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- Bioremediation (Natural Attenuation) – Stimulating indigenous microbial populations in the subsurface to biodegrade organic contaminates.
- Dig and Haul (Excavation and Disposal) – Bulk removals, as well as precision excavation to remove the impacted materials, followed by transportation and disposal.
- Groundwater Systems – Installation of groundwater-soil-vapor recovery systems to remove contaminated groundwater, complete treatment, and dispose of the contaminates and clean water.
- Negative Air Enclosures – Construction of temporary vapor control structures to manage the release of emissions in the work zone and to the surrounding population. Airflow is routed through a blower system and treated before being released. Work is normally performed in Level B personal protective equipment.
- NORM Excavation – Naturally occurring radioactive materials normally have relatively low concentrations of radium; however, some of the materials may contain elevated concentration and must be managed safely to limit human health exposure.
- Radioactive Soils Screening and Sorting – Radionuclides cannot be destroyed or degrade; therefore, the material must be screened and sorted before it can be treated.
- Phytoremediation – A process that uses plants to remove, transfer, stabilize or destroy contaminates in soil, sediment and groundwater.
- Tank Management – Installation and removal of aboveground and underground storage tanks used for bulk storage.
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Case Studies
SOIL REMEDIATION
THORIUM REMEDIATION PROJECT
Tulsa, Oklahoma
 Remedial Construction Services, L.P. (RECON) was awarded a contract to remediate approximately 13.5 acres of property within a commercial district in Tulsa, Oklahoma. The area of concern contained a freshwater pond, a retention pond, a former reserve pond, a flux building, and a former operations area. Characterization studies in the areas of concern indicated the presence of residual radioactive material — thorium-bearing dross, containing the isotopes thorium-232 (Th-232), thorium-230 (Th 230) and thorium-228 (Th-228).
Site PreparationOnce the client and the Nuclear Regulatory Commission approved the Work Plan, Procedures, and the Radiation Health and Safety Plan, site preparation activities were initiated. After the Health Physics Department delineated and established the controlled work zones on the property, two structures were installed to aid in the offsite transportation of the impacted materials. One structure was a 450 linear foot railroad spur and switch, and the other was a 220-foot by 125-foot asphalt-loading pad designed to prevent cross-contaminating previously remediated areas and to provide a clean working surface for loading the gondolas.
Before excavation activities could begin, a 2,000-linear foot one-pass dewatering trench with ancillary pumps and sumps was installed around the site to control groundwater infiltration. The groundwater was diverted to a newly constructed water treatment system designed to treat the water before it was released into the City´s stormwater drainage system. To protect personnel, equipment, and nearby businesses during excavation activities, 183 linear feet of sheet piling was installed to depths of approximately 22 feet.
DemolitionRECON demolished the flux building and removed the foundation slabs. The debris was scanned and sent offsite to a local disposal facility. Contaminated debris was placed into railcars for shipment to an approved disposal facility. The concrete foundations in the former operations area were excavated, sized, and scanned to determine their final disposition. The soil under both of these areas was excavated and sorted, as described below.
Excavation and RestorationOnce all the safety precautions were in place, RECON began excavating and sorting 300,000 tons of material. State-of-the art technology, consisting of a conveyor, pant leg chute with a hydraulic flop gate, stacker system, a site-specific computerized system with analyzing software and radiation detector system was used to ensure the impacted material was identified and placed in the correct stockpile for final disposition.
The excavation area was delineated into grids, approximately 200 by 100 feet in size. The area was then excavated to approximately 15 feet below ground surface, with the material being pre-sorted as it was removed. The material was transported to a feed hopper on the sorter to remove the larger rocks and debris, and then onto a feed conveyor where it was processed and sorted. The software provided an analytical report for the sorted material. Most piles were analyzed in 100-ton increments for material destined for offsite disposal and up to 300-ton batches for material proposed as backfill. RECON´s Health Physicist performed Remedial Action Support surveys on each completed grid.
| The impacted material, approximately 90,000 tons, was shipped by rail to US Ecology in Idaho. Approximately 210,000 tons of sorted material was below the action levels and returned the excavation as backfill. An imported, clean-fill cover system (10-foot thick) was installed over the material placed back into the excavation and the area was re-vegetated. |
| RECON used state-of-the art technology to identify and segregate radioactive materials. |
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CASMALIA MINERAL FEE SITES
Casmalia, California
 This project was completed by Remedial Construction Services, L.P. (RECON) under a five-year Indefinite Delivery Indefinite Quality (IDIQ) cost reimbursable (time and materials) contract with Chevron for all environmental remediation in California and the surrounding states. This location, an old oilfield, had been sold and remediation
and restoration activities were necessary before the property could be transferred.
RECON dedicated two 330 excavators and six 30-ton off-road dump trucks to this “dig and haul” project in order to remove and dispose 69,350 tons of non-hazardous petroleum contaminated soils. All the material was excavated from the two areas of concern and stockpiled before it was loaded into trucks and taken to Waste Management for disposal.
Excavation
Impacted soil was removed from two separate excavation areas. The initial excavation was located on the side of a hill and the 35,419 tons of impacted material located beneath 31,850 cubic yards of overburden. RECON removed the overburden material and set aside usable fill material for backfilling operations. The slopes of the hill had to be maintained for personnel safety and to avoid undermining adjacent power poles.
The second area to be excavated was located at the bottom of the hill. Groundwater was encountered at 4 feet and the excavation needed to extend an additional 3 feet. In order to avoid dewatering the excavation, the area was divided into grids or “slots”. The first slot was excavated, followed by the third slot. After confirmation samples were verified, the first and third slots were backfilled and the second slot was excavated. This continued until all 33,931 tons of impacted
material was removed. RECON was able to use the groundwater that accumulated in the excavation to assist with the compaction efforts.
Backfill and Restoration
T he excavations were backfilled using 99,713 cubic yards of fill from the initial excavation’s overburden material
and from an onsite borrow pit. The borrow pit was depleted and the area reclaimed.
The 30-acre site was hydro-seeded. Silt fences and hay bales were strategically placed to assist with erosion control efforts.
Work also included the demolition and restoration of a 150-foot by 350-foot former rodeo arena
that was located on top of the second excavation. |
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| "RECON constructed a 19.7-acre cap over a combination of hazardous and non-hazardous waste." |
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