WSP07117

• File Number: 8276.130
• Description: Grand Valley Unit-Colorado River Basin Salinity Control Project
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 11/1/1990
• Title: Final Environmental Assessment: Price and Stubb Ditch Improvements - Grand Valley Unit
• Water Supply Pro - Doc Type: EIS

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CHAPTER II I
AFFECTED ENVIRONMENT AND ENVIRONMENTAL CONSEQUENCES

General Description of the Area

The proposed project araa is located at the eastern end of the Grand Valley
in Mesa County, in west-central Colorado. The Bookcliffs bound the study
area to the north and the Colorado River at the base of the Grand Mesa
forms the southeastern boundary. The communities nearest the proposed
project area are Palisade and Clifton, with Grand Junction located just
west of the study area. Mesa County's population is approximately 86,140,
with Grand Junction being the largest urban center. Agribusiness generates
39 to 51 million dollars annually within the county with peaches, apples,
pears, and cherries as major crops. Grand Junction, located at the
confluence of the Colorado and Gunnison Rivers, has an official elevation
of 4,586 feet; the lowest elevation in Mesa County is 4,300 feet where the
Colorado River enters Utah, and the highest point is Leon Peak at an
elevation 11,236 feet. The average year-round temperature is 52 degrees
Fahrenheit (0); January is the coldest month with an average temperature of
17.40, and July is the warmest month with an average 80.60. Average annual
precipitation at Grand Junction is less than 9 inches.

The Grand Valley is located at the extreme eastern extension of the Great
Basin Desert. Both the climate and geology of the region have a definite
influence on soil and soil moisture properties, and ultimately the native
and cultivated plant communities supported. Much of the area is underlain
with Mancos Shale from marine sedimentary formations. The soil derived
from weathered shale and ground-water percolating through the upper layers
of the parent shale are quite saline. Salinity is derived from the salts
of gypsum, sodium, potassium, magnesium, calcium, and carbonate.

Construction and management of irrigation systems and subsequent
residential development in the Grand Valley have altered native plant and
animal communities that historically occupied the proposed project area.
Based on vegetation, six distinct habitat categories occur in the Grand
Valley: river woodland, phreatophyic shrub, marsh, agricultural lands,
desert shrub, and pinyon-juniper woodlands (Ecology Consultants,
Incorporated, 1976). Within the proposed project area, phreatophyic shrub,
marsh, agricultural lands, and desert shrub comprise the habitats of
interest.

Both the Price and Stubb Ditches originate at the outlet of Tunnel No. 3 at
the upper end of the Grand Valley, and carry water from the Government
Highline Canal on a westward course below and roughly parallel to 1-70.
The Stubb Ditch is located near or adjacent to the Interstate, but the area
between the Stubb and Price Ditches has experienced the same residential
development common over much of the eastern end of the Grand Valley. The
Price Ditch is basically surrounded by residential development, is lined in
several places, and supports little in the way of vegetation that could be
used as wildlife habitat. Some residential development occurs south of
Stubb Ditch, but at present, land north of the ditch is basically
undeveloped and resembles the salt-shrub desert north of 1-70.

At present, the environmental values provided by the Price and Stubb
Ditches center around esthetics and recreation. The presence of the
ditches in the midst of developed farmlands and residential developments
provides an element of diversity. Residents use both ditches for
unauthorized recreational activities such as bicycling and horseback
riding, running, and walking. Vegetation within the ditch rights-of-ways
is limited, thus limiting wildlife habitat potential. There is no fishery
in the ditches.

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