996, as part of the District’s Strategic Plan development, the District conducted an assessment of the ground water quality monitoring program. As a result, the District determined that certain modifications could be made to the sampling schedules in both the Carmel Valley and Seaside Basins without compromising the effectiveness of the program. Accordingly, collection of samples from the Carmel Valley monitor wells was reduced from semi-annual to annual. The sampling schedule for Carmel Valley is staggered, with upper valley wells (i.e., upgradient of the Narrows), sampled in Spring and lower Carmel Valley wells in Fall, to coincide with the historically higher nitrate concentrations in these respective areas. Collection of samples from the Seaside Basin monitor wells was also reduced to once per year in Fall, coinciding with the historically low water levels in the basin at this time of the year.

DISCUSSION/ANALYSIS: Carmel Valley Aquifer Monitor Wells - Results from the Spring 2003 and Spring 2002 samplings are provided in Exhibit 6-A. Three shallow monitor wells in the upper Carmel Valley are sampled each Spring, as per the sampling modification described above. The locations of these sampling points are shown on the map in Exhibit 6-B. Review of these water quality results indicates no significant change in overall water quality compared to samples collected in Spring 2002. Specifically, most of the constituents monitored were reported slightly lower in Spring 2003 as compared to Spring 2002, with the exceptions of slight increases in sulfate in the well farthest downstream (Number 16S/2E-33Q1), although the measured level (85 milligrams per liter [mg/L]) is significantly below the California Title 22 drinking water standard for sulfate (the recommended level is 250 mg/L). In fact, all constituents for which drinking water standards exist remain within acceptable limits.

It should be noted that in Spring 1998, relatively high nitrate concentrations (up to 22 mg/L) were measured in two upper Carmel Valley monitor wells (Numbers 16S/2E-33Q1 and 17S/2E10B1), although the observed nitrate concentrations were well below the drinking water standard of 45 mg/L. The relatively high readings were attributed to the flushing effect of severe storm events in the Winter of 1998. All of the more recent results of sampling from the three upper Carmel Valley wells indicate that nitrate concentrations have returned to more normal levels.

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