HYDRO28086

• Permit No: M1980233
• IBM Index Class Name: Hydrology
• Doc Date: 12/7/1998
• Doc Name: COSTILLA LANDFILL PIT COSTILLA CNTY COLO
• From: GREYSTONE
• To: DMG
• Media Type: D
• Archive: No

November 30, 1998
Mr. James C. Stevens
State of Colorado
Division of Minerals and Geology
Department of Natural Resources n `~
1313 Sherman Street, Room 215 C~ ' 7~
Denver, Colorado 80203 'f /1- D"
12E: Castilla Landfill Pit, Costilla County, Colorado
Dear Mr. Stevens:
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RECEIVED
DEC 07 1998
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Greystone is submitting this letter on behalf of Costilla County to provide you with the data collected
during the quarterly groundwater monitoring and sampling site visit conducted on September 9, 1998 at
the above referenced site.
A regional site map is provided as Figure 1. A site map displaying [he location of the monitor wells is
provided as Figure 2. A groundwater elevation map is included as Figure 3. Groundwater elevations
were calculated using the measured groundwater elevation data and the surveyed well casing elevations.
The survey data and groundwater level measurements are included in Table 1.
The groundwater gradient observed on September 9, 1998 ranged from 0.02 to 0.03 feet per foot (ft/ft)
to the southwest. Depth to water ranged from 39.96 feet below grade in well MW4 to 45.10 feet below
grade in well MW2.
A site map displaying [he location of the monitor wells is included as Figure 2. Groundwater samples were
obtained and submitted for laboratory analysis from one monitor well (MWS). Monitor wells MW 1, MW2,
MW3 and MW4 have been excluded from quarterly sampling and were not sampled. However, samples
are obtained from monitor well MWl and placed on hold in the event that the results of the samples
obtained from monitor well MWS report results in excess of permit requirements.
The sample was analyzed for benzene, toluene, e[hylbenzene, and xylenes (BTEX) using EPA Method 602,
and total dissolved solids (TDS) using EPA Method 160.1. Standards are presented in Tables 4 and 5.
The sample was also analyzed for Human Health Standards (total coliform, barium, fluoride, lead, and
nitrate+nitrite), Secondary Drittking Water Standards (chloride, iron, manganese, pH, and zinc) listed in
the Colorado Department of Health, Water Quality Control Commission, The Basic Standards for Ground
Water and for pesticides using EPA Method 608 and herbicides using EPA Method 8150. Standards are
presented in Tables 2 and 3. In addition, all monitoring wells were measured for depth to water to
deterntine the groundwater gradient and Flow direction.
Prior to sampling, monitor well MWS was purged of a minimum of three well volumes of water or until
the well was dry and allowed to recharge. On-site measurements of electric conductivity, pH, and
temperature were recorded to ensure that the well stabilized so that a representative sample of the aquifer
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