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PROJECTS:  ENVIRONMENTAL REMEDIATION

MGP Site Remediation

Forgen has extensive experience with the remediation of complex Manufactured Gas Plant (MGP) sites including polyaromatic hydrocarbons (PAHs), semi-volatile organic compounds (SVOCs), heavy metals, and asbestos. Our management team understands the logistics and project controls related to odor and water management required to successfully complete these projects while performing work in urban environments involving numerous stakeholders. Our company owned specialty equipment and personnel resources allow us to self-perform all phases of MGP remediation from site preparation through project execution and site restoration. Forgen’s unique skill set includes barrier wall construction, In Situ auger mixing, contaminated source removal, and groundwater/soil remediation systems construction. These capabilities enable us to implement In Situ, Ex Situ, or hybrid combinations of these methodologies while working with MGP sites.

SHORELINE MGP SITE REMEDIATION
San Francisco, California

  • MGP site remediation on the shore of San Francisco Bay
  • High visibility urban setting with difficult logistics and intense oversight
  • Installation of turbidity curtain and oil containment booms to protect the Pacific Ocean
  • Demolition of remaining structures and excavation of MGP waste and contaminated sediment
  • Construction of revetment including placement of a Reactive Core Mat (RCM), 800 tons of filter rock, and 1,500 tons of armor rock
  • Site restoration including asphalt paving and fencing

Forgen completed the interim Shoreline Maintenance Project at a former MGP site on the Potrero Power Plant property in San Francisco, California during the winter of 2010, fulfilling the primary construction role on a CPUC Diversified Contractor-led team. The project involved demolition of remaining structures, selective excavation of impacted inter tidal sediments, and construction of a contaminant system consisting of a reactive core mat (RCM) and protective rock armor revetment. The work scope included installation of a silt turbidity curtain and containment boom along the shoreline of San Francisco Bay, demolition of an existing pipeline and concrete structures, excavation of approximately 500 cy of Manufactured Gas Plant (MGP) waste and contaminated sediment along the shoreline, off-site disposal of excavated waste, installation of a reactive core mat (RCM), and placement of 2,500 tons of rock armor revetment.

The project took place in a highly visible urban setting along the waterfront in downtown San Francisco. The site’s location and restricted work footprint presented additional logistical challenges for conducting the work and facilitating off-site waste transportation. Forgen began the project by demolishing abandoned above ground pipelines and concrete structures. Work included removing pipeline, pipe stands, concrete pads, and off-site disposal of a variety of asbestos containing materials (ACM) including piping, tiles, treated wood, and other debris scattered along the shoreline.

Prior to excavating in the tidal zone, approximately 400 lf of Type III turbidity curtain and oil containment boom were installed. A toe trench was excavated and surface sediments were removed to allow placement of the armor rock for the revetment. MGP waste and contaminated sediments were selectively excavated in a sequence of rectangular grids approximately 30 feet wide and parallel to the shoreline. Excavated sediment was staged near the point of excavation within the impacted zone and allowed to free drain prior to being relocated to the lined waste management area for load out and shipment to the Class I disposal facility.

After excavation in an area was completed, RCM was installed followed by initial filter and armor rock placement to secure it. The final revetment consisted of approximately one foot of filter rock and three feet of armor rock. All excavation and rock placement was performed using conventional hydraulic excavators working from the shoreline.

The project was performed during the winter and presented many challenges including heavy rain and pounding surf. Forgen was commended by the Owner for completing this project without a single environmental Notice of Violation (NOV) and for a ZERO INCIDENT safety performance.

FORMER MGP SITE REMEDIATION
Albion, Michigan

  • Dredging of 8,900 cy of MGP tar-impacted sediment
  • Dewatering and off-site transportation
  • Water treatment filtration system and testing
  • 100% compliant to NPDES permits
  • Multiple stakeholder project involving the Michigan Department of Environmental Quality, Michigan Department of Natural Resources, and the City of Albion

Forgen performed remediation services at this former manufactured gas plant (MGP) in Kalamazoo, providing removal and disposal of the impacted sediments. Forgen’s assessment of the requirements identified some risks that were mitigated in the work approach, including potential for over-dredging which would increase dewatering, water treatment, and landfill costs. This was mitigated through a combination of vacuum and mechanical dredging systems which incorporated state-of-the-art on-board dredging controls and post-dredge monitoring equipment.

The North Eaton Street Bridge presented unique challenges to this project with limited available head room beneath the bridge creating access restrictions. Forgen’s patented Sed-Vac system proved to be an effective dredging method to deal with the height restrictions of the bridge, and allowed for safe removal of material from utilities.

A diver was used when dredging near utility lines providing real-time observation and direction of the removal activities. Forgen also used a diver during back filling operations around the utilities. Forgen’s extensive experience providing remediation of the Kalamazoo River and other similar rivers led us to propose a change in the turbidity curtain layouts provided by the Client which provided a more effective design. Major elements of the work scope included:

 

  • Dredging, stabilization, dewatering, waste transportation and waste disposal services for the targeted sediment
  • Site restoration
  • Installation of fish barriers and relocation of amphibious wildlife
  • Suspended sediment controls, absorbent booms, and dust control
  • Implementation of MOTs for public vehicle traffic and detours for pedestrians and cyclists
  • Precision removal guided through use of tilt sensors and RTK/GPS