ITEM:		INFORMATIONAL ITEMS/STAFF REPORTS
23.	SEMI-ANNUAL GROUNDWATER-QUALITY MONITORING REPORT
Meeting Date:			January 23, 2011	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 2011 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 coastal monitor wells on a quarterly basis. The results of that sampling are reported to the Seaside Basin Watermaster Board on a semi-annual basis. Results of the Fall 2010 and Fall 2011 sampling of the Seaside Basin coastal monitor wells are included in this report.

DISCUSSION/ANALYSIS:

Carmel Valley Aquifer Monitor Wells - Results from the Fall 2011 sampling are provided in Exhibit 23-A. Six monitor wells in the lower Carmel Valley were sampled during Fall 2011, per the sampling schedule described above. A seventh well that is normally sampled in the Fall (16S/1E-13Md), was not sampled in Fall 2011 or Fall 2010 because it was submerged under high water in the Carmel River Lagoon during the sampling period. Another well that had been sampled during this period was destroyed by flooding in March of 2011 when the river scoured away the south end of the Carmel River State Beach parking lot. Three other wells in upper Carmel Valley that are usually sampled in the Spring were also sampled in Fall 2011. Due to other demands for time, these three wells were not sampled in the Spring, but were sampled in the Fall rather than missing a full year of sample collection. The locations of the sampling points are shown on the maps in Exhibits 23-C and 23-D. Review of these water-quality results indicates that, in general, there are minor changes in overall water quality compared to samples collected in 2010 (data originally reported in the August 16, 2010 and February 24, 2011 Board packets and provided here as a reference in Exhibit 23-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 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 2011, and all three of the wells in the next closest cluster to the ocean were inaccessible due to high water during the sampling period, so currently, only the deeper well at one of the three coastal locations is sampled.

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 is an increasing trend in Specific Electrical Conductance (SEC) and Chloride from 2008 to 2011, after a noticeable decline from 2006 to 2008 (Exhibit 23-E). 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.

Well 16S/1E-23E4, located 6.53 miles upstream from the mouth of the Carmel River, shows a slight decline in overall water quality in 2011 relative to 2010. 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 not been successful. Staff will continue to monitor the 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 2011 relative to 2010, 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 23-F).

Well 16S/2E-33Q1, located 12.52 miles upstream from the river mouth, is one of the three upper valley wells that is normally sampled in the Spring, but was sampled in the Fall in 2011. This well was replaced with a new monitor well approximately 100 feet away in August 2007 to accommodate a new septic system on a neighboring parcel. The concentration of Iron increased by two orders of magnitude and the concentration of Manganese increased by one order of magnitude between 2010 and 2011 for unknown reasons. This well may be a good candidate for more rigorous development through airlifting, and in any case, staff will continue to watch for changes.

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 at each well. In Fall 2011, 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 2011 due to a temporary obstruction that prevented collection of samples. Results of water-quality sampling from 2011 and 2010 for the Seaside wells are provided in Exhibit 23-A and Exhibit 23-B, respectively. Because laboratory results for the Fall 2011 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 2011. The locations of the Seaside monitor wells are shown on the map in Exhibit 23-G. 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 2011 relative to 2010, with few exceptions. Marked increases in Iron in wells 15S/1E-11Pb and 15S/1E-12Fa were noted in 2010, but in 2011 the concentrations dropped significantly in those wells. 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

23-A Groundwater-quality Monitoring Results - Fall 2011

23-B Groundwater-quality Monitoring Results - Fall 2010

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

23-D Location of MPWMD Upper Carmel Valley Water-quality Monitoring Wells

23-E Water-quality Results in Well 16S/1W-13Lc in Carmel Valley

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

23-G Location of MPWMD Seaside Basin Water-quality Monitoring Wells

U:\staff\Boardpacket\2012\20120123\InfoItems\23\item23.docx