Floodplain Statement of Findings for the Replacement of Four Bridges on the Savannah River Site

DEPARTMENT OF ENERGY

Floodplain Statement of Findings for the Replacement of Four

Bridges on the Savannah River Site

AGENCY: Department of Energy (DOE).

ACTION: Floodplain Statement of Findings.

SUMMARY: This Floodplain Statement of Findings is prepared in

compliance with 10 CFR Part 1022. It is designed to evaluate the impact

to the floodplain of the Savannah River Site (SRS) resulting from work

that is needed to replace selected bridges on SRS Roads 8-1 and 2-1.

The scope of this project is intended to immediately replace three

bridges because of deteriorated, decayed, or rotten timber piles. A

fourth bridge would be scheduled for a later replacement. The proposed

work would involve working in and close to the 100-year floodplain of

Upper Three Runs and Tinker Creek. The creeks associated with these

projects have average annual flows which are greater than 5 cubic feet

per second and a Federal permit pursuant to Section 404 of the Clean

Water Act is not expected to be required for the proposed work. These

impacted areas would include:

Replacement of Bridge 603-13G at the intersection of

the stream Upper Three Runs Creek and SRS Road 8-1.

Replacement of Bridge 603-14G at the intersection of

the stream Tinker Creek and SRS Road 8-1.

Replacement of Bridge 603-15G at the intersection of

the stream Upper Three Runs Creek and SRS Road 2-1.

Replacement of Bridge 603-39G at the intersection of

the stream Tinker Creek and SRS Road 2-1.

DATE: Comments on this Statement of Findings are due on or before

September 15, 1994.

ADDRESSES: Comments should be addressed to Floodplain Comments, Stephen

R. Wright, Director, Environmental and Laboratory Programs Division,

U.S. Department of Energy, Savannah River Operations Office, P. O. Box

A, Aiken, South Carolina 29802. The phone number is (803) 725-3957. Fax

comments to: (803) 725-7688.

FOR FURTHER INFORMATION, PLEASE CONTACT: Ms. Carol M. Borgstrom,

Director, Office of NEPA Oversight (EH-25), U.S. Department of Energy,

1000 Independence Avenue, S.W., Washington, D.C. 20585, Telephone (202)

586-4600 or (800) 472-2756.

A location map showing the project sites and further information

can be obtained from the Savannah River Operations Office (See

ADDRESSES above).

SUPPLEMENTARY INFORMATION: The bridges on SRS Road 8-1 (603-13G and

603-14G) which cross Upper Three Runs Creek and Tinker Creek will be

replaced and raised with minimal short-term impact and no long-term

impact to floodplains. A storm water and sediment control plan will be

required prior to bridge replacement in order to minimize sediments

eroding into the adjacent floodplain.

The work required to replace these two bridges would be

accomplished from the existing road beds using a crane for pile

driving, erection, and demolition. This activity should not have any

significant impact on the floodplain. The only disturbance to the

stream is anticipated to be the installation of pilings to support the

center span of the bridge. Prestressed, precast concrete beams shall be

used to minimize pile installation in the stream by constructing longer

spans. A small amount of sediment would be expected to go into the

stream where the work is close to the channel and temporarily increase

stream's sediment load level. These increased sediment loads would be

less than that encountered after a heavy rain storm. The old bridge

supports would be cut off at the stream bed. The bridges are to be

replaced in kind at their present locations so that there should be no

loss or long term impact to floodplains.

The bridge (603-15G) that spans Upper Three Runs Creek on SRS Road

2-1 would be replaced with minimal short-term impact and no long-term

impact to wetlands or floodplains. The bridge (603-39G) that spans

Tinker Creek on SRS Road 2-1 would be scheduled for replacement in the

future as funding became available.

The conditions of the bridges covered in this Statement of Findings

do not meet Department of Energy, American Association of State Highway

and Transportation Officials, South Carolina Department of

Transportation, or Federal Highway Administration standards and

guidelines and therefore severely limits the type of traffic that may

utilize these bridges on the primary route to the Advanced Tactical

Training Area. Fire control equipment and logging trucks use this route

so that any delay in replacing these bridges would greatly limit the

traffic count and load limits permitted along this route, and would

constitute a safety hazard to SRS personnel. Repair was considered as a

potential alternative but with the present condition of the bridges,

the most cost effective method is replacement. The environmental impact

of repairing these bridges was also evaluated and found to be nearly

identical in scope to that of replacing the bridges. Bridge

rehabilitation strategies were evaluated and concluded replacement of

the bridges over rehabilitation for many reasons, but largely because

replacement of deteriorated piles and backwalls would fail to improve

the load carrying capacity of the bridges for vehicles crossing the

structure. Timber pile and backwall replacement will cause the same

environmental impacts if not, more, because the bridge deck and piling

caps must be completely removed in order to drive new piles and

construct concrete abutments at the edge of the stream in order to

maintain existing span lengths. Replacement of the entire bridge

structure allows the span to be lengthened sufficiently to permit

construction of bridge abutments well away from the stream bed, thereby

reducing impacts, and reducing construction costs.

Several mitigation activities will be implemented to minimize

potential impacts to the floodplain. Silt fences and other erosion

control structures as needed will be installed to ensure there is no

deposition in downslope areas. Long-term construction impacts in the

floodplain and wetland areas will be minimized through the removal of

any excess excavated sidefill and restoration to the original contours

following completion of construction. An erosion control plan will be

developed so that the proposed action complies with applicable State

and local floodplain protection standards and further, to ensure that

no additional impacts will occur due to erosion and sedimentation. Best

management practices will be employed during construction and

maintenance activities associated with this proposed action.

Issued in Washington, D.C., on this 25th day of August, 1994.

Donald F. Knuth,

Acting Deputy Assistant Secretary for Facility Transition and Technical

Support, Defense Programs.

[FR Doc. 94-21541 Filed 8-30-94; 8:45 am]

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