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###### Department of Agriculture

###### Natural Resource Conservation Service

## Introduction

The plan/environmental assessment was developed under the authority of the Soil Conservation and Domestic Allotment Act of 1936. Funding for implementation is expected to be provided under the Federal Improvement and Reform Act of 1996, Public Law 104-127, as amended; Food Security Act of 1985, Subtitle D, Title XII, 16 U.S.C. 3830 et seq. An environmental evaluation was undertaken in conjunction with the development of the watershed plan. This evaluation was conducted in consultation with local, State and Federal agencies as well as with interested organizations and individuals. Copies of the Plan/Environmental may be obtained by contacting Allen Green, Colorado State Conservationist at the following address. Data developed during the environmental evaluation is available for public review at the following location as well: U.S. Department of Agriculture, Natural Resource Conservation Service, 655 Parfet St., Lakewood, Colorado 80215-5517.

## Background

The Silt unit was not identified by name in Title II of the Colorado River Basin Salinity Control Act, but was identified by USDA as an area which should be studied for possible salinity control.

The combined environmental assessment has three major components: (1) To determine the contribution of salt loading from the irrigated farmland; (2) to determine the opportunity for USDA to reduce salt loading through improvements in irrigation delivery and application systems; (3) to determine environmental effects of the proposed action.

Approximately 7,430 acres can be irrigated in the Silt Unit by five irrigation ditches. One of the aspects of the environmental evaluation involved inventorying and analyzing current irrigation systems and management practices. Data was analyzed on the five irrigation ditch systems. Each of the systems was analyzed to determine what types of improvements are needed. The remaining ditches were not studied because they are small or no longer in use.

The Wasatch Formation, a claystone shale marine formation with a very high salt content, underlies much of the valley and is the principal source of salt contributed to the Colorado River. Lenses of crystaline salt often are exposed during excavation into shale. Because of the arid climate, salts have not been leached naturally and applying excess irrigation water to the soil greatly accelerates the leaching process.

The Silt Unit contributes approximately 24,700 tons of salt annually to the Colorado River based on the 17-year USGS record of volume and concentration of outflow, minus volume and concentration of inflow. The 17-year record spans a good representation of dry and wet years. Approximately 14,030 tons come from irrigation practices, and is in the middle of the range of values used for the seven salinity project areas e.g. Grand Valley, Colorado; Lower Gunnison, Colorado; Mancos Valley, Colorado; McElmo Creek, Colorado; Uinta Basin, Utah; Price-San Rafael, Utah; and Big Sandy River, Wyoming. The remaining 10,670 tons represents salt produced from natural sources. Salt loading estimates include approximately 4,160 tons from ditch seepage and approximately 9,870 tons from on-farm deep percolation of irrigation water.

The proposed alternative plan contains structural and management improvements to irrigation systems which will in turn reduce salt loading to the Colorado River by 3,990 tons.

## Consultation-Public Participation

                    The Bookcliff Conservation District led the public participation process, which included several Public meetings. Public involvement primarily consisted of meetings; however, local newspapers were used to publicize the project. Several State and Federal agencies were consulted during project plan development.                          ( print page 69733)    

## Proposed Action

The proposed action will result in reducing seepage from the lateral ditches and increasing the irrigation efficiency to reduce deep percolation on 2,800 acres.

This action will consist of piping or concrete lining 45,000 linear feet of earthen irrigation ditches. On-farm irrigation improvements would consist of improved surface application systems and sprinkler irrigation.

The estimated total construction cost for the pipeline and sprinkler systems is $3,546,000. The total estimated project cost is $4,964,400. It is recommended that the federal cost-share used to implement the plan not be greater than 75 percent. A cost effectiveness analysis was used to determine the annual cost per ton of salt reduction.

## Basic Conclusions

The conservation treatment associated with the proposed action will not change the air quality or potable water quality of the area. The project will not create any new hazards to the transportation network within the effected project area. For these reasons it is felt that the public health and safety conditions of the effected area will not be significantly impacted.

There are no known unique geographic features in the project area that could be impacted by the proposed action.

During the inter-agency review process of the project plan no highly controversial effects were identified.

Past experience with similar projects in the area provide a high degree of confidence in the predicted impacts of the proposed actions.

This project is not unusual in nature and is quite similar to a project currently being implemented in Mesa County. For this reason we feel confident that no precedents are being set with this project.

No significant individual or cumulative effects to the human environment are expected when considering the context and intensity of the proposed action.

Our project investigations did not identify any cultural resource sites currently listed on the National List of Historic Places. In light of this, the proposed action will not impact any such sites.

Threatened and endangered species habitats do exist within the project boundaries. The proposed treatment will not change the extent or composition of this habitat therefore no impact is anticipated.

Communications with State and Federal natural resource management agencies did not reveal any violations of any laws, including the National Environmental Policy Act.

Many of the wetlands in the project area are “irrigation induced.” A minimal number of these acres would be impacted. Wetland functions for the majority of these are already impacted by the land use associated with them. The distribution and size of these wetlands is not likely to change.

The water quality of the Colorado River will be enhanced due to a reduction in salt loading from agriculture.

The agricultural producers participating in the project will benefit from the labor savings associated with implementation of improved on-farm irrigation application systems.

## Ultimate Conclusion

I find that the proposed action is not a major Federal action significantly affecting the quality of the human environment.

Dennis Alexander, 

Assistant State Conservationist-Programs.

[FR Doc. 05-22809 Filed 11-16-05; 8:45 am]

BILLING CODE 3410-16-P