Floodplain and Wetlands Involvement Notification for the A-01 Outfall Constructed Wetlands Project at the Savannah River Site (SRS)

DEPARTMENT OF ENERGY

Floodplain and Wetlands Involvement Notification for the A-01

Outfall Constructed Wetlands Project at the Savannah River Site (SRS)

AGENCY: Department of Energy (DOE).

ACTION: Notice of floodplain and wetlands involvement.

-----------------------------------------------------------------------

SUMMARY: DOE proposes to construct and operate an artificial wetlands

to treat effluent from the A-01 outfall located on SRS. The A-01

effluent has consistently not met proposed outfall limits which will

become effective on October 1, 1999. DOE needs to reduce the copper and

chronic toxicity levels in the effluent to ensure compliance when these

proposed outfall limits go into effect. It has been determined that a

subsurface flow wetlands and an associated detention basin would

adequately treat the effluent to meet the new discharge limits. As part

of the proposed project activities, a new outfall structure would be

constructed within the 100-year floodplain and wetlands associated with

Tim's Branch, the headwaters stream into which the treated effluent

would be discharged. These activities would necessitate temporary

construction access, construction of the new outfall structure, and

placement of riprap material in this drainage corridor. In accordance

with title 10 CFR part 1022, DOE will prepare a floodplain and wetlands

assessment and will perform this proposed action in a manner so as to

avoid or minimize potential harm to or within the affected floodplain

or wetlands.

DATES: Comments on the proposed action due on or before March 18, 1998.

ADDRESSES: Comments regarding this assessment should be addressed to

Andrew R. Grainger, National Environmental Policy Act (NEPA) Compliance

Officer, Savannah River Operations Office, Building 773-42A, Room 212,

Aiken, South Carolina 29808. The fax/phone number is (800) 881-7292.

The e-mail address is [email protected].

FOR FURTHER INFORMATION ON GENERAL FLOODPLAIN/WETLANDS ENVIRONMENTAL

REVIEW REQUIREMENTS, CONTACT: Ms. Carol M. Borgstrom, Director, Office

of NEPA Policy and Assistance (EH-42), U. S. Department of Energy, 1000

Independence Avenue, SW., Washington, DC 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

[[Page 10368]]

Operations Office (see ADDRESSES above).

SUPPLEMENTARY INFORMATION: The recent issuance of the revised National

Pollutant Discharge Elimination System (NPDES) permit for SRS by the

South Carolina Department of Health and Environmental Control (SCDHEC)

established new outfall limits for copper, lead, mercury, and chronic

toxicity which will become effective on October 1, 1999. Subsequent to

SCDHEC issuing the revised permit, samples taken at the A-01 outfall

have resulted in the effluent consistently not meeting the new 1999

outfall limits for copper and chronic toxicity. DOE needs to implement

actions to reduce these concentrations prior to that time when the new

outfall limits are scheduled to go into effect. Extensive research has

indicated that a constructed subsurface flow wetlands with an

associated detention basin would treat these constituents and reduce

the concentrations below the new permit limits before the effluent

reaches the NPDES compliance sampling point.

The proposed action entails the construction, and operation of the

following: (1) A system of pipes to collect the process and storm water

effluent from the local outfalls (i.e., A-01, A-03, A-04, A-05, and A-

06), (2) a subsurface flow wetlands/detention basin complex to treat

the effluent from these outfalls, and (3) an outfall system to

discharge the treated effluent into Tim's Branch, the previously-

established onsite receiving stream for the subject outfalls. The A-01

sampling point monitored by both SRS and SCDHEC would be relocated from

the current location to the new outfall structure prior to the effluent

flow entering the waters of the State.

Construction of the collection pipeline and subsurface flow

wetlands/detention basin complex would involve the siting and

implementation of these project components in upland areas above the

floodplain and wetlands areas associated with Tim's Branch. These

upland sites are currently occupied by either planted pine forest or

previously-developed area (e.g., graveled parking lots). The pine

forest, dominated by a mature overstory of longleaf pine (Pinus

palustris), has been managed by the U.S. Forest Service over the past

four decades for timber production purposes only. Best management

practices (e.g., placement of silt fences) would be employed during

construction activities associated with this portion of the proposed

action to ensure there is no deposition of erosional material or

sediment into the downslope wetland areas.

Construction of the new outfall discharging into Tim's Branch would

entail placement of an outflow pipe from the wetlands/basin complex,

construction of an outfall structure on the margin of the stream

channel, and placement of riprap within the streambed itself to prevent

erosion and scouring by the discharged effluent. The location of the

proposed new outfall would be on the south side of the Tim's Branch

stream corridor. The width of wetland area within that portion of the

stream corridor is approximately two to four meters. The stream channel

is deeply cut into the bottomland and the streambed is situated

approximately one to two meters below the grade of the surrounding

forest floor. These wetlands are characterized by a headwaters drainage

habitat dominated by an overstory of sweetgum (Liquidambar

styraciflua), water oak (Quercus nigra), and hickory (Carya spp.).

Hydrology is provided through effluent from the local NPDES outfalls

and storm water runoff from the surrounding higher elevation lands. The

soils within the stream channel appear to be largely erosional sediment

in composition. The project activities to be located immediately on the

south side of Tim's Branch and within the streambed itself are also

located within the 100-year floodplain. Proceeding with this proposed

action will require authorization by the U.S. Army Corps of Engineers

under a Clean Water Act Section 404 nationwide permit.

A number of mitigation activities would be implemented to minimize

potential impacts to the floodplain and wetlands. Operation of

construction equipment in the wetland and floodplain areas would be

minimized. Silt fences and other erosion control structures as needed

would be installed to ensure there is no deposition in the downslope

wetland areas. Minimal wetland acreage (i.e., less than 0.3 acres)

would be impacted as a result of fill associated with the

aforementioned outfall structure and placement of riprap material in

the streambed.

Additionally, an erosion control plan would be developed so that

the proposed action complies with applicable State and local floodplain

protection standards and further to ensure that no additional impacts

to wetlands will occur due to erosion and sedimentation. Best

management practices would be employed during construction and

maintenance activities associated with this proposed action.

In accordance with DOE regulations for compliance with floodplain

and wetland environmental review requirements (title 10 CFR Part 1022),

DOE will prepare a floodplain and wetlands assessment for this proposed

DOE action. The assessment will be included in the environmental

assessment (EA) being prepared for the proposed action in accordance

with the requirements of NEPA. A floodplain statement of findings will

be included in any finding of no significant impact that is issued

following the completion of the EA or may be issued separately.

Issued in Aiken, SC, on February 19, 1998.

Lowell E. Tripp,

Director, Engineering and Analysis Division, Savannah River Operations

Office.

[FR Doc. 98-5422 Filed 3-2-98; 8:45 am]

BILLING CODE 6450-15-P