Significant Project Features
- Sevenson self-performed excavation of 6,844 CY of soil and 8,030 CY of sediment, from multiple areas spanning a 14.5-acre site, impacted by a range of COCs, specifically heavy metals, PFAS, PNAS, VOCs, and SVOCs
- Managed the transportation and disposal of excavated soil and sediment to an off-site landfill
- Site restoration activities included placing and compacting backfill and topsoil material
- Field crews logged a total of 17,576 safe workhours without a lost-time incident
History & Location Details
Historically, this site was used in the 1800s as an icehouse, lumber yard, and coal storage unit. A shoe factory was then constructed in 1903, and the tannery was later constructed in 1908. The tannery was operated until 2009 and demolished in 2011. The foundations of the demolished tannery buildings were left in-place, covered with fill and topsoil, and seeded. In certain locations, up to 8 ft. of fill material was placed over the remnants of the foundations. A retail outlet store and paved parking areas remain on the site.
The site encompasses a Tanner property sites between Main Street and the Rouge River, where the site is divided by Rum Creek, which flows from east to west through the central portion of the site and discharges into the Rogue River. Primary COCs included VOCs, SVOCs, PNAs, heavy metals (including chromium and lead) general chemistry analytes, and PFAS compounds. Hides and leather scraps were also encountered.
Site Preparation and Mobilization
Sevenson began work on pre-mobilization submittals, such as all required work plans, and obtained a sidewalk closure permit. Crews removed portions of the existing chain link fence; erected temporary fencing; performed clearing and grubbing operations; installed the necessary soil erosion and sediment controls; constructed the temporary staging pad(s) and access roads; and established temporary offices. Sevenson’s temporary facilities consisted of an office and break trailers, temporary access roads, a temporary rerouting of White Pine Trail, as well as parking lots for site personnel. Sevenson contacted the local “Call 811” service to locate existing utilities within the work zone, such as overhead electric lines, subsurface gas piping, and storm sewers. Utility infrastructure was marked out. Several overhead electric lines exist north of Rum Creek within the excavation area. These lines were supported and protected in order to perform excavation and backfilling operations. Sevenson contacted the local utility company and the utility company secured the pole while the field-crews performed work activities.
Upland Soil Excavation
Sevenson excavated 6,844 CY of contaminated soil from various areas of this site. The northern excavation area consisted of three areas (N1, N2A and N2B) that required different depths of excavation, ranging from 3 ft. to 5 ft. In order to complete excavation operations along the shoreline, Sevenson installed a temporary cofferdam consisting of a combination of sheetpile and water-filled bladderdam. The cofferdam ends were installed north and south of the excavation areas and connected to the shoreline to provide an adequate seal and allow for a dry excavation along the shoreline for excavation areas N1 and N2.
To facilitate excavation zone dewatering, Sevenson pumped the water from within the excavation area into the Rogue River. The water was first conveyed through a bag filter housing to capture any suspended solids. The regenerative water was handled in the same manner as the initial drawdown water. Sevenson utilized a PC300 excavator to remove soil and live load tandem dump trucks. As the soil was removed, the excavation operations proceeded south. The area remained dewatered to allow for the collection of soil and sediment samples where applicable.
After all contaminated soil was removed in Area N1, Sevenson continued excavation operations in Areas N2A and N2B. Since the cofferdam had already been installed and the area had been dewatered, the excavation operation was seamless. Excavation Area N2 consisted of areas with three different excavation depths. The western shoreline area consisted of a 3 ft. excavation; the eastern adjacent upland soil required a 1 ft. excavation depth; and a small portion in the northeastern corner required a 5 ft. excavation (N2B). After field personnel completed the soil removal in Area N2, field crews proceeded to the Southern Excavation Areas, south of Rum Creek. The southern excavation areas consisted of four isolated upland excavation areas. Areas S2, S3, and S4 required the removal of 3 ft. of soil and Area S1 required the removal of 10 ft. of soil.
Once the temporary cofferdams were installed, Sevenson dewatered the area inside the cofferdams by pumping the water through bag filters into the Rogue River. Due to the excavation depth of 10 ft. for Excavation Area S1, Sevenson was required to slope a portion of the excavation to prevent slope failure during removal.
Using a PC 300 excavator, field crews also removed 8,030 CY of sediment from six different areas. These areas were located along the shoreline in the northern and southern areas of the site. Sediment Areas N1 and N2 were located to the north of Rum Creek adjacent to the shoreline of the upland excavation areas. Sediment areas S2, S6 and S7 were located south of Rum Creek at the northern portion of the southern excavation area and Sediment Areas S4 and S5 were located at the southern portion of the southern excavation area. To remove the sediment from these areas, Sevenson installed temporary sheetpile and water bladderdam cofferdams in the same manner as the excavation areas that were located in the northern area. Sevenson mobilized equipment and materials in quick fashion to install the temporary sheetpile cofferdam. Sevenson’s fleet of available equipment (sheetpile and pile installation equipment) allowed for quick installation and limited economic impact to the project.
Sediment was removed to 2 ft. to 3 ft. BGS. The sediment was loaded into off-road dump trucks and was transported to a sediment staging pad that Sevenson constructed on the upland portion of the site. After the sediment was decanted and amended with portland cement, as needed to pass the paint filter test, it was loaded into dump trucks for transportation to an offsite landfill for disposal. After Sevenson removed the required sediment, GZA (the Client’s engineer) obtained the post-excavation sediment samples for chemical analysis.
Backfill and Rip Rap Placement
Once Sevenson completed the removal of soil and sediment and received confirmation sampling approval, field crews initiated the placement of geotextile and backfill materials. An anchor trench was installed in the Rogue River parallel to the shoreline to secure the geotextile. This trench was excavated during the sediment removal operation. The rip rap was placed on the geotextile in the anchor trench first and it extended up the slope to the required elevation. Field crews installed 1,280 tons of rip rap. Each roll of geotextile was deployed with a minimum of 12 in. overlap at each seam. As backfill was placed it was graded in 12-in. loose lifts with a bulldozer and compacted with a roller. Sevenson procured the services of a local geotechnical lab to perform third-party compaction testing on placed fill. Crews then performed a minimum of 1 test per lift for every 1,000 sf.
Construction Water Management
Based on test pits conducted adjacent to S1, and its proximity to Rum Creek, the estimated ground water that would be generated during soil removal was approximately 45,000 gallons. Therefore, a frac tank was utilized during soil removal of excavation area S1 to containerize groundwater. Sevenson was required to excavate upland soils beyond groundwater elevation due to confirmation sampling and the presence of leather scraps. A minimal amount was containerized at the end of the project when equipment was decontaminated prior to removal from the site. All water was transported and disposed by GZA (the Client’s engineer).
Transportation and Disposal
The project required disposing of multiple waste streams. Upland soil and sediment were shipped to Envirosafe located in Otter Creek, Ohio. In addition to the soil and sediment, contact water from excavation area S1 and decon water was containerized, transported and disposed offsite by the Client’s Engineer.
Restoration activities required the removal of a permanent chain link fence; the restoration of asphalt on White Pine Trail; placement of backfill and topsoil; placement of an erosion control blanket; and establishment of wetland turf planting zones. Crews also constructed new concrete sidewalks and restored concrete aprons.
Equipment Decontamination and Demobilization
Upon removal of the permanent chain link fence and placement of the final cover, Sevenson decontaminated of all equipment by pressure washing. Following decontamination, all equipment was demobilized from the site.