WSP06318

• File Number: 8045
• Description: Section D General Studies - Federal Projects - General
• State: CO
• Basin: Statewide
• Date: 12/1/1981
• Author: DOI-BOR
• Title: Front Range Unit - Coal Creek Water Studies - Colorado - Concluding Report
• Water Supply Pro - Doc Type: Report/Study

Marshall landfill included toluene; 1, I-dichloroethylene; trichloro-
fluoromethane; dichlorodifluoromethane; tetrachloroethylene; trichlo-
roethylene; 1, 2-trans-dichloroethylene; phenol; diethyl phthalate;
di-n-butyl phthalate; arsenic; cadmium; chromium; copper; lead;
selenium; and zinc. Aluminum, barium, and iron were also measured in
these surface water samples (personal communication with Tom Crowe of
Fred C. Hart Associates, Inc., March 19811. Elevated iron and manganese
concentrations have been measured in the ground water on the north side
of the landfill, and barium in Community Ditch, north of the landfill,
was approximately 8 times higher downstream of the Coal Creek Reservoir
site than in the upstream control (EPA letter, March 20, 1980).

Contours of piezometric surfaces indicate ground water might flow to the
southeast from the 1 andfi 11 towa rd the proposed Coal Creek Reservoi r
(see figure 2). With the possibility that leachates could contaminate
the ground water, and in turn, water in the proposed reservoir, a
monitor well drilling program was initiated to determine the direction
of ground-water movement in relation to the landfill, and to ascertain
if the ground water south of the landfill had been contaminated.
The wells were to be located at the positions in figure 2. Ground-
water monitoring well data are presented in table 4. To date, only
three of the proposed fi ve well s have been drill ed, precl udi ng deter-
mi nati on of the ground-water flow di recti on. The three well s have not
been suffiCiently developed to obtain water quality samples.

Table 4.--Ground-water monitoring well data

Hole No:

Schedul ed
depth (ft)

Estimated depth
to water table (ft)

Estimated depth
to Laramie-Fox Hills
aquifer (ft)

OW-2
OW-3
PZ-l
PZ-2
PZ-3

gO
70
455
435
400

50
50

330
285
275

Information from these three wells, correlated with water levels from
core holes drilled in the dam axis, suggested that the water table
generally follows the surface topography on the north side of the
reservoir area. It does not intercept the ground surface on the
valley's north wall or Coal Creek, as the creek is a losing stream
within that reach. Therefore, the ground water would not, at this time,
seep into the filled reservoir, even though it appears to be moving in
the direction shown in figure 2.

At some time a fter the fi 11 i no of the reservoi r, the unsaturated zone
between the ground surface and the water tabl e woul d become saturated

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