Summary

On April 21, 2023, EPA received a request from the Environmental Division of the Directorate for Public Works at Joint Base Lewis-McChord for a Clean Water Act Section 401 Water Quality Certification for the Repair Diversion Structure at Lake Sequalitchew Project [Seattle District Corps of Engineer’s permit project number NWS-2022-900, applied for under Nationwide Permit 43 for stormwater management facilities].

Section 401(a)(1) of the Clean Water Act requires applicants for federal permits and licenses that may result in discharges into waters of the United States to obtain certification that the discharge will comply with applicable provisions of the Clean Water Act. Where no state agency or tribe has authority to give such certification, EPA is the certifying authority.

In this case, the project occurs on Joint Base Lewis-McChord which is a land of exclusive federal jurisdiction. Therefore, EPA is making the certification decision for discharges that may result from the proposed project.

EPA is requesting comments on its Clean Water Act Section 401 water quality certification for the proposed project.

As a certifying authority, EPA must decide whether to:

1. Grant certification as proposed.
2. Grant certification with 401 conditions.
3. Deny certification.
4. Waive certification.

Project Description

The proposed Repair Diversion Structure at Lake Sequalitchew Project is located on Joint Base Lewis-McChord (JBLM) near the town of Dupont, Washington (latitude 47.112, longitude -112.617).

The project purpose is to repair the existing outlet diversion weir and canal-creek cross-over culverts downstream of the Lake Sequalitchew outlet to restore the normal storm flows to Sequalitchew Creek while diverting higher storm flows to the north JBLM stormwater canal.

Currently, the canal-creek cross over culverts are not functioning as intended and direct most of the groundwater and stormwater in-flow from Lake Sequalitchew and Hammer Marsh into the JBLM stormwater canal. The project will restore the original intent of the outlet diversion weir to handle only overflow from the lake and marsh, with normal base and seasonal flows directed to Sequalitchew Creek.

The proposed action is to implement a new outlet diversion weir system at the tailwater of the triple reinforced concrete box bridge structure to restore stream flow to Sequalitchew Creek, regulate the lake level, and to prevent backwater flow from entering the Sequalitchew springs water distribution system. The canal-creek cross-culvert pipe is to be removed, and hydraulic connectivity re-established from the canal-marsh system to the creek with a new connecting channel.

Repairs will include removal of:

• Four 42-inch corrugated metal pipe culverts.
• Two 18 inch corrugated metal pipe culverts.
• An existing concrete fish exclusion structure at the Lake Sequalitchew outlet.
• Existing buttress structure within uplands adjacent to Sequalitchew Creek.
• An existing beaver dam.

Repairs will also include construction of:

• An open channel profile where the canal-creek crossing occurs.
• Three reinforced concrete weirs – one within Sequalitchew Creek and two within the JBLM stormwater canals (30 cubic yards of fill).
• Concrete block mats along the banks of the creek and canal at each concrete weir location for scour protection (20 cubic yards of fill).
• A gravel access paths within the uplands above the ordinary high water mark of Sequalitchew Creek and JBLM stormwater canal.

These activities will impact 0.14 acres/400 linear feet of Waters of the U.S.

Project impacts will be minimized by:

• Performing construction activities during the approved in-water work window.
• Implementing temporary erosion and sediment control best management practices.
• Utilizing temporary stream diversion materials.
• Other in-water work isolation measures as determined by the contractor.