CAMU Construction, Phase 1 The initial phase of this refinery closure and redevelopment required the construction of a 13-acre lined CAMU cell, a lined water retention basin, and access roads in preparation for placement of remediation wastes from a former refinery located approximately 4 miles away. The cell was constructed with a design capacity of 320,000 cubic yards of waste and was the first of four cells permitted for construction at the site.

The work required clearing, grubbing, and stripping of 40 acres of native vegetative cover materials. The topsoil strippings were stockpiled for use on the outside embankment slopes of the CAMU cell and for construction of the cover and cap. The work area was then enclosed by 7,000 linear feet of 6-foot high chain link fence. Inside the perimeter, Envirocon installed 5,000 linear feet of silt fencing for stormwater run-on/run-off control and 1,500 linear feet of erosion control structure consisting of gravel lined collection trenches and straw bales.

Once construction control was established, layout and construction began for the retention basin, lay down and staging areas, temporary facilities, and access roads using 60,000 cubic yards of native materials as construction fill. In order to meet the project goal of substantial completion by June 22, 2001, construction of CAMU Cell #1 began in early March during winter weather conditions. Construction of Cell #1 required excavation, blending, placement, and compaction of approximately 250,000 cubic yards of native sand and clay materials. Earthwork for Cell #1 and the retention basin was completed and ready for liner installation in 60 working days.

Envirocon subcontracted the liner systems installation to a specialty subcontractor. The liner subcontractor installed a 40-mil LLDPE liner in the retention basin and a three-layer system in Cell #1. The Cell #1 lining system consisted of GCL contacting the embankment and cell bottom, a textured 60-mil HDPE as the second layer, and geo-composite netting as the final layer. Envirocon then placed 24 inches of native soil as a cover/protective layer for the liner system and constructed access/egress ramps using more native soil materials.

Envirocon utilized internal resources for all construction control, survey, layout, construction staking, and as-built surveys as well as all field density testing, soils classification, and quality control. Additionally, Envirocon provided value-engineering suggestions that increased the volume available for waste in Cell #1. Envirocon's ideas resulted in an overall cost reduction of $2.00/cubic yard of cell air space compared with original engineering estimates. Envirocon design input also resulted in the construction of an additional 60,000 cubic yards of disposal capacity at no additional cost. The project was finished 3 weeks ahead of schedule and substantially under budget.

Refinery Property Pipe and Impacted Soil
Removal After completion of the CAMU, Envirocon was awarded a second major project at this site through a competitive bidding process. The original work scope of this pipe and soil removal project included excavation, decontamination, sizing, and recycling of 500,000 linear feet of refinery process piping. In addition Envirocon was responsible for the excavation, stockpiling, and crushing of 55,000 tons of concrete, and demolition of seven crude oil storage tanks, several buildings, and the electrical power system.

Excavation and removal activities uncovered additional buried concrete foundations and pipe corridors. Envirocon ultimately removed more than 1,000,000 linear feet of underground process pipe and 350,000 tons of highly reinforced concrete. All refinery process piping was cleaned, sized to 20-foot lengths, and shipped to a recycling facility as scrap. Steel tanks, buildings, and other miscellaneous steel structures were sold for re-use or sized and sold as scrap. All concrete foundations, slabs, and structures were removed and stockpiled for processing into aggregate products that were re-used on roads, parking lots, or foundation pads. Concrete processing required removal of rebar, a two-phased crushing operation, magnetic removal of any remaining steel, washing, and staging in a stockpile with a stacking conveyor.

The project also recovered more than 91,000 gallons of recyclable liquid hydrocarbons and 20,000 tons of recyclable scrap steel. Substantial quantities of impacted soil, asbestos containing material (ACM), and non-recyclable debris were removed from the pipe corridors and transported to the CAMU for disposal. In conjunction with on-site pipe and foundation removal, Envirocon also removed pipe and concrete debris from a 1.5-mile stretch of the North Platte River, along the northern boundary of the former refinery site. Refinery Site Redevelopment Activities During 2003, Envirocon continued Pipe and Foundation removal on the former refinery.

In conjunction with these remediation activities, Envirocon also conducted a number of site redevelopment projects including:

• Rough grading an 18-hole Robert Trent Jones Championship golf course;
• Installing ponds, piping, and mechanical components for a wetlands treatment system;
• Replacing API Separator and perimeter groundwater recovery wells;
• Installing office park roadways and utility corridors; and
• Constructing a recreation kayak course in the North Platte River.

In conjunction with establishing the rough graded surface features of the golf course, Envirocon also constructed lined ponds and installed the piping and mechanical components of a wetlands treatment system. The system was designed to treat hydrocarbon-impacted groundwater and surface water using a series of aeration ponds that maintained the appearance of standard golf course water hazards surrounded by native vegetation. Most of the earthwork required for the construction of this system occurred in soils impacted by heavy metals and hydrocarbons associated with former refinery operations. This work was scheduled and sequenced in coordination with site-wide removal of underground piping and foundations, capitalizing on the fact that OSHA 40-hour trained crews were already working in the impacted subgrade where these features had to be installed.

Construction of the parkway road and utility corridors also occurred in subgrade impacted by a variety of contaminants and was done in coordination with site wide underground pipe and foundation removal. Utility installation included water mains, sewers, electrical, and communications corridors. Utilizing Envirocon's OSHA 40-hour trained crews to conduct this work while already in these areas rendered operational efficiencies and eliminated potential coordination problems with other contractors. Hazardous wastes, asbestos, or other impacted media encountered during excavation were readily removed and managed without interrupting the construction of the roads or installation of the utilities.

The kayak course required strategic placement of large imported boulders in conjunction with the construction of four river-wide wide low-head structures designed to channel flow into whitewater features suitable for recreational river sports. To protect the fishery and to take advantage of the lowest river flows, the course was constructed during the winter months. Flows averaged between 400 to 450 cfs for the duration of the project with most of the work taking place directly in the river. Inflatable water bladders were used as temporary diversion dams to direct flow around areas where the structures were being built, typically blocking half the river at any given time. Construction began with the uppermost feature and proceeded downstream. Clean, recycled concrete from the refinery foundation removal project was used as base material for each of the structures. Once established, each feature was completed with imported river rock and grouted in place.

Waste Unit Removal
The work scope for the North Area Properties Waste Unit Removal included excavation, stabilization, transportation, and CAMU cell disposal of relic refinery wastes from 13 former disposal areas located off site from the main refinery property. Several of these waste units, including a former land farm, were located in the tank farm areas across the North Platte River from the refinery. Others were located directly adjacent to the river, along major roadways bordering the refinery, and amidst a variety of nearby businesses and industrial properties. Many of these sites were in high visibility areas requiring strict adherence to protocols governing traffic control, odor control, location and protection of utilities, spill prevention, and protection of the public at large. More than 500,000 cubic yards of refinery waste and contaminated soil were excavated from these sites and placed in the CAMU cell constructed and operated by Envirocon.

Prior to excavation at each waste unit, Envirocon established survey control and installed erosion protection measures. The waste was then excavated, pre-stabilized (to eliminate free liquids and adjust pH if necessary), assigned a unique tracking number, loaded into haul trucks, and transported to the CAMU. Once at the CAMU, waste materials were received, placed, and mapped (using a grid system), further stabilized (if necessary), and compacted using a CAT 815 padfoot compactor. Daily field production and corresponding waste receipts at the CAMU ranged from 1,500 to 2,000 cubic yards per day depending on the characteristics and condition of the various materials encountered in the field and the degree of amendment or treatment they required. Waste materials encountered during the North Area Properties Waste Unit Removal included asbestos contaminated soils, metals contaminated soils, tank bottoms, and other refinery waste impacted media. Envirocon excavated contaminated media from a variety of challenging settings including from around buildings at depths of up to 15 feet and while working around overhead power lines, underground utilities, and traffic. Upon completion of excavation activities, each property was backfilled, regraded, and restored. One particularly challenging waste stream was the acid clay filtration sludge located in "Area D" of the former North Tank Farm.

Acid Clay Filtration Sludges
The Acid Clay Filtration sludges were very low pH, hydrocarbon sludges that had a pH of 0.25. More than 50,000 cubic yards of these sludges had been previously stored or disposed of in a concrete vault in the North Tank Farm. Envirocon utilized locally available pozzolanic reagents and other suitable refinery waste to adjust the pH and physical condition of these sludges to make them suitable for disposal in the CAMU. Reagent was delivered in bulk to a covered containment area near Area D via live floor transports and a loader was used to deliver reagent and blending soils to the sludges which were then mixed with an excavator bucket. Criteria for shipment to the CAMU were a pH above 4.0 and a physical condition suitably free of liquids to pass the paint filter test. Once at the CAMU, these wastes were received, placed, and compacted by Envirocon CAMU Operations personnel, usually without further treatment. The nature of this waste (and many of the others encountered on the North Properties) necessitated thorough decontamination of the haul trucks at both the point of origin and prior to leaving the CAMU.

CAMU Cell #2
During 2002, a second CAMU cell with a design capacity of 500,000 cubic yards was constructed to accommodate additional waste unit material from the North Area Properties as well as contaminated sediments from the Soda Lake Inlet Basin Remediation. CAMU Cell #2 was constructed directly adjacent to, and shared a common berm with, Cell #1. In anticipation of the need for the second cell, much of the clay and borrow material required for the construction of Cell #1 was mined from the footprint of Cell #2 and stockpiled for later use in the construction of the second cell. This approach resulted in substantial cost savings as well as savings of time and effort in the field. At project completion, the combined volume of wastes managed in the CAMU cells was nearly 1 million cubic yards.

Inlet Basin
Having successfully implemented a variety of cost saving ideas on active projects at the Casper site, Envirocon was asked to submit a proposed methodology and budgetary estimate for the remediation of a large inlet basin that had received refinery effluent discharge since 1958. The inlet basin contained an estimated 350,000 cubic yards of refinery sludges and impacted sediments. The primary remediation methods under consideration to that point had been capping or removal options requiring hydraulic dredging that each had price tags in excess of $20M. Envirocon proposed passive dewatering and drying of the Inlet Basin followed by excavation and placement of the impacted sediments in a second CAMU at a total estimated cost that was less than half the cost of the other options. The conceptual approach and budgetary estimate were submitted within 2 weeks of the request and were quickly followed by sampling and bench scale treatability studies to confirm the viability of the approach. Independent treatability studies conducted by the consulting engineer further validated the methodology. Envirocon's approach was subsequently incorporated into the approved Remedy Decision for the Inlet Basin signed in January 2002.

Once approval was obtained for the approach, Envirocon collaborated with the client and consulting engineer to develop an approved work plan for remediation of the Inlet Basin. Passive and active dewatering activities began during the summer of 2002 and continued on an intermittent and seasonal basis, successfully completing in 2006.

• Excavating and stabilizing refinery wastes from 20 former disposal areas
• Performing value engineering which saved the client $15 million
• Constructing two CAMU cells
• Transporting and placing waste in CAMU