Hazardous Waste Disposal Landfill
Western U.S.SERVICE Assessment, Remediation & Monitoring (ARM)
Groundwater Monitoring and Modeling
PROJECTS \ CASE STUDY
Hazardous Waste Disposal Landfill
Cameron-Cole has provided groundwater modeling services at a Subtitle C RCRA Facility Investigation (RFI)/ Toxic Substances Control Act (TSCA) permitted hazardous waste disposal landfill since 2003. Environmental reporting requirements at the site have included preparation of semiannual hydrogeologic data summary reports including statistical analysis of geochemical data using an intrawell control chart technique, preparation of semiannual TSCA data summary reports, preparation of annual groundwater flow velocity maps, annual groundwater flow and solute transport model recalibration, quarterly performance evaluation sampling (included with TSCA Report) and data management. Cameron-Cole also maintains an extensive data management and report database tool that allows for rapid and efficient data queries, computer modeling output analysis, and reporting. The current database for this site consists of over 300 water level measurement and groundwater sampling events that have generated over 1,000,000 data records since 1981. An extensive set of queries has been designed to allow for the generation of data summary tables and the presentation quality graphics in support of hydrogeologic reporting and modeling analysis. The groundwater flow and solute transport models were developed for this site in 2003. The numerical analysis tool developed was intended to serve as a practical aid in the design and maintenance of the existing groundwater monitoring well network and in tracking the fate and transport of any Constituents of Concern (COCs) at the facility. This model provided the technical justification for a modification to the facility operating permit that reduced the frequency of groundwater sampling from a semiannual schedule to an annual schedule. To date, COCs in groundwater including Volatile Organic Compounds (VOCs) have been detected and incorporated into the groundwater model. Both the groundwater flow and solute transport models are recalibrated on an annual basis for this site. The annual recalibration report provides a discussion of the site conditions and hydrogeology, the site conceptual model, revised input parameter rationale, recalibration of the groundwater flow and solute transport model, and solute transport simulations. The current and previous versions of the flow and transport model are based on an extensive review of site data describing hydrogeologic conditions and processes. The original model and its revisions follow industry standards and are based on a thorough hydrologic calibration by matching simulated water levels to multiple sets of observed water levels and matching simulated 1,1-DCE and 1,1,1-TCA concentrations to those detected at the facility. An ancillary purpose of the groundwater flow and solute transport model was to provide a quantitative tool for conducting hypothetical release simulations at regulated units to evaluate the effectiveness of the existing groundwater monitoring well network. The model also provides a technical basis for determining a reasonable groundwater sampling frequency for the groundwater detection monitoring program. Based on model simulations, the groundwater sampling frequency at this facility was reduced from semiannual to annual resulting in significant long-term cost savings.