Former Zephyr Oil Refinery Site – Fire Suppression Ditch Area Remediation
Significant Project Features
- USEPA Great Lakes National Program Office (GLNPO) project to remove approximately 48,870 cubic yards of contaminated sediment from 15 acres of wetlands along the Muskegon River.
- Excavation of a former fire suppression ditch present in the wetland.
- Sediments contained elevated lead and total petroleum hydrocarbons with strong refinery waste odors.
- Sediment removal required excavating to meet design elevations 2-ft to 3-ft cut across the wetland areas.
- Excavated sediment transferred to a designated upland staging area on the property for stabilization prior to off-site landfill disposal.
- Restoration of wetland areas according to permit requirements and specifications.
History & Location Details
The former Zephyr Oil Refinery site is located within the Muskegon Lake Area of Concern under the 1987 Great Lakes Water Quality Agreement. The agreement is a commitment between the U.S. and Canada to restore and protect the water of the Great Lakes. The USEPA’s Great Lakes National Program Office (GLNPO) is managing the project. The Zephyr Oil Refinery operated for more than 40 years, and historical releases of petroleum to the Muskegon Lake watershed have contributed to contamination of the sediment, groundwater, and wetlands surrounding the former refinery. This project required the remediation of the fire suppression ditch and adjacent wetlands.
Sevenson was awarded this contract on a competitive bid basis. Scope of work included:
Water Control Structure Installation
A three-component cofferdam was installed to prevent water from the Muskegon River from entering the excavation areas. Component one consisted of construction of an 880-ft earthen berm; component two required installation 176-ft of steel sheet pile; and component three required placement of 50-ft of sand filled super sacks. Sheet pile was also installed as shoring along both sides of the suppression ditch for excavation support. Shoring was installed adjacent to the suppression ditch in three phases proceeding south to north. Each phase required approximately 350-ft of sheeting.
Sediment was excavated from the ditch, surveyed, sampled and back filled with clean sand prior to removing sheet pile.
Access Road Development
Sevenson improved the existing access roads and constructed two new access roads to gain access to/from the excavation areas and sediment dewatering pad. All access roads were constructed to establish elevations. Access roads were improved by placing 6-in. of crushed stone on top of an 8-oz. nonwoven geotextile material. The stone was dumped then spread with a D61PX dozer. A smooth drum roller then compacted the stone. Sevenson constructed pipe crossings over an existing pipeline. The crossing consisted of 24-in. of Coarse Aggregate No. 2 on top of a high strength woven geotextile layer. Timber mats were placed on top of the crushed stone for a span of 30-ft. on each side of the pipeline.
Wetland and Ditch Dewatering and Excavation
48,870 CY of contaminated sediment were excavated from the wetland area and the Fire Suppression Ditch area.
In order to remediate the ditch, the MDEQ discharge pipe was extended 1,700 ft. to the Muskegon River. A temporary 4-in. diameter HDPE pipe extension was installed above ground along Improved Access Road 2 on the east side of the wetland area to a new discharge point location at the river. The pipe was fusion welded and secured with sand bags. The piping was watertight and capable of being pressure tested. The temporary pipe was removed and the discharge point returned to its original position when work was completed.
Prior to Phase 2 excavation in the Fire Suppression Ditch, the adjacent operating fertilizer plant water supply pipeline had to be cut and removed. A temporary pipeline was installed to provide the necessary water supply to keep it operational. The temporary line was an 8-in diameter HDPE pipe installed above ground along Improved Access Road 2 on the east side of the wetland area. The pipe was fusion welded and secured with sand bags. A 6-in. pump was installed to pump water, as needed, during the remediation from the Muskegon River to the fertilizer plant. The water was pumped through bag filters to maintain a low turbidity water supply.
Fire Suppression Ditch Excavation
13,224 CY of contaminated sediments were excavated from the Fire Suppression ditch. The ditch was excavated in three phases in 340-ft. sections. Silt curtains were placed across the ditch, in coordination with the three phases, to prevent recontamination of the completed portions of the ditch. To safely excavate the sediments, temporary shoring (sheet pile) was installed on both sides of the ditch. 30-ft. long sheet piles were driven to a depth of 18-ft. BGS. A RoboVibe vibratory hammer attached to a PC300 excavator installed and removed the sheets for each phase of the ditch excavation. A PC400 excavator with a long stick, fitted with an environmental bucket, accessed the ditch from Access Roads 1 and 2. The ditch excavation advanced from the south end of the ditch to the north end, removing sediments. Excavation depths ranged from 3–10-ft.
Wetland Area Dewatering
Sevenson pumped wetland area surface water at a rate of approximately 700 gpm for four days to gain access. The water was treated in a temporary onsite wastewater treatment system (WWTS). To excavate wetlands in dry conditions, accumulated water in the wetland excavation areas was channeled via berms and swales to a sump, where it was collected and stored in temporary holding tanks then pumped through an 8-in diameter HDPE above ground pipe to the WWTS for treatment and discharge. The HDPE pipe was anchored with sand bags and corrugated metal pipe culverts were installed where the HDPE pipe crossed haul routes. Holding tanks were placed on a lined pad consisting of a 6-in thick sand base layer, a 40-mil HDPE liner, an 8-oz. nonwoven geotextile layer, and 8-in of Coarse Aggregate No. 1.
Wetland Area Excavation
Sevenson excavated a total of 35,646 CY of contaminated sediments from the wetland area. 1,370 CY was identified as hazardous waste. Temporary ramps comprised of timber mats were constructed to provide access to the wetland excavation areas. The wetland excavations advanced from the south end of the site to towards the north end and were performed concurrently with the Fire Suppression Ditch phased-excavation. Sevenson established 50-ft x 50-ft grids to maintain quality control. Excavation depths averaged 3-ft Sevenson utilized one CAT 349E long front excavator and two PC300 excavators to excavate the wetland area. As sediments were excavated, they were loaded into off-road dump trucks and hauled to the dewatering pad for staging and dewatering.
Sevenson performed excavation confirmation consisting of post-removal surveying and confirmation sampling and analysis to ensure that contaminated sediment removal was complete.
Sand Backfill – Fire Suppression Ditch
Upon approval of confirmation sample results, Sevenson placed sand backfill consisting of ASTM C33 Concrete Sand in the Fire Suppression ditch. The sand was imported and stockpiled in the material staging area prior to placement. The sand backfill was placed in approximate 18-inch-thick lifts using a PC400 excavator. It was placed to reform the ditch with a new invert depth of approximately 2-ft. below the existing invert.
Sediment dewatering consisted of a combination of gravity dewatering and solidification. The sediments required approximately five days of gravity drainage in order to pass the Paint Filter Test required for disposal. To accomplish this, Sevenson spread the sediments on the dewatering pad, subjecting it to the sun and wind. Sediments that did not pass the Paint Filter Test after the five days were mixed with Portland cement utilizing a PC300.
Transportation and Disposal
Once processed, Sevenson utilized PC300s to load the sediments into dump trucks for transportation and disposal at an off-site landfill. The trucks were decontaminated before leaving the site. The bed of each truck transporting sediments from the hazardous waste area was lined before loading, and covered after loading, prior to leaving the site.
Restoration included backfilling emergent marsh areas, the removal of the temporary access roads and ramps, material staging areas, dewatering and wastewater treatment system pads, and the decontamination pads. Wetland designated for emergent marsh construction were backfilled. Prior to importing clean backfill to the site, backfill material was subjected to physical and chemical analyses. Access roads and decontamination pad materials were stripped. Once materials were removed Sevenson sampled soils from the areas for analytical testing to ensure that disturbed areas were restored to their original state. When confirmation was received the disturbed areas were regraded placing a 2-inch topsoil layer, seeds, and mulch.