SCOPING STATEMENT

Modification of Coolidge , A Feature of the San Carlos Irrigation Project.

Gila, Phial, and Graham County,

I. Background.

The Bureau of Reclamation (Reclamation) is preparing an Environmental Assessment (EA) to disclose the environmental consequences of modifying Coolidge Dam, a feature of the San Carlos Irrigation Project (SCIP). The Bureau of Indian Affairs (BIA) owns Coolidge Dam and the SCIP operates the dam. Coolidge Dam is located about 90 miles southeast of Phoenix, Arizona on the . San Carlos (Lake) is formed behind the dam. The dam delivers water downstream to irrigated lands of the Gila River Indian Community and to the San Carlos Irrigation and Drainage District.

The BIA has requested Reclamation's assistance in evaluating and documenting the potential safety problems of Coolidge Dam. Reclamation has agreed to be the lead agency for preparation of the EA. In 1980, a safety evaluation by Reclamation identified several safety deficiencies related to the dam's inability to pass the Probable Maximum Flood (PMF). The safety deficiencies that may lead to modification of Coolidge Dam are a hydrologic-structural problem and a tability problem.

1. Hydrologic-Structural problem and proposed modification:

Flood routing studies using the PMF indicate water could potentially overtop the dam by up to 21 feet. The existing spillways have insufficient capacity to route the PMF and are showing signs of deterioration as documented in the 1980 safety evaluation. The PMF would potentially overtop the dam, destroy the existing spillways, erode the right and left abutment, and result in failure of the dam. The modifications proposed for correcting the hydrologic-structural problem are to: 1) reconstruct the spillways, realigning them and making them wider and 2) constructing overtopping protection of concrete, two to three feet thick, on the downstream abutments of the dam from the dam crest to the riverbed.

2. Stability problem and proposed modification:

The left abutment of the dam is deteriorating and would fail during the Maximum Credible Earthquake (MCE) or under certain static loading conditions. The modifications proposed for correcting this problem are 1) concrete overlays on both the left and right abutment near the dam crest and 2) constructing bearing blocks and installing post-tensioned steel tendons in the left abutment to anchor the abutment.

3. Other considerations:

New gates will be proposed. The existing gates are inoperative and restrict the conservation space in the reservoir to elevation 2511. New gates would allow operation of the reservoir up to its authorized conservation elevation of 2523. A flood warning system to alert downstream individuals and communities would also be proposed. II. Significant Issues.

Reclamation is issuing this scoping statement to inform the public that an environmental document (the EA) is being prepared and ask for public input and involvement in preparation of the EA. Specifically, Reclamation would like your input regarding significant environmental issues that you believe should be addressed in the EA. Reclamation has tentatively identified these significant issues that could result from modification of Coolidge Dam:

1. Impacts on aquatic resources of both San Carlos Reservoir and the Gila River downstream of the dam.

2. Impacts on riparian habitat both around San Carlos Reservoir and downstream of the dam along the Gila River.

3. Impacts on threatened and endangered species, particularly the bald eagle and Arizona cliffrose.

4. Impacts on the historical significance of the dam itself, or on other cultural resources found both upstream and downstream of the darn.

5. Impacts on human safety.

6. Impacts on the social and economic condition of the San Carlos Apache Tribe and the Gila River Indian Community.

7. Impacts on existing and future recreation opportunities and activities both upstream and downstream of the dam.

8. Impacts on downstream water users of the San Carlos Irrigation Project, San Carlos Irrigation and Drainage District, and hydroelectric power generated by the dam.

111. Alternatives.

Reclamation will develop a range of reasonable alternatives to the proposed action of modifying the dam. A possible range of alternatives would be from taking "No Action" ,meaning no modifications will be made to the dam, to the proposed action to modify the dam to correct a of the known safety deficiencies. Other reasonable alternatives may be identified as a result of public input. What other alternatives should Reclamation consider?

IV. Participation.

Reclamation is the lead agency for preparation of the EA. The BIA is the cooperating agency. Reclamation will also involve other local, state, and federal agencies and Indian communities in preparation of the EA. An interdisciplinary team has been assembled to conduct the environmental analysis. It presently appears that the following specialized skills will be needed to conduct the environmental analysis:

Wildlife biologist Archaeologist Aquatic biologist design engineer Fisheries biologist Economist Hydrologist Safety engineer Recreation management V. Timing.

Oral and written comments on this proposal are welcome at any time. However, to be most useful to Reclamation in preparation of the EA, they should be received by April 20, 1988. Please direct comments to:

Bureau of Reclamation Arizona Projects Office Environmental Division P.O. Box 9980 Phoenix, Arizona 85068

Attention: Bruce Ellis or Dan Fritz Phone: (602) 870-6770 or 870-6776

Reclamation plans to complete the EA by September 30, 1988.