ITEM:		INFORMATIONAL ITEMS/STAFF REPORTS
21.	SEMI-ANNUAL GROUNDWATER QUALITY MONITORING REPORT
Meeting Date:			December 9, 2013	Budgeted:	Yes
From:			David Stoldt,	Program/	2.6 Hydrologic Monitoring
			General Manager	Line Item No.:	2-6-1
Prepared By:			Thomas Lindberg	Cost Estimate:	N/A
General Counsel Review: N/A
Committee Recommendation: N/A
CEQA Compliance: N/A

SUMMARY: Water-quality results from the Spring 2013 sampling of the Monterey Peninsula Water Management District’s (District’s) well network in the Carmel Valley aquifer are presented in Exhibit 21-A and briefly summarized below. Results from Fall 2011 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 Summer, 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 2013 and Fall 2011 samplings are provided in Exhibit 21-A. Three shallow monitor wells in the upper Carmel Valley are normally sampled each Spring, per the sampling schedule described above. The wells were not sampled in Spring 2011. Due to other time constraints, they were sampled in Fall 2011 rather than missing a full year of sample collection. Since they had just been sampled in Fall 2011, they were also not sampled in Spring of 2012, but are now back on the original Spring sampling schedule. The locations of these sampling points are shown on the map in Exhibit 21-B. Review of these water-quality results indicates no significant changes in overall water quality in Spring 2013 compared to samples collected in Fall 2011. The only change noted is that the 2011 anomalous spike in iron concentration in one well, 16S/2E-33Q1, dropped back to expected levels in Spring 2013. Samples were analyzed by Monterey Bay Analytical Services. All constituents that have established Drinking Water Standards are within acceptable limits in Spring 2013.

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 2013, the nitrate level in one well (17S/2E-10B1) was three mg/L higher than Fall 2011, but remained below the action level. The nitrate level in another well (16S/2E-33Q1) was 1.4 mg/L less than in Fall 2011, and nitrate concentration in the third well (17S/2E-03La) remained below the practical detection limit.

EXHIBITS

21-A Groundwater Quality Monitoring Results for Spring 2013 and Fall 2011

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

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