01-22973. Casper Creek Crossing, Spence-Thermopolis 230-kV and Alcova-Copper Mountain 115-kV Transmission Lines

AGENCY:

Western Area Power Administration, DOE.

ACTION:

Notice of Floodplain Statement of Findings.

SUMMARY:

This Floodplain Statement of Findings for the Casper Creek Crossing, Spence-Thermopolis 230-kilovolt (kV) and Alcova-Copper Mountain 115-kV Transmission Lines was prepared in accordance with the U.S. Department of Energy's (DOE) Floodplain/Wetland Review Requirements (10 CFR part 1022). Western Area Power Administration (Western), a power marketing agency of the U.S. Department of Energy (DOE), is the lead Federal agency for a proposal to make repairs and correct erosion problems at the Casper Creek Crossing for the Spence-Thermopolis 230-kV and Alcova-Copper Mountain 115-kV Transmission Lines. This project is located in Natrona County, Wyoming, approximately 40 miles west of Casper, Wyoming. Western plans to replace an existing culvert crossing at the Casper Creek with a rock filled gabion type structure. Approximately 50 yards downstream, additional rock filled gabion type structures will be placed in the creek. A crossing at Casper Creek is necessary to provide access for transmission line inspection and transmission line maintenance. All proposed work will occur within the floodplain of the Middle Fork Casper Creek.

Western prepared a floodplain assessment describing the effects, alternatives, and measures designed to avoid or minimize potential harm to or within the affected floodplain. This action is categorically excluded under DOE's National Environmental Policy Act (NEPA) Implementing Procedures (10 CFR part 1021). A 15-day public review period will be provided before the action is taken.

DATES:

Comments on the floodplain action are due September 28, 2001.

ADDRESSES:

Comments should be sent to Mr. Rodney Jones, Environmental Specialist, Rocky Mountain Customer Service Region, Western Area Power Administration, P.O. Box 3700, Loveland, CO 80539-3003; fax: [phone], e-mail [e-mail].

FOR FURTHER INFORMATION CONTACT:

Mr. Rodney Jones, at the above address, telephone [phone]. For further information on DOE Floodplain/Wetlands Environmental Review Requirements, contact: Ms. Carol M. Borgstrom, Director, NEPA Policy and Compliance, EH-42, U.S. Department of Energy, 1000 Independence Avenue SW., Washington, DC 20585, telephone [phone] or [phone].

SUPPLEMENTARY INFORMATION:

This Statement of Findings for the proposal to make repairs and correct erosion problems at the Casper Creek Crossing for the Spence-Thermopolis 230-kV and Alcova-Copper Mountain 115-kV Transmission Lines was prepared in accordance with 10 CFR part 1022. A notice of floodplain involvement was published in the Federal Register (FR) on June 25, 2001 (66 FR 33678). The State of Wyoming, Office of Federal Land Policy, responded to the notice stating that no State agencies brought up concerns to be addressed in the floodplain assessment. The State of Wyoming requested a copy of the floodplain assessment when it was completed.

The Casper Creek Crossing is located at the Middle Fork Casper Creek, in Natrona County, Wyoming, in T.3 N., R. 86 W., Sections 3 and 4. The road used to access and maintain Western's Spence-Thermopolis 230-kV and Alcova-Copper Mountain 115-kV Transmission Lines has been washed out by flows within the Middle Fork Casper Creek. Since construction of the power lines, the culverts at the stream crossings have been washed out and replaced numerous times. After each wash out, it was necessary to move the stream crossings further upstream to avoid the deeply incised stream channel. The proposed project would construct drop structures and a stream crossing that are designed to stabilize the stream channel, dissipate stream flow velocities during peak flow events, minimize erosion, restore stream banks to reasonable slopes, and allow continued access by Western to inspect and maintain its transmission lines.

Drop structures would be placed at two locations on the Middle Fork Casper Creek. The uppermost location will be approximately 350 feet west (upstream) of the transmission line's rights-of-way. A series of three drop structures is anticipated at the uppermost location. The low water crossing, consisting of riprap, will be located immediately upstream of first drop structure. Drop structures will also be placed at or near the original road crossing (downstream) directly below the existing power lines. A series of four drop structures is anticipated at the downstream location.

The drop structures will be constructed of one-quarter inch thick steel plate, rock riprap, gabion wire, silt liner, and steel pipe. Additionally, riprap will be placed upstream and downstream of the drop structures to provide grade stabilization upstream and downstream of the drop structures. The stream banks between the upper and lower drop structures will be contoured and vegetated. Slopes along this stream reach will be cut back to a 2 to 1 slope ratio (2:1) or less. Upon completing the bank contouring, the slopes will be seeded with native vegetation to promote slope stability.

Western considered an alternative to the proposed project that would involve reinstallation of larger culverts at the present crossing site. However, given the past experience with culverts washing out during heavy rain events, this was not considered a long-term solution to the problem. Repeated culvert washouts were contributing to stream bank erosion and stream channel degradation downstream.

Environmental impacts associated with the proposed project are expected to be minimal. Based on the hydrology of the Middle Fork Casper Creek and apparent lack of hydrophytic vegetation and hydric soils, wetlands are not present at the site. Implementation of the proposed project will stabilize the stream channel, dissipate stream flow velocities, stabilize stream banks, and maintain the chemical, physical, and biological integrity of the Middle Fork Casper Creek. Direct and indirect impacts to other resources (e.g., wildlife and air quality) are expected to be negligible as well.

The project is located within the boundaries of a National Register of Historic Places-eligible archaeological site. Through a conversation between the Western Historic Preservation Officer and the Wyoming State Historic Preservation Office (SHPO), Western contracted to perform archaeological testing to determine if this project will have an effect on the eligibility of the site. A field visit indicated that it is unlikely intact buried features are located in the project area. An extensive augering program will be done within the area to be impacted along the creek, as well as along the access road to the east. Western will consult with the SHPO on the findings of this augering program prior to implementation of the project.

The construction of the project would not affect existing flood characteristics. No measurable change in flood stage is anticipated. Construction activities, which will take approximately 14 days to complete, will be scheduled during late summer to early fall, under low flow conditions. The action conforms to all applicable State and local floodplain protection standards.

A small increased risk of pollution could result from having construction equipment working in the floodplain. This includes the risk of accidental oil or fuel spills from malfunctioning equipment. Given the size of equipment involved and the amount of potential spill material, this risk is considered very low. If a spill were to occur it would be minor and could be readily contained and cleaned up.

Dated: September 5, 2001.

Michael S. Hacskaylo,

Administrator.