DWR_2882817

• Title: GROUND WATER LEVELS IN THE DENVER BASIN BEDROCK AQUIFERS
• Year: 2003
• Document Type - Publications and Reports: Ground Water Levels Report

DENVER AQUIFER
The Denver aquifer consists of a series of interbedded clay shale, clay, claystone, siltstone and
sandstone lenses. Carbonaceous material and coal beds are common within the hydrogeologic unit. The
aquifer underlies an area of approximately 3,500 miles and varies in thickness from a feather edge up to
1,000 feet. Distinctive characteristics of the a.quifer are the fine-grained nature vf the material composing
the aquifer and sandstone lenses of limited areal extent.
Although the aquifer is utilized extensively for domestic water supplies, relatively iow well yields
�generally 20-to-50 gallons per minute (gpm}} limit its use primarily to individual residential wells;
however, a number of municipal wells have been developed with yields up tv 100 gpm. The higher yield
wells are not indicati�e of the aquifer's potential in most areas.
The Den�er aquifer is separated from the underlying Arapahoe aquifer by an extensi�e clay shale
unit approximately 50 feet thick. The clay sha�e interval serves as a hydraulic barrier between the aquifers.
ARAPAHUE AQUIFER
The Arapahoe aquifer is composed of interbedded conglomerates, sandstones, siltstones, and clay
shales. The aquifer underlies an area of almost 4,70D square miles and is generally about 44U feet thick.
The northern portion of the hydrogeologic unii can be subdivided into an upper and lower aquifer that is
separated by a shale sequence ranging from 5�-to-100 feet thick.
High capacity we11s (300+ gpm) are common in the Arapahve, and the aquifer is used extensively to
supply municipal water systems. Water quality is generally good in the aquifer as evidenced by its use by
Deep Rock Water to obtain water for bottling.
LARAMIE FURMATION
The major part of the Laramie Formativn forms the aquatard or hydraulic bamer that separates the
Arapahoe aquifer from the underlying Laramie-Fvx Hills aquifer. The formation consists of approximately
400 feet of clay shales with minor interbeds of sandstone and siltstone. Coal beds are common within the
fvrmation and have been mined commercially along the eastem margin of the basin. Minor amounts of
water are present within the sandstones, but are rarely developed for water supplies. Water in the sandstone
units is of generally poor quality due to the presence of sulfides and biogenic gas.
The basal portion of the Laramie Formation contains two relatively thick sandstone uni#s (the A and
B sandstones) which are hydraulically isolated from the upper part of the formation. These sandstone units,
combined with the underlying Fox Hills Sandstone compose the hydrogeologic unit of the Laramie-Fox
Hills aquifer.
LARAMIE-F4X HILLS AQUIFER
The lowermost of the four Denver Basin aquifers is the Laramie-Fox Hills aqu�fer which underlies
approximately 6,700 square miles and marks the areal extent of the basin for economic ground water
de�elopment. The Laramie-Fox Hi11s aquifer is generally between 250 feet and 34� feet thick, which
4