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Fdmmy 2000 Ham GAd~ Temouu~ !sc • 1999 A~veal Hy6dcxy ReArr ~ Page 4 ' higher than the HGSD3 sample. This indicates that the source of the manganese u upstream of the loadout. ' The field pH values meazured during the December sampling event are suspect (10.37 and 9.85 for HGSDl and HGSD3 respectively). Measured values were stgaificantly higher than the historic range and if accurate, exceed the cold-water aquatic standard of 9.0 units. However, field peaonnel ' experienced meter problems. Upon hand delivery of the samples to ACZ on the ahemoon of collection, the field personnel requested immediate laboratory pH meazurement to check the field values. Iab pH results were 8.0 and 8.1 for HGSDl and HGSD3, respectively. These values probably reflect the actual pH of Dry Creek during the sampling event. ' HGTI has compiled a list of water quahry standards for livestock This list is composed primarily of Colorado Department of Public Health and Environment (CDPHE) standards, although other agency ' standards were used if they were more stringent or if CDPHE has no standard for a particular constiruent. Table 4, Comparison of 1999 Surface Water Quality to Livestock Standards, provides a list of the livestock standards along with a cotnparison of those standards to 1999 surface water quahry ' data. Units of concentration are az listed in Table 4. Laboratory analytical reports generally report constituent concentrations az mg/1. There were no exceedances of CDPHE livestock standards for HGSD1 and HGSD3 samples during 1999. As indicated above, the December field pH meazurements exceed both promulgated cold-water aquatic and livestock standards. However, the ' field values were suspected and immediate laboratory pH measurements were requested when the samples were delivered to the laboratory The laboratory values, which are less than the promulgated standards, are probably more representative of the actual field conditions. 3.3 GROUNDWATER DATA ' Groundwater data for 1999 u presented in Appendix D, Groundwater Quality Data. Due to an oversight, HGTI did not collect a groundwater sample doting the June monitortng even[. Presently, HGTI is only monitoring alluvial groundwarer in monitoring well HGDAL3. In 1993, HG'II installed HGDAL3 az a new downdip alluvial monitoring well in response to Colorado Division of Mmerak ' and Geology (CDMG) concerns that the two existing alluvial wells, HGDALl and HGDALZ, may have been partially completed in the Lewis Shale. Groundwater quality data was colletted from monitoring wells HGDALI and HGDAL2 between 1987 and 1995. Groundwater monitoring ceased ' for HGDALl and HGDAL2 in 1995. The location of the groundwater monitoring wells are shown of Figure 1, Monitoring Site Location Map. HGTI reported in the existing, valid Permit (revtsron date October 1997) that chemistry informauon obtained in HGDAL3 is similar to the chemistry depicted ' by monitoring wells HGDALl and HGDAL2. A comparison of the 1999 groundwater quality data from momtonng well HGDAL3 against histonc ' data indicates 1999 grotmdwater quality parameters were within the range of historic values. The parameters with promulgated standard were generally less than the numenc standard. Manganese and total dissolved solids ('I'DS) were the exception. The manganese concentration was stgnificantly greater than the standard. The TDS concentration was greater than 10,000 mg/I, which indicates the ' groundwater in unsuitable for agricultural uses. The field pH value of 8.24 u within the range of historic values. However, the value may not be ' accurate due to problems with the meter. The laboratory reported value of 7.1 may be more representative of actual conditions. 1 MorymPryW~m •P.~ Bar 774018 •Srerfor5png, 61780477 •(970J 879-6260 m uu~nxrery.inn+.mMrt> ri:sim„/