Phase III RCRA Facility Investigation and Groundwater Quality Assessment Report
This site is regulated under the federal Resource Conservation and Recovery Act (RCRA), with oversight delegated to Alabama Department of Environmental Protection (ADEM). The site has contaminated groundwater in both the overburden and the bedrock, and local occurrences of non-aqueous phase liquids. The bedrock is predominantly dolomite, having sparsely distributed solution conduits characteristic of geomorphically immature karst. The solution conduits locally accelerate groundwater flow velocities. The groundwater quality assessment focused on organic compounds, metals, ammonia, and sulfate. Installation of offsite perimeter wells involved extensive negotiations with property owners, including mining companies, metal tube manufacturers, and railroad companies. Loose overburden conditions made the drilling difficult. ADEM required comparison of the groundwater quality results with five sets of screening criteria:
(1) concentration limits specified in the site RCRA permit.
(2) federal Maximum Contaminant Levels.
(3) federal Secondary Maximum Contaminant Levels.
(4) EPA Region IX Preliminary Remediation Goals.
(5) background concentration data from the earlier Phase I and II RCRA Facility Investigations (RFIs).
- Negotiations with offsite property owners were sometimes difficult, but in all cases resulted in signed agreements allowing the installation and monitoring of new wells.
- There are extensive areas and volumes of primarily man-made fill, comprising rock fragments, coke, coal, sand, and s lag. Drilling required the use of Odex-type rigs, which advance casing simultaneously with the drill bit (to avoid possible downhole migration of contaminated water). Drilling through the overburden required pounding in temporary, large-diameter casing.
- Contaminants may be directly released into the groundwater from leaching of the man-made fill that comprises very extensive parts of the overburden.
- There are extensive historic and current up-gradient, offsite sources of most site-related contaminants.
The Interdisciplinary Approach
ADEM sent the client a Notice of Deficiencies letter regarding the site, followed by a letter addressing Permit Required Corrective Action Plan Deliverables. These documents required the client to conduct a Phase III RFI. ADEM additionally requested a new perimeter well array having three- or four-well clusters with specified locations, depths, and telescoped construction. We developed the Phase III RFI workplan, which was approved by ADEM. Comparisons of the groundwater chemistry results were made with five different regulatory categories of groundwater protection standards or benchmarks.
The Sustainable Result
- Demonstration that no site-sourced contaminants were detected on the down-gradient side of the local base level stream. However, site-related contaminants discharged to this stream, which derives significant base flow from groundwater seepage.
- Demonstration that site-derived contaminants rapidly attenuated down-gradient to concentrations which, in most cases, were below some of the groundwater protection standards under consideration.
- Proposed groundwater protection standards that are most applicable to the site. For some constituents, compliance was shown to require application for Alternate Concentration Limits.
- Formal acknowledgment by ADEM that the horizontal and vertical limits of contamination had been satisfactorily determined.
- Installation of paired shallow and deep perimeter monitoring wells to evaluate if groundwater contaminants had migrated offsite – the site is a former coking facility.
- Slug-testing analysis of all perimeter wells.
- Development of site conceptual model for groundwater flow and contaminant fate and transport.
- Two quarterly monitoring events to measure well groundwater levels and analyze water chemistry.
- Demonstration that concentrations of coke and petroleum-related organic compounds (total BTEX and total PAHs) was nondetect to extremely low.
- Demonstration that many of the site-related contaminants can be derived from leaching of coke and coal fill in the overburden, as opposed to being solely derived from former facility leaks and spills. Man-made fill occupies very large volumes of the overburden both offsite and onsite.
- Recommendations to develop Alternate Concentration Limits for certain site-specific groundwater protection standards, and to shift the focus of long-term groundwater monitoring to the perimeter well network.
- Negotiations with Alabama Department of Environmental Protection (ADEM).