In 2009, under the Kansas Department of Health and Environment (KDHE) Dry Cleaning Trust Fund Program, Burns & McDonnell and Remediation Services Inc. (RSI) completed a multifaceted corrective action at the former Bentley's Garment Care facility in Neodesha, Kan. The corrective action was designed to reduce risk to human health and the environment by removing soil contaminated with tetrachloroethylene (PCE) from beneath a building structure - while also allowing current building tenants to conduct normal daily business activities.
Careful planning and staging of pre-remediation activities by Burns & McDonnell, along with implementation of measures designed to protect building occupants during the corrective action, allowed removal of contaminates with minimal disruption and without compromising safety.
Site Location
Neodesha is in southeastern Kansas between Kansas City, Mo., and Tulsa, Okla. (See Figure 1.) A dry cleaner that began operating in 1981 was located at a facility currently housing a hair salon and a coin-operated laundry with a dry cleaning drop-off location. The facility is at the intersection of eighth and Tank Avenue, immediately north of Neodesha High School. Land use in the vicinity of the facility is primarily residential, with baseball fields and the Neodesha High School to the south and southwest of the facility, respectively. Residential properties are north, east, and west of the site.
Site Geology and Hydrogeology
The regional geology of the Neodesha area consists of unconsolidated Pleistocene sediments comprised of alluvial silt deposits, sand and gravel within the river valleys, and windblown loess (silt) deposits in upland areas along stream systems. Bedrock beneath the facility is composed of alternating sequences of limestones and shales of the Kansas City Group within the Pennsylvanian System.
Depth to bedrock at the site ranges from nine to 31 feet below ground surface (bgs). Soil beneath the facility is a lean clay exhibiting a hydraulic conductivity of 9.4 by 10.6 centimeters per second. The material in the excavation area consisted mostly of clays of medium plasticity.
The facility is approximately 0.6 miles northwest of the Verdigris River and 0.9 miles northeast of the Fall River. Depth to groundwater at the facility is approximately 10 feet bgs. Due to the operation of a previously installed remediation system, groundwater flow at the site is south toward the groundwater treatment system.
Regulatory History
Contamination associated with the former dry cleaning facility was first identified in 1996 during groundwater investigation activities associated with an adjacent refinery site approximately 0.5 miles west of the facility. Analytical results collected from a refinery monitoring well identified concentrations of chlorinated solvents. KDHE subsequently performed groundwater probing activities near the facility, which identified PCE at concentrations above the U.S. Environmental Protection Agency (EPA) maximum contaminant level (MCL). A subsequent Environmental Site Assessment indicated that concentrations of PCE and trichloroethylene (TCE) were above MCLs in groundwater samples. A contaminant plume approximately 1,000 feet downgradient of the site was identified. (See Figure 2.)
In 2003-2004, a groundwater treatment system was installed at the facility to treat groundwater impacted by the chlorinated solvents. A site investigation and supplemental source investigation were conducted by Burns & McDonnell in 2007 and 2008, respectively, to identify the extent of subsurface soil contamination in the source area. Burns & McDonnell determined that the majority of the PCE-related source area soil contamination was beneath the northeast corner of the building in the vicinity of the former dry cleaning machines.
Preconstruction/Pre-Excavation Activities
Before starting on-site activities, the team obtained a City of Neodesha Building and Flood Plain Development Permit for project building and demolition activities. To ensure safe working conditions for building tenants, site managers and subcontractor personnel, a Burns & McDonnell structural engineer conducted an evaluation of the building to determine critical load structural points and provide guidance for installation of a temporary structure-support framework.
At a project kickoff meeting on Oct. 12, 2009, KDHE, RSI and Burns & McDonnell met with building tenants and city officials to review the scope of work and introduce all parties working on the project. To minimize business interference, a staging area for temporary storage of all project-related equipment and supplies was set up in a low-traffic parking area immediately west and southwest of the facility.
Steps to Minimize Disruption
To further minimize disruptions, additional activities were conducted prior to the start of source-area remediation. To provide sufficient access for soil excavation activities, the two dry cleaning machines in the rear of the facility were disconnected from utilities and removed from the facility after the north wall had been disassembled. Additionally, an outbuilding that contained a commercial water heater and a boiler was permanently demolished. The water heater was replaced and relocated within the facility and the boiler was removed from the site as it was no longer needed. Removal of the outbuilding and equipment allowed easier access to the excavation area.
Prior to excavation activities, active utilities that could be affected by the excavation and were considered a safety issue were rerouted. Rerouted utilities included gas, water, steam, sanitary sewer lines, and electric lines associated with the former dry cleaning and washing machines. The rerouting was conducted in such a way that impacts to the laundromat operations were minimal.
Before demolition and excavation began, all interior furnishings, equipment and flooring in the excavation area were relocated and stored. Once utilities were rerouted and interior furnishings relocated, the back area of the facility was temporarily closed for business and demolition and excavation preparation activities began.
Remediation Design Protects Facility Occupants
Controlling the migration of fugitive dust and vapors from the excavation area to the rest of the facility was a major health and safety requirement. Temporary walls, covered with plastic sheeting, were constructed and installed around the perimeter of the excavation. Existing interior walls adjacent to the excavation were reinforced with one-inch plywood for protection and were covered with plastic sheeting to mitigate the migration of dust, vapors and excavation debris into the occupied portions of the facility. Facility ventilation ducts and vents were closed and sealed to prevent dust from entering the ventilation system. Air monitoring using a photoionization detector (PID) was conducted during excavation activities in the occupied portions of the facility. Based on the safeguards implemented during remedial work at this facility, at no time during the excavation activities were elevated concentrations of vapors encountered within the occupied sections of the facility.
A temporary engineered support structure was installed to secure the building frame prior to beginning the excavation work. Installation of the temporary support structure included steel I-beam support columns and shoring beams, base plates and timber cribbing for shoring load distribution to the floor slab and the addition of angle braces for temporary bracing. Contractor and field personnel continually monitored the shoring installation to assure the integrity of existing structural systems. As a result of Burns & McDonnell's engineering assessment and RSI's structural support installation, no damage resulted to the building frame.
Demolition Procedures
Two interior walls within the excavation area of the building were removed to accommodate excavation activities. A temporary wall was constructed to separate the excavation area from the occupied portion of the facility. A portion of the eastern wall of the facility was also removed and a temporary security wall containing a metal door and lock was installed to provide limited operation and maintenance access to the laundromat during the excavation activities. The temporary walls were also covered in plastic sheeting, again to minimize dust in occupied areas.
After construction of the temporary walls and construction entrance, the existing concrete slab covering the contaminated source area was saw-cut to separate it and was removed for off-site disposal as construction debris. During the visual utility inspection of the sub-slab material, two effluent water lines were discovered and relocated without impacting the project schedule.
Following removal of the subsurface sewer lines leading to the former sewer sediment basin, the sewer basin was drained as much as possible and the sediments in the basin were transferred to 55-gallon drums. Ambient air screening, using a PID, recorded volatile organic readings in excess of 10 parts per million (ppm) during the removal of these sediments. Per safety guidelines, the excavation work ceased and subcontractors upgraded their personal protective equipment to Tyvek suits and respirators. After the contaminated sediments were removed, the sediment sewer basin was decontaminated by pressure washing, broken down into manageable pieces, and disposed as construction debris. On-site decontamination of the basin significantly reduced KDHE's special waste disposal cost.
Excavation Activities
The excavation of contaminated soils was completed within five days in October 2009. Soil excavation activities were performed using a mini-excavator, which allowed for interior excavation, produced a smaller footprint and allowed surgical removal of impacted soils. The excavation was approximately 25 feet by 25 feet (see Figure 3) and a minimum of four feet in depth, with the deepest portion of the excavation reaching the water table at approximately nine feet bgs. To determine if the excavation had reached the limits of the soil contamination, soil samples were collected and analyzed by an on-site laboratory equipped with a gas chromatograph (GC) capable of analyzing for PCE, TCE, and cis-1,2-dichloroethylene (cis-1,2-DCE). Using an on-site laboratory enabled Burns & McDonnell to achieve results within 30 minutes of sample collection and allowed for segregation of excavated soil for off-site disposal options (hazardous or non-hazardous). This provided a more accurate assessment of soil classification for disposal and reduced disposal cost.
Approximately 200 tons of contaminated soil were removed from the excavation, of which only 55 tons were classified as hazardous waste. Most of the soils classified as hazardous waste were removed from the vicinity of the former sediment basin, which was determined to be the primary source of chlorinated solvent contamination. Soil removed from this area had PCE concentrations up to 140 million µg/kg, TCE concentrations up to 4.3 million µg/kg, and CIS -1,2-DCE concentrations of up to 1 million µg/kg.
Post-Soil Removal Construction Activities
When soil removal was complete, well-graded and compacted three-inch crushed stone was used to backfill the excavation. Prior to pouring the replacement floor, an additional four- to six-inch layer of half-inch crushed stone was emplaced to provide a base for the concrete floor slab. This layer was placed on top of the three-inch crushed stone and compacted using a walk-behind plate compactor.
Utilities including a new sewer basin, floor drain, sanitary sewer lines and overhead natural gas line were reinstalled. A new eight-inch-thick concrete foundation was poured to match the existing foundation of the building and a footing for the primary support column was installed. New ¾-inch anchor bolts were placed in the concrete footing to secure the existing building frame base plate to the new foundation.
After sub-slab utilities and structural supports were installed and the backfill material properly compacted, a 6-millimeter vapor barrier was placed over the backfill, directly below the new concrete floor slab. The replacement concrete slab and sidewalk were poured to match the existing concrete thickness. The new slab was connected to the existing slab using two-foot sections of number three rebar that were doweled into the existing slab every one foot (off-center) and was reinforced with welded wire fabric. The slab was installed following American Concrete Institute standards.
Interior facility restoration activities included restoration of interior walls and structural supports, reinstallation of utilities, flooring and internal furnishings and installation of a new ceiling grid. Exterior facility restoration activities included new siding and paint, landscaping with new grass and vegetative cover, final grading, and gravel driveway restoration. Upon completion of excavation activities, a new exterior wall was constructed in the original location of the west wall.
Conclusions
Based on laboratory analysis of soil samples collected during the excavation, the source area for chlorinated solvent contamination at the facility was considered remediated. Soil removal was conducted with minimal facility-operation downtime and no health and safety incidents. Soil removed from the source area had PCE concentrations of up to 140 million µg/kg, TCE concentrations of up to 4.3 million µg/kg, and cis-1,2-DCE concentrations of up to 1 million µg/kg. Removal of the contaminated soil from beneath the existing facility produced the following benefits:
- Reduction of risk to building inhabitants
- Minimal business downtime during remediation
- Removal of a source near a public school
- Reduction of the source of the PCE groundwater plume that has migrated off-site (thereby allowing the currently installed groundwater treatment system to effectively address and reduce the remaining groundwater plume)
- Reduction of the overall remediation time frame for the facility
Following remedial and restoration activities, the facility returned to full normal business activities. Removal of contaminated soil did not require demolishing the entire structure, and disruption to building tenants was minimized.
About the Authors
Walter McClendon, PG, is an associate hydrogeologist in the Burns & McDonnell Environmental Group.
Martha Hildebrandt, PG, is a senior geologist in the Burns & McDonnell Environmental Group.
Tim Stecher, PG, is a senior geologist in the Burns & McDonnell Environmental Group.
Grant Sherwood is president of Remediation Services Inc.
Scott Yankey is manager of the Landfill & Dry Cleaning Remediation Unit of the Kansas Department of Health and Environment.
