Meeting Date:

August 20, 2007





David A. Berger,


2.6 Hydrologic Monitoring


General Manager

Line Item No.:



Prepared By:

Thomas Lindberg

Cost Estimate:



General Counsel Approval:  N/A

Committee Recommendation:  N/A

CEQA Compliance:  N/A


SUMMARY:  Water quality results from the Spring 2007 sampling of the Monterey Peninsula Water Management District’s (District’s) well network in the Carmel Valley aquifer are presented in Exhibit 26-A and briefly summarized below.  Results from Spring 2006 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. Currently, 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 coastal water quality monitor wells is conducted once per year in Fall, coinciding with the seasonally low water levels in the basin at this time of the year. 


DISCUSSION/ANALYSIS:  Carmel Valley Aquifer Monitor Wells - Results from the Spring 2007 and Spring 2006 samplings are provided in Exhibit 26-A.  Three shallow monitor wells in the upper Carmel Valley are sampled each Spring, as per the sampling schedule described above.  The locations of these sampling points are shown on the map in Exhibit 26-B.  Review of these water quality results indicates no significant changes in overall water quality in Spring 2007 compared to samples collected in Spring 2006.  Samples collected in Spring 2007 were analyzed by Monterey Bay Analytical Services (MBAS), which is closer and less expensive than the Monterey County Consolidated Chemistry Lab (MCCCL).  In fact, MBAS is able to provide analysis of five additional chemical constituents or characteristics for a lower cost than MCCCL, so more constituents are shown on the results for Spring 2007 than for Spring 2006.   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 un-sewered 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 2007, 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 2 mg/l or less in the third well (17S/2E-03La) in both years.



26-A    Ground Water Quality Monitoring Results for Spring 2007 and Spring 2006

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



Revised 7/30/2007