ITEM: CONSENT CALENDAR
3. RECEIVE SEMI-ANNUAL GROUNDWATER QUALITY MONITORING REPORT
Program/Line Item No.: 2.6
Staff Contact: Joe Oliver/ Hydrologic Monitoring/2-6-1 H. and 2-6-2 D.
Tom Lindberg Cost Estimate: Budgeted Amount $7,000
General Counsel Approval: NA
CEQA Compliance: NA
SUMMARY: Water quality results from the Fall 2002 sampling of the Monterey Peninsula Water Management District=s (District) monitor well networks in the Carmel Valley aquifer and Seaside Coastal Ground Water Subareas are presented and briefly summarized below.
RECOMMENDATION: This report is for information purposes only. The Board should review the report and provide staff with any comments or questions. Staff will make any needed revisions and finalize the report, if this item is approved with the Consent Calendar.
BACKGROUND: Since the inception of the District=s ground water quality monitoring program in 1981, the District has worked cooperatively with the Monterey County Water Resources Agency (MCWRA), which provided data collection and analysis services to the District. In 1995, however, District staff assumed all field data collection responsibilities and now works directly with the Monterey County Consolidated Chemistry Lab to conduct the water quality analyses, as a cost saving measure.
As part of the District=s Strategic Plan, District staff conducted an assessment of the ground water quality monitoring program in 1996. Based on review of the long-term data trends, it was determined that some 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 now staggered, with upper valley wells (i.e., upgradient of the Narrows) being 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 has also been reduced to once per year in Fall, coinciding with the historically low water levels in the basin at this time of the year. This sampling reduction results in an annual savings of approximately $3,600 in laboratory costs for the program.
DISCUSSION/ANALYSIS: Carmel Valley Aquifer Monitor Wells - Results from the Fall 2002 sampling are provided in Exhibit 3-A. Fourteen monitor wells in the lower Carmel Valley were sampled during the Fall of 2002, as per the sampling modification described above. The locations of these sampling points are shown on the maps in Exhibit 3-C. Review of these water quality results indicates that, in general, there are minor changes in overall water quality compared to samples collected in Fall 2001 (data reported in the February 28, 2002 Board packet and provided here in Exhibit 3-B). It should be noted that the analysis for several constituents (i.e., magnesium and potassium) at one well, 16S/1W-14Jf, are suspect, as they are considerably higher than the previous report with otherwise similar overall water quality. Staff plans to follow up to confirm these measurements. This well is one of an array of three wells, (16S/1W-14Jh, f and g), located closest to Carmel Bay. From the graphs provided herein as Exhibit 3-D and Exhibit 3-E, it can be seen that although specific conductance and chloride concentrations were higher in both the shallow and intermediate wells in Fall 2002 relative to Fall 2001, these constituents were still significantly lower in all three wells in Fall 2002 relative to the six-year high in Fall 1997. Staff will continue to track future results for trends that might indicate significant changes in concentrations of these or other constituents.
Seaside Coastal Subareas Monitor Wells - Since 1990, the District has been collecting water quality samples from coastal monitor wells in the Seaside Ground Water Basin, for the purposes of water quality characterization and sea-water intrusion monitoring. In Fall 2002, 10 monitor wells were sampled. Two wells that are usually sampled in the Fall, 15S/1E-15K4 and 15S/1E-15K5, were not sampled in 2002 due to time constraints and the expense of renting a large compressor necessary to conduct the sampling in Seaside wells, which are considerably deeper than the Carmel Valley monitor wells. It is anticipated that these wells will be sampled again along with the other wells in the Seaside Ground Water Basin monitor network in Fall 2003 and subsequent years. Results of water quality sampling from Fall 2002 and Fall 2001 for the Seaside wells are provided in Exhibit 3-A and Exhibit 3-B, respectively. The locations of the Seaside wells are shown on the map in Exhibit 3-F. These results indicate little change from previous results over the period of record for the existing wells, and that there is no indication of sea-water intrusion in this area of the Seaside Ground Water Basin at the present time. A more complete historical summary of the Seaside Basin coastal ground water quality data is contained in District Technical Memorandum 97-02, which is available at the District office.