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TABLE OF CONTENTS
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Letter of Transmittal
Table of Contents
S cope
S ite Investigation
Geology
- Regional and Local Setting
Economic Geology
Potential Geologic Hazards
Groundwater Resources
Sewage Disposal
Summary, Conclusions, and Recommendations
Site Area Geology
Page
ii
1
1
1,2
1,2
2,3
3
4
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4
Drawing No. 1
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SCOPE,,
This:: report presents geologic data, ,interpretation, and
evaluation: which, pertains to the development of the proposed.
Prairie View Estates in Weld County,___ Colorado. Prairie View
Estates • is- `.a proposed 68 -acre development located on a tract of
land located north of the Town of Windsor. More particularly, the
site is located in the Southeast:: Quarter. (SE 4) of Section 4,
Township' -6 North, Range 67 West of the 6th P.M., Weld County,
Colorado.
The intent of this subdivision is to provide lots for
residential development.
SITE INVESTIGATION
This investigation was carried out by means of site inspection
by the author of this report, evaluation of test hole data from
Foundation .and _Soils ,Engineering, Inc., Project No. 1413-01-01,
whichwas froma; tract of land northwest of the proposed site, and
information obtained from "Sand, Gravel, and Quarry Aggregate
Resources - Colorado Front Range Counties", "Guidelines and
Criteria for Identification and Land -Use Controls of Geologic
Hazard and Mineral Resource Areas" and "Proceedings of the
Fifteenth Forum on Geology of Industrial Minerals" by the Colorado
Geological Survey, "Geologic Map of Colorado" by the U.S.G.S. and
"Soil Survey of Weld County Area, Colorado", by the U.S.D.A. Soil
Conservation Service. Information of economic constraints for sand
and gravel mining were from verbal communications with local gravel
pit operators.
GEOLOGY
N
Regional and Local Setting
The site lies in the Colorado Piedmont Section of the
Great Plains Physiographic Province. The Colorado Piedmont is
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an elongated trough in the Great Plains, adjacent. to the Front
Range ;., of .the ;Southern Rockies. The.j Colorado- vPiedmont was
formed when uplift of the area in Miocene -Eocene times (20-50
million years, ago) produced an increase of stream erosion
resulting -in, scouring next to the foothills and outlying
areas. The Piedmont is bordered by tale Southern Rockies to
the;awest, Great Plains escarpment to2 the northeast, and Palmer
Divide to -the south.
More particularly, the site lies between the Town of
Windsor, Weld County, Colorado, and Thompson Lake.
.Structurally, the site lies on the western edge of the
Denver; Basin, a thick accumulation of sediments involved with
downwarping in the basin area and uplift of the adjacent
highland areas in late Cretaceous and early Cenozoic. Small
anticlinalfolds occur adjacent to the Front Range in the
_sedimentary rocks and are conducive to the accumulation of oil
and gas deposits. .The - closest . know faults to the site are the
:Thompson Canyon Fault and Nilner::Mountain Fault, which are
approximately 14 miles to the west. Both faults are believed
to be inactive since no recent records of fault movement or
earthquakes exist.
Slopes at the site are predominantly slight with drainage
flowing to the south with a maximum slope of approximately
three percent (3%). The site is not located within the 100
year or 500 -year floodplain. Groundwater levels are expected
to be at a depth of approximately ten feet (10').
Economic Geology
Mineral resources at the site are not anticipated. Test
hole data reveals that no pitrun was encountered in the area.
Therefore, the minable area of the site was determined to be
0 acres. Based on the above data and criteria used in
determining economic feasibility of local gravel operations,
we feel that the site is not large enough and does not contain
enough gravel to be economic for mining. Information on oil
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and gasdeposits at the site were not available at this time;
however, foil and gas "_wells are located near; this area.
Potential Geologic Hazards
Geologic hazards caused by gravity, such as landslides,
rockfall, 'mud :anddebris flows, and snow avalanches, are not
anticipated -in the present state of the '?site. Utility
trenches"may{:require shoring or bracing in order to create
safe;_ working: conditions during construction.
The: SCS described the soils at the site as1) Kim loam,
2)Otero Sandy loam, and 3) Thedalund loam. These soils are
described by the SCS as having 1 to 3%, 3-5%, and 1 to 9%
slopes, respectively. The Thedalund loam is the only soil
with limited cropping..
The soils, which are to support foundations, are suitable
to support the foundation loads. Each building site should
have. a.°.complete geotechnical investigation and engineered
,foundation so as to: minimize the effects of structures. on the
sandy clay soils.
GROUNDWATER RESOURCES
Potable water is to be supplied by the North Weld County Water
District. Shallow groundwater at the site should not be used as
potable water, but may be used for irrigationwater pending
acceptable water tests and well permits. Pollution of the
groundwater caused by individual sewage disposal systems at the
site should -not exist due to the systems being designed and
installed per the I.S.D.S.R. for Weld County.
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SEWAGE DISPOSAL
Sewage disposal on the site will be disposed using septic
fields designed and installed per the I.S.D.S.R. for Weld County.
4.
SUMMARY, CONCLUSIONS, AND RECOMMENDATIONS
The site appears not to be underlain with. pit run, and,
therefore, is not suitable for mining. Oil and gas wells are
located in the region although sufficient information was not
obtainable to determine the economic feasibility for oil and gas
production at the site._ Groundwater depth, potentially expansive
soils, and potentialtrench caving are hazards which will require
attention prior to and during the construction process.
Potential hazards can be minimized or eliminated by 1) a
geotechnical .investigation being performed for each site or the
subdivision and following the recommendations in the report, and 2)
following current construction codes and practices.
Based on the data mentioned in this report, we feel that the
site is suitable for the proposed Prairie View Estates provided the
recommendations in this report are met. This report does not
reflect any variations in surface and subsurface conditions either
natural or man-made.
971232
KRAIR►E VIEW ESTATES
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