ITEM:		INFORMATIONAL ITEMS/STAFF REPORTS
22.	SEMI-ANNUAL GROUNDWATER QUALITY MONITORING REPORT
Meeting Date:			August 21, 2006	Budgeted:	Yes
From:			David A. Berger,	Program/	2.6 Hydrologic Monitoring
			General Manager	Line Item No.:	2-6-1
Prepared By:			Thomas Lindberg	Cost Estimate:	N/A
General Counsel Approval: N/A
Committee Recommendation: N/A
CEQA Compliance: N/A

SUMMARY: Water quality results from the Spring 2006 sampling of the Monterey Peninsula Water Management District’s (District’s) well network in the Carmel Valley aquifer are presented in Exhibit 22-A and briefly summarized below. Results from Spring 2005 are also provided for comparison.

BACKGROUND: The District has maintained a groundwater quality monitoring program in the Carmel Valley Aquifer since 1981 and in the Seaside Groundwater Basin since 1990. In 1996, the District conducted an assessment of its ground water quality monitoring program. Based on a review of long term data trends, it was 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 has been 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 sampled 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 2006 and Spring 2005 samplings are provided in Exhibit 22-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 22-B. Review of these water quality results indicates no significant change in overall water quality in Spring 2006 compared to samples collected in Spring 2005. As noted in the 2004 and 2005 reports, Potassium concentrations in two of the wells (16S/2E-33Q1 and 17S/2E-10B1), were slightly higher in Spring 2004, and that trend continued in Spring 2006 for well 16S/2E-33Q1, and in Spring 2006 the concentration of Potassium in well 17S/2E10B1 was also slightly higher than the previous year. There is no California Title 22 Drinking Water Standard for Potassium, and historically, Potassium levels were higher in 2002 and 2001, so there is no cause for alarm. All constituents that have established Drinking Water Standards are within acceptable limits.

It should be noted that relatively high nitrate concentrations (up to 22 milligrams per liter [mg/L]) were measured in two upper Carmel Valley monitor wells in Spring 1998, although the observed nitrate concentrations were well below the drinking water standard of 45 mg/L. The Carmel Valley Master Plan established an “action level” of 25 mg/l of nitrate due to concern about the limitations of septic systems in this unsewered portion of Carmel Valley. The relatively high readings were attributed to the flushing effect of severe storm events in the Winter of 1998. All results of more recent samplings from all three shallow wells indicate that nitrate concentrations have returned to more normal levels. In Spring 2006, nitrate levels in two wells (16S/2E-33Q1 and 17S/2E-10B1) were slightly lower that the previous year, and are less than half of the action level. Nitrate concentration was below the detection limit in the third well (17S/2E-03La) in both years.

EXHIBITS

22-A Ground Water Quality Monitoring Results for Spring 2006 and Spring 2005

22-B Map of Monitor Well Locations in Upper Carmel Valley

Revised 7/20/06

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