ITEM:		INFORMATIONAL ITEMS/STAFF REPORTS
24.	SEMI-ANNUAL GROUNDWATER-QUALITY MONITORING REPORT
Meeting Date:			February 24, 2011	Budgeted:		Yes
From:			Darby Fuerst,	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 2010 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 to collect water-quality samples from the District’s Seaside Basin monitor on a quarterly basis. The results of that sampling are reported to the Seaside Basin Watermaster Board on a quarterly basis. Results of the Fall 2009 and Fall 2010 sampling of the Seaside Basin coastal monitor wells are included in this report.

DISCUSSION/ANALYSIS:

Carmel Valley Aquifer Monitor Wells - Results from the Fall 2010 sampling are provided in Exhibit 24-A. Seven monitor wells in the lower Carmel Valley were sampled during Fall 2010, per the sampling schedule described above. An eighth well that is normally sampled in the Fall (16S/1E-13Md), was not sampled in Fall 2009 or Fall 2010 because it was submerged under high water in the Carmel River Lagoon during the sampling period. The locations of these sampling points are shown on the map in Exhibit 24-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 2009 (data originally reported in the February 25, 2010 Board packet and provided here as a reference in Exhibit 24-B). 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 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. Currently, only the deeper wells at each of the three coastal locations are sampled.

Well 16S/1W-14Jg is the deepest in the array of three wells located at the Carmel River State Beach parking lot at River Mile (RM) 0.07 (approximately 375 feet from the shoreline). Beginning in the Fall of 2005, there was a four-year trend in increased Specific Electrical Conductance (SEC) and Chloride results at this site, which reversed in Fall 2009. In the February 25, 2010 Board packet, it was noted that the significant improvement at this location relative to 2008, suggested a seaward movement of the freshwater/seawater interface which may be attributable to the later season flows in the lower reaches of the Carmel River in 2009 compared to 2008. Results from Fall 2010, however, show SEC and Chloride levels have returned to the earlier trend and were higher than Fall 2008 (Exhibit 24-E). Because there were episodes of ocean waves overtopping the beach berm at this site within a week of the sampling event, it is postulated that there could be a component of surface-water contamination at this location. The wellhead was damaged by heavy equipment removing sand from the parking lot at Carmel River Lagoon State Beach several years ago, and the trend could have more to do with modifications of the wellhead than a change in the freshwater/seawater interface. Staff will attempt to pump for an extended period to be sure and evacuate any water standing in the casing prior to the next sampling event and will watch for any indication of further potential surface-water contamination at this site. 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.

Well 16S/1E-23E4, located 6.53 miles upstream from the mouth of the Carmel River, showed significant improvement in overall water quality in 2009 relative to 2008. In the February 25, 2010 Board Packet, it was suggested that the improvement may be attributable to wellhead improvements at this site that were make in Summer 2008 to reduce potential flooding along the roadside where this well is located. However, water-quality results from Fall 2010 were again much closer to the results from Fall 2008. It is possible that the well cap was not sealed tightly enough to prevent surface-water contamination in spite of the wellhead improvements. Staff will continue to monitor this site to ensure the wellhead is secure from surface-water sources.

Well 16S/1E-23La, located 6.72 miles upstream from the river mouth, does not show a significant change in 2009 relative to 2008, but a graph of SEC and Chloride is included to track long-term trends as was described in the March 21, 2009 Board packet (Exhibit 24-F).

Well 16S/1E-24N5, located 8.02 miles upstream from the river mouth, showed significant increases in major inorganic constituents in 2009 relative to 2008, but the results from Fall 2010 were lower than either year for all constituents. The anomalous results for Fall 2009 may also be due to surface water getting into the well, as this location is in the middle of a roadway. Staff will continue to monitor this site to ensure the wellhead is secure from surface-water sources.

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 to “micro-purging” wells, which is generally less destructive to the well and gravel pack, less dangerous for the operator, but also more time consuming. In Fall 2010, 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 2010 due to a temporary obstruction that prevented collecting samples. Results of water-quality sampling from 2010 and 2009 for the Seaside wells are provided in Exhibit 24-A and Exhibit 24-B, respectively. Because laboratory results for the Fall 2010 samples needed to be received and processed earlier than in years prior to 2008 in order to complete an Annual Report to the Seaside Groundwater Basin Watermaster, the Seaside wells were actually sampled in July and August of 2010. The locations of the Seaside monitor wells are shown on the map in Exhibit 24-D. 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 these wells that are completed in the two principal aquifer units -- the Paso Robles Formation (i.e., shallower unit) and Santa Margarita Sandstone (i.e., deeper unit) -- in this area of the Seaside Groundwater Basin at the present time. Results for most constituents in most of the wells were not significantly different in 2010 relative to 2009, with few exceptions. As noted in the February 25, 2010 Board Packet, wells 15S/1E-12Fa and 15S/1E-12Fc marked increases in Iron and Manganese concentrations were observed in 2009 relative to 2008, and while Iron concentration dropped in the shallower well in 2010, it showed a notable increase in the deeper well for the second consecutive year. Manganese concentrations dropped in both wells in 2010 relative to 2009. A marked increase in Iron concentration was also observed in well 15S/1E-11Pb in 2010. 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

24-A Groundwater-quality Monitoring Results - Fall 2010

24-B Groundwater-quality Monitoring Results - Fall 2009

24-C Location of MPWMD Carmel Valley Water-quality Monitoring Wells

24-D Location of MPWMD Seaside Basin Water-quality Monitoring Wells

24-E Water-quality Results in Well 16S/1W-14Jg in Carmel Valley

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

U:\staff\word\boardpacket\2011\20110224\InfoItems\24\item24.doc