- Company: Dte – Environmental Division
- Category: Soil Remediation Within a Wetland Area
- Location: Six Lakes, Michigan
- Date: June – July 2009
- Cost: $183,000
- Focus: Mercury-Impacted Soil Remediation Within, a Wetland Area Located Contiguous to a Lake
Michigan ● Taggart Compressor Station ● Six Lakes ● Active Gas Compressor Station
Wetland soil impacted by improper disposal practices involving heavy metal (mercury).
Objective – remove mercury-impacted soil within a regulated wetland, contiguous to a lake.
Clearing and grubbing of trees, stumps, roots and other vegetation to the anticipated depth of the remedial activities
Trees downed in designated wetland areas were stockpiled and redistributed across the wetland at completion of the work
Per the wetland permit, stumps from trees removed only for access purposes (and not in the remedial area) remained in the ground to promote reforestation.
Excavation, stabilization, transport, disposal of 1700 CY of mercury-affected, shallow wet soil from an approximate 0.8 acre area, of which 0.75 acres was defined as wetland.
- ERG surveyed the layout of the planned excavation work limits for 0.5 - 2.5 foot excavation depths
- Survey stakes were set to delineate each post-excavation soil verification sampling location
- Pre-excavation elevations were set in the work area on a 25 foot grid
- 1,250 feet of silt fence was installed in accordance with Montcalm County’s Soil Erosion Permit.
- The Wetland Restoration Plan was completed, which included installing eight (8) rip-rap check dams
- Installing 200 linear feet of silt fence at each check dam
- Constructing seven (7) check dams with logs salvaged from clearing activities
- Placing excess downed trees within the restoration area
- Placing 1,055 feet of re-vegetation mat along the edge of the excavation area in accordance with the Soil Erosion and Sedimentation Control Permit
- Re-seeding and planting wetland trees
- Grading site to match pre-excavation 25-foot grid elevations.
- ERG documented reconstruction of the wetland with a final as-built survey, which included coordinates along the perimeter of the graded wetland restoration area, excavation boundaries, excavation bottom elevations, center of each check rock dam and each log check dam, and soil verification sampling locations.