HYDRO20522

• Permit No: M1980233
• IBM Index Class Name: Hydrology
• Doc Date: 4/4/1996
• Doc Name: COSTILLA LANDFILL PIT COSTILLA CNTY COLO
• From: GREYSTONE
• To: DMG
• Media Type: D
• Archive: No

iii iuiiiiiiiiii iii
April 3, 1996
~~
~~
Mr. James C. Stevens
State of Colorado
Division of Minerals and Geology
Department of Natural Resource
1313 Sherman St., Room 215
Denver, CO 80203
Re: Costilla Landfill Pit, Costilla County, Colorado
Dear Mr. Stevens:
RFr,FIVFp
APR 4 4 1996
iy~ °~
olwsbn of Mrnerais 8 Geology
Greystone is submitting [his letter on behalf of Costilla County to provide you with data collected
during the recent field activities in March 1996 for the above referenced site. The analytical results
for the groundwater samples collected from the monitor wells will be submitted by April 17, 1996.
A regional site map is provided as Figure 1. A site map displaying [he location of the four monitor
wells is provided as Figure 2. A groundwater elevation map is included as Figure 3. Survey data,
depth to water, and total depth of the monitor wells is provided in Table 1. Soil descriptions and
well completion logs aze attached.
All monitor wells were surveyed on March 21, 1996, using an arbitrary benchmark established
onsite. Depth to water was measured from the top, north side of the well casing on the sante day.
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. A groundwater elevation contour map is included as Figure 2.
The groundwater gradient observed on March 21, 1996, ranged from 0.003 to 0.03 feet per foot (ft/fr)
to the southwest. Depth to water ranged from 36.00 ft below grade in well MW4 to 46.60 ft below
grade in well MW2.
The drilling commenced on March 13, 1996, and was completed on March 16, 1996. Four monitor
wells were installed on the site (Figure 2) using on ODEX air rotary drill rig utilizing an 8.375
outside diameter (OD) continuous flight auger.
During drilling of borehole MW1 through MW4, soils were monitored for the presence of
hydrocarbon vapors using a Thermo Environmental Instruments Model 580B organic vapor monitor
(OVM) photo-ionization detection meter (PID) calibrated to an isobutylene standard. Soil sampling
depths, PID readings, and lithologic descriptions for the boreholes are included on the lithologic and
well completion logs are attached.
5990 Greenwood Plaza Blvd. Suite 250 Englewood, CO 80111
[phone] Fax[phone]