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Marrb 2007 Hgden Guttb Ioadaut - 2006 AuuualHydrology Report ~ Page S While sulfate and total dissolved solids (TDS) do not have agriculrure standazds promulgated in Colorado, the Wyoming Depaztment of Environmental Quality has established livestock drinking water standazds for these constituents that can be used as benchmark values to assess the appropriateness of water for agriculture use. Sulfate and TDS concentrations commonly exceed the WDEQ values. • sulfate (guideline of 500 mg/I) HGSDl - 5/8/06: 960 mg/1; 10/12/06: 1,420 mg/1 HGSD3 - 5/8/06: 1,180 mg/1; 10/12/06: 1,810 mg/1 • total dissolved solids (guideline of 2,500 mg/I): HGSDl -10/12/06: 2,570 mg/1 HGSD3 -10/12/06: 3,270 mg/1 While [here values were greater than the benchmazk values used by WDEQ, historic values for these constituents at both locations typically exceeded the respective benchmazk values. Time-trend plots of manganese, sulfate and TDS concentrations aze presented in Appendix C. 3.3 GROUNDWATER DATA Groundwater data for 2006, as well as historic data collected since 1993 aze presented in Appendix D, Groundwater Quality Data. In 1993, HGTI installed HGDAL3 as a "new" downgradient alluvial monitor well in response to CDMG concerns that the two existing alluvial wells, HGDALl and HGDAL2, might have been paztially completed in the Lewis Shale, which could comprise the data. Groundwater quality data was collected from monitoring wells HGDALl and HGDAL2 between 1987 and 1995. Groundwater monitoring of these two monitor wells ceased in 1995; these two wells ue inactive. As part of the TR-06 adequacy review, CRMS raised concerns about the lack of an upgradient alluvial monitor well at the Loadout. Consequendy, HGTI installed a "new" upgradient well, HGDAL4 in November 2005. The locations of the groundwater monitoring wells aze shown on Figure 1, Moxitoring Site Lacationr, The spring runoff monitoring event occurred on May 8, 2006. The fall monitoring event was conducted on October 12, 2006. In general, the alluvial groundwater concentrations from HGDAL3 in the 2005 samples were similar to previously observed values. All constituent concentrations were within historic ranges. While the manganese concentrations exceeded the manganese numeric standard (0.2 mg/I) in both samples, the values were within the historic range. The observed concentrations in the HGDAL4 sample were generally similaz to what was observed in the HGDAL3 samples. Most trace element concentrations were reported as less than the method detection ]unit. There were reported concentrations Eor azsenic (October sample: 0.0013 mg/1), boron, cadmium (October sample: 0.0002 mg/1) and manganese. Major ionic constituents (i.e., calcium, magnesium, sodium, bicarbonate, chloride and sulfate) were generally less than their respective values in the corresponding HGDAL3 sample. Time trend plots for common constiruents aze presented in Appendix D Hydro-Environmental Solutions, Inc. P.O. Bax 772996 57 70r^ Strzet, Suite B Steamboat Spring; CO 80477 (970) 871-6725