[Federal Register Volume 67, Number 251 (Tuesday, December 31, 2002)]
[Notices]
[Pages 79911-79912]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 02-32996]


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

DEPARTMENT OF ENERGY

National Nuclear Security Administration, Los Alamos Site Office


Floodplain Statement of Findings for the Proposed Installation of 
a Multiple Permeable Reactive Barrier Within Mortandad Canyon at Los 
Alamos National Laboratory, Los Alamos, NM

AGENCY: National Nuclear Security Administration, Los Alamos Site 
Office, Department of Energy.

[[Page 79912]]


ACTION: Floodplain statement of findings.

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

SUMMARY: This floodplain statement of findings is for the construction 
of a multiple permeable reactive barrier (PRB) at Los Alamos National 
Laboratory (LANL). The PRB will be placed across a floodplain area 
within Mortandad Canyon, located within the central eastern portion of 
LANL. In accordance with 10 CFR part 1022, the Department of Energy 
(DOE), National Nuclear Security Administration (NNSA) Los Alamos Site 
Office has prepared a floodplain/wetland assessment and will perform 
this proposed action in a manner so as to minimize potential harm to or 
within the affected floodplain.

FOR FURTHER INFORMATION CONTACT: Elizabeth Withers, U.S. Department of 
Energy, National Nuclear Security Administration, Los Alamos Site 
Office, 528 35th Street, Los Alamos, NM 87544. Telephone (505) 667-
8690, facsimile (505) 667-9998; or electronic address: 
[email protected]. For further information on general DOE floodplain 
environmental review requirements, contact: Carol M. Borgstrom, 
Director, Office of NEPA Policy and Compliance, EH-42, Department of 
Energy, 1000 Independence Avenue, SW., Washington DC 20585-0119. 
Telephone (202) 586-4600 or (800) 472-2756, facsimile (202) 586-7031.

SUPPLEMENTARY INFORMATION: In accordance with DOE regulations for 
compliance with floodplain and wetlands environmental review 
requirements (10 CFR part 1022), NNSA prepared a floodplain/wetland 
assessment for this action. The NNSA published a notice of floodplain 
involvement (Volume 67, Number 236). This notice announced that the 
floodplain/wetland assessment document was available for a 15-day 
review period and that copies of the document could be obtained by 
contacting Ms. Withers at the above address, and that copies of the 
document were available for review at two public DOE reading rooms in 
Los Alamos and Albuquerque, New Mexico. No comments were received from 
the Federal Register notice on the proposed floodplain action.
    Project Description: In November 2002, NNSA considered a proposal 
for constructing a PRB system at a narrow constriction in Mortandad 
Canyon within LANL where contaminated groundwater is confined to a 
small cross-section of alluvial materials (see figure 1). The entire 
PRB structure would extend about 120 feet from side-wall to side-wall 
within the canyon bottom. The PRB would consist of a ``funnel and 
gate'' system to direct contaminated groundwater into a centrally-
located gate area of reactive materials. The impermeable funnel would 
be constructed of sheet piling driven to a depth of approximately 27 
feet on either side of the canyon. The permeable gate would contain 
multiple buried cells of selected media designed to react with and 
reduce the concentration of contaminants in groundwater passing through 
the gate. The PRB would be left in place for about 5 years and its 
function would be monitored through a system of shallow monitoring 
wells that would be installed at the same time the PRB was constructed. 
Construction of the PRB and associated monitoring wells will commence 
in 2003 and be completed in less than 6 months.
    Alternatives: Alternative locations for the PRB were considered but 
eliminated from future consideration. A combination of site factors was 
considered that lead to the identification of the proposed site as 
being the least disruptive to existing environmental resources in the 
area.
    Floodplain Impacts: The proposed action would have the potential 
for minimal impacts to the floodplain. Should a rain event occur during 
this activity, there may be some sediment movement down canyon because 
of the loosened condition of the soil from the clearing and 
construction activities.
    Floodplain Mitigation: Impacts to the floodplain would be minimized 
by following Best Management Practices at the construction area (such 
as the placement of silt fences, straw bales or wattles, or wooden or 
rock structures to slow down water runoff and run-on at cleared sites). 
Post-construction reseeding and re-vegetation along the sides of the 
stream channel will minimize soil disturbance and reduce or prevent the 
potential for soil erosion. No debris will be left at the work site. No 
vehicle maintenance or fueling would occur within 100 feet of the 
stream channel. Any sediment movement from the site would be short term 
and temporary.

    Issued in Los Alamos on December 20, 2002.
Ralph E. Erickson,
Manager, U.S. Department of Energy, National Nuclear Security 
Administration, Los Alamos Site Office.
[FR Doc. 02-32996 Filed 12-30-02; 8:45 am]
BILLING CODE 6450-01-P