Request for Proposal s69

Remedial Evaluation and Strategy Development

PCB-Containing LNAPL and Dissolved-Phase Groundwater Plume

for

ABC Chemicals

Ontario, Canada

Project Background

The ABC Chemicals Breslau facility is an oil re-refinery operated by various owners since the 1960s. Waste oil originating at a former lagoon that was closed in 1977 has been thoroughly investigated and identified to be present on the shallow water table at the facility and on the adjacent property owned by GravEx Limited. The waste oil, which occurs as separate phase product floating on the water table, is referred to as light non-aqueous phase liquid (LNAPL). The LNAPL extends from the facility onto the GravEx property a distance of approximately 150 meters. The LNAPL consists of viscous petroleum hydrocarbon oil that contains low concentrations of PCBs and other chlorinated solvent compounds. The concentration of PCBs measured in the soil ranges from <0.01 to 21.4 parts per million (ppm), while the oil itself has a PCBs content ranging from 75 to 340 ppm.

The GravEx property is hydraulically downgradient of the site with respect to the direction of groundwater flow. GravEx operates and dewaters a large open-pit aggregate (gravel) mine about 300 meters downgradient from the LNAPL. The gravel pit extends nearly to the edge of the Great River located about 700 meters from the LNAPL. Two inactive municipal water supply wells are located in the floodplain of the river, between the aggregate mine and the river. The wells have not been in use by the municipality since about 1993 but will be reactivated in 2007. The wells are designed for induced infiltration of river water and are estimated to withdraw 80 percent river water and 20 percent groundwater. The mine-pit dewatering rate is roughly equivalent to the extraction rate of the two municipal wells at about 2 million cubic meters per year. Mine dewatering has lowered the water table in the vicinity of the pit about 8 meters, and about 2 meters in the vicinity of the LNAPL compared to pre-mining water levels. Elsewhere in the vicinity, land use is agricultural.

The shallow groundwater system at the site consists of upper and lower sandy aquifers approximately five and 15 meters thick separated by a less permeable clay till aquitard about 10 meters in thickness. A downward vertical gradient exists between the two aquifers. The upper aquifer pinches out just downgradient of the LNAPL. The municipal wells near the river are installed in the lower aquifer. Dissolved constituents in groundwater associated with the LNAPL are observed primarily in the upper aquifer and occur at low concentrations in a “halo” of relatively limited extent near the LNAPL but that diminishes rapidly a short distance away. Dissolved constituents in the lower aquifer are less prevalent, occur sporadically and at lower concentrations, and similarly do not exceed MOE criteria beyond a distance of about 80 meters from the LNAPL based on the most recent data. Nearer the river, no contaminants were detected in four Regional Municipality of Waterloo sentry wells located between the gravel pits and inactive municipal wells sampled in April and September 2001.

Although recoverable free product occurs in the source zone on the ABC Chemical property, the current overall condition of the LNAPL is one of a static plume. Visual comparison of historical contaminant plume maps indicates that the extent of the LNAPL has not changed significantly in eleven years. The LNAPL is effectively contained by its limited mobility due to high viscosity in the source zone, near residual saturation levels at the distal end, geologic control associated with a trough is an underlying aquitard, and a seep collection system operated by ABC Chemicals at the toe of the plume since 1992.

Scope of Work

There is no direct pathway between the residual LNAPL and the inactive water wells near the Great River. However, the municipality is not convinced that their municipal wells are risk free from potential future impacts associated with the migration of dissolved phase constituents in groundwater. The municipality has requested that the Ontario Ministry of Environment require ABC Chemicals to remove the LNAPL and all residual saturated soils by excavation. In preparation for responding to MOE comments ABC Chemicals is interested in pursuing one of the following approaches.

1. Prepare and cost different excavation and treatment options for the LNAPL and provide ABC Chemicals a recommendation on the least expensive approach should MOE require LNAPL removal. These are excavation and treatment options only. Do not include any in-situ treatment options (e.g., steam injection) or partial product recovery options (e.g. product pumping or biodegradation). Include excavation and offsite disposal (landfilling) [if appropriate], excavation and offsite treatment, and excavation and onsite treatment. List key assumptions.

2. Prepare and cost a contingency approach for preventing a potential dissolved phase plume from reaching the municipal wells by evaluating and discussing several alternatives. Since this is the municipality’s key concern, a solid plan to mitigate any potential impact to the wells from dissolved constituents may convince them to back away from the costly LNAPL excavation. This is to be focused on the potential migration of constituents dissolved in groundwater, not the LNAPL. Possible options may include for example, pump-and-treat, slurry walls, air sparge curtain, in-situ chemical oxidation, etc.

3. Prepare an evaluation of the potential fate and transport of the dissolved phase constituents from the vicinity of the plume to the area of the municipal wells. The idea here is, if results are favorable, to convince the municipality that concerns over impacts to the municipal wells are unwarranted based on the hydrogeologic setting, groundwater flow, well characteristics, and fate and transport properties of constituents. Consider potential migration of constituents though the aquitard and the effects if the water table elevation changes after mine dewatering ends.

Additional site data will be provided to facilitate the above evaluations.

Contacts

All inquiries and documentation should be directed to either the Brian Martinek at Cameron-Cole 303-938-5530 ().

For Educational Purposes Only