ITEM:		INFORMATIONAL ITEMS/STAFF REPORTS
21.	SEMI-ANNUAL GROUNDWATER-QUALITY MONITORING REPORT
Meeting Date:			December 10, 2012	Budgeted:	Yes
From:			David Stoldt,	Program/	Hydrologic Monitoring 2.6
			General Manager	Line Item No.:	2-6-1 G, and 2-6-2 D
Prepared By:			Joe Oliver/	Cost Estimate:	N/A
			Tom Lindberg
General Counsel Review: N/A
Committee Recommendation: N/A
CEQA Compliance: N/A

SUMMARY: Water-quality results from the Fall 2012 sampling of the Monterey Peninsula Water Management District’s (District’s) monitor well networks in the Carmel Valley aquifer and the coastal areas of the Seaside Groundwater Basin are presented and briefly summarized below.

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, collection of samples from the Carmel Valley monitor wells is conducted on an annual basis. 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 in Fall, to coincide with the historically higher nitrate concentrations in these respective areas. Beginning in 2007, the District was retained by the Seaside Basin Watermaster (Watermaster) to collect water-quality samples from the District’s Seaside Basin coastal monitor wells on a quarterly basis under the Watermaster’s Monitoring and Management Program. The results of that sampling are reported to the Watermaster Board on a semi-annual basis. Results of the Fall 2011 and Fall 2012 sampling of the Seaside Basin coastal monitor wells are included in this report.

DISCUSSION/ANALYSIS:

Carmel Valley Aquifer Monitor Wells - Results from the Fall 2012 sampling are provided in Exhibit 21-A. Six monitor wells in the lower Carmel Valley were sampled during Fall 2012, per the sampling schedule described above. A seventh well that is normally sampled in the Fall (16S/1E-13Md), was not sampled in Fall 2012, Fall 2011 or Fall 2010 because it was submerged under high water in the Carmel River Lagoon during the sampling period. Another nearby well that had been sampled during this period (16S/1W-14Jg) was destroyed by flooding in March 2011 when the river scoured away the south end of the Carmel River State Beach parking lot. The locations of the lower valley sampling points are shown on the map in Exhibit 21-C. Review of these water-quality results indicates that, in general, there are minor changes in overall water quality compared to samples collected in 2011 (data originally reported in the January 23, 2012 Board packet and provided here as a reference in Exhibit 21-B). It should be noted that the Fall 2011 data in Exhibit 21-B include three wells in the upper Carmel Valley Aquifer that were not sampled during the normal collection time in Spring 2011. Changes in water quality for specific wells are discussed below. Staff is particularly interested in tracking indicators of potential seawater intrusion in the coastal portion of Carmel Valley. Accordingly, three clustered sets of wells were established west of Highway 1, with each set being made up of three wells completed at different depths. Review of historical data indicated that the shallower and intermediate wells in the coastal area are subject to the mixing of fresh water and saline water as high tides and surf overtop the sand berm between the lagoon and the ocean. This contributes to episodic mixing within the shallower and intermediate zones of the aquifer, but is not indicative of larger-scale seawater intrusion into the aquifer. All three wells in the cluster closest to the ocean were destroyed by the river in March 2011, and all three of the wells in the next closest cluster to the ocean were inaccessible due to high water during the Fall 2012 sampling period, so currently, only the sample results from the deeper well at one of the three coastal locations is available, as described above.

Well 16S/1W-13Lc is the deepest in the array of three wells located State Parks property near the Carmel Area Wastewater District treatment plant at River Mile (RM) 0.65, currently the most proximate well to the ocean in Carmel Valley that is available for sampling. There was an increasing trend in Specific Electrical Conductance (SEC) and Chloride from 2008 to 2011, after a noticeable decline from 2006 to 2008, but in 2012 both constituents were lower than in 2011 (Exhibit 21-D). Current levels are below peak levels observed at this location in Water Year 2001, however. Additional background on historical water-quality at the coastal monitor well sites can be found in District Technical Memorandum 90-04, Summary of Carmel Valley Groundwater-quality from Coastal Monitor Wells, which is available at the District office. Staff will continue to track future results for trends that might indicate significant changes in concentrations of these or other constituents in the coastal area of the aquifer.

Results for well 16S/1E-23E4, located 6.53 miles upstream from the mouth of the Carmel River, show a slight decline in overall water quality in 2012 relative to 2011. A decline in water quality was noted at this site in 2007, and in 2008 staff made improvements to the wellhead at this site to reduce potential flooding along the roadside where this well is located. Attempts have been made to improve results through air-lifting and more extensive and rigorous pumping, but due to the relatively small amount of available saturation below the water table at this well, these efforts have had limited success. Staff will continue to monitor the site to ensure the wellhead is secure from surface-water sources.

Results for well 16S/1E-23La, located 6.72 miles upstream from the river mouth, show an increase in both SEC and Chloride in 2012 relative to 2011. In fact, both SEC and Chloride were higher in 2012 than any year since 2006 (Exhibit 21-E). Other constituents were not significantly changed from last year.

Seaside Groundwater Basin Coastal Monitor Wells - Since 1990, the District has been collecting water-quality samples from coastal monitor wells in the Seaside Groundwater Basin, for the purposes of water-quality characterization and sea-water intrusion monitoring. In 2009 District staff switched from air-lifting samples from wells in Seaside to “micro-purging”, which is generally less destructive to the well and less dangerous to the operator, but requires additional sampling time at each well. In Fall 2012, 11 dedicated monitor wells at six different sites were sampled. One well (15S/1E-23Cb) that is part of the network was not sampled in 2012 due to a temporary obstruction that prevented collection of samples. Results of water-quality sampling from 2012 and 2011 for the Seaside wells are provided in Exhibit 21-A and Exhibit 21-B, respectively. Because laboratory results for the Fall 2012 samples needed to be received and processed earlier than in years prior to 2008 in order to complete an Annual Report to the Watermaster, six Seaside wells were actually sampled in June and July 2012, while the remaining six were sampled in late September 2012. The locations of the Seaside monitor wells are shown on the map in Exhibit 21-F. These wells are completed in the two principal aquifer units -- the Paso Robles Formation (i.e., shallower unit) and Santa Margarita Sandstone (i.e., deeper unit) – of the Seaside Groundwater Basin. 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 at the locations and depths of these monitor wells at the present time. Results for most constituents in most of the wells were not significantly different in 2012 relative to 2011, with few exceptions. Marked increases in Iron concentration in wells 15S/1E-11Pb and 15S/1E-12Fa were noted in 2010, but in 2011 the concentrations dropped significantly in those wells. In 2012, the Iron concentration in well 15S/1E-11Pb had dropped below practical quantifiable limits, but in well 15S/1E-12Fa it had increased significantly relative to results from 2011. Staff will continue to track results for all wells for trends that might indicate significant changes in the basin. A more complete historical summary of the Seaside Basin coastal groundwater-quality data is contained in District Technical Memorandum 97-02 Seaside Basin Coastal Monitor Wells: Ground Water-quality Monitoring Results, 1990-1996, which is available at the District office.

EXHIBITS

21-A Groundwater-quality Monitoring Results - Fall 2012

21-B Groundwater-quality Monitoring Results - Fall 2011

21-C Location of MPWMD Lower Carmel Valley Water-quality Monitoring Wells

21-D Water-quality Results in Well 16S/1W-13Lc in Carmel Valley

21-E Water-quality Results in Well 16S/1E-23La in Carmel Valley

21-F Location of MPWMD Seaside Basin Water-quality Monitoring Wells

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