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ENGINEERING GEOLOGY REPORT FOR
PROPOSED PRAIRIE RIDGE ESTATES
NE 1/4 OF SECTION 8,
TOWNSHIP 7 NORTH, RANGE 67 WEST OF THE 6TH P.M.
WELD COUNTY, COLORADO
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Prepared for:
MR. GEORGE CARLSON
C/O TEAM ENGINEERING, ATTN: JEFF COUCH
3468 SHALLOW POND ROAD
FORT COLLINS, COLORADO 80528
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DECEMBER 9, 2003
JOB NO. 03-1001
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THOMAS W. FINLEY
CONSULTING GEOLOGIST
P.O. BOX 7676
LOVELAND, COLORADO 80537
2005-0564
Engineering Geology Report
Job No. 03-1001
Page 5
building foundations, roadways and onsite wastewater systems (OWS).
FOi TNDATIONS• The upper soils exhibit low swelling in some areas and a slight collapse potential
in other areas. Soil movement, such as collapse or swelling, can impose pressures to building
foundations and other structures if the structure is not properly engineered. Engineered spread footing
! foundations are appropriate where slight collapse or low swell potentials are encountered. Drilled
pier, caisson, foundations may be necessary where potentially swelling rock exists within foundation
influence zones. High bearing loads may supported by the rock when located at reasonable depths.
The presence of ground water may require special methods for placement of concrete in the caisson
borings. Fluctuating ground water levels may be greatest near the Cactus Hill Lateral. A site-specific
geotechnical investigation, which can be used to design the foundation, is recommended for each
' structure to determine soil strengths, swell potentials and groundwater levels. Excavations for
�. foundations, utilities and other structures may need to be protected from caving. Refer to OSHA
standards for the appropriate protection methods.
1 ROADWAYS' It is our understanding the interior roadway may be paved. A pavement design study
was being prepared in conjunction with this report. Laboratory tests and classifications indicate the
roadway subgrade soils have low plasticity and exhibits low to moderate subgrade support for paving.
One sample had a moderate swell potential whereas the remaining samples did not exhibit swelling.
Swell mitigation of the subgrade or more frequent maintenance of the pavement may be necessary for
part of the roadway. Low strength soils were observed primarily along the north end of the proposed
roadway. Low strength soils may be able to be improved by compaction methods, chemical
l' ' stabilization, soil replacement or geotextile design.
4, flitLCTIF. WASTEWATER SYSTEMS (OWS). No percolation tests were conducted as part of our
.n. SCS literature suggests slight limitations for septic systems for the most of the site
OH groups indicated on the map. Severe limitations due to shallow rock are described in the
Engineering Geology Report
Job No. 03-1001
Page 6
Thedalund loam mostly located near the Cactus Hill Lateral. The lot sizes proposed should provide
enough area to be selective in determining areas suitable for "standard"-type OWS on each lot.
Engineered OWS are may be required on some lots due to shallow rock and/or slow percolation.
Site-specific percolation investigations for OWS are required by the County Health Department prior
to issuance of a building permit.
CGRO1.OGJC HAZARDS• The site observations and hazard map did not indicate signs of geologic
hazards caused by gravity, such as landslides, debris flows, rock fall, or unstable or potentially
unstable slopes. Man-made activities could produce conditions, which may result in hazardous
conditions, if not carefully planned. No geologic hazard mitigation is anticipated for this site.
' CONCLUSION AND LIMITATIONS
Our study is to be used in aiding in the determination of the compatibility of geologic
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conditions and the proposed development. This report shall not be used for the design of structures or
OWS. This study was preliminary in nature and did not include an extensive exploration program for
the presence of oil, natural gas, uranium or other mineral resources. Based on existing maps, literature
and field data potential sand, gravel and quarry aggregate resources are not believed to exist in
economic quantities. Although no geologic hazards appear to exist in the present condition man-made
activities could result in conditions that could produce hazardous conditions. Site-specific
geotechnical and onsite wastewater investigations should be conducted for each lot to develop design
criteria.
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