Meeting Date:

August 16, 2010





Darby Fuerst,


2.6 Hydrologic Monitoring


General Manager

Line Item No.:



Prepared By:

Thomas Lindberg

Cost Estimate:



General Counsel Review:  N/A

Committee Recommendation:  N/A

CEQA Compliance:  N/A


SUMMARY:  Water-quality results from the Spring 2010 sampling of the Monterey Peninsula Water Management District’s (District’s) well network in the Carmel Valley aquifer are presented in Exhibit 30-A and briefly summarized below.  Results from Spring 2009 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 that time of the year. 


DISCUSSION/ANALYSIS:  Carmel Valley Aquifer Monitor Wells - Results from the Spring 2010 and Spring 2009 samplings are provided in Exhibit 30-A.  Three shallow monitor wells in the upper Carmel Valley are sampled each Spring, per the sampling schedule described above.  The locations of these sampling points are shown on the map in Exhibit 30-B.  Review of these water-quality results indicates no significant changes in overall water quality in Spring 2010 compared to samples collected in Spring 2009.  Samples collected in Spring 2010 were analyzed by Monterey Bay Analytical Services.  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 2010, the nitrate levels in two wells (16S/2E-33Q1 and 17S/2E-10B1)) were one mg/L (or one part per million) higher than Spring 2009, but remained below the action level.  Nitrate concentration in the third well (17S/2E-03La) was less than in Spring 2007, and remained below practical detection for the third year in a row, and for nine of the last ten years.



30-A    Ground Water Quality Monitoring Results for Spring 2010 and Spring 2009

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