Environmental Monitoring Plans (EMP's) are required under federal regulations cited in 40 CFR Part 258 and State requirements from the Annotated Code of Maryland 26.04.07 which details gas, ground-water and surface-water monitoring protocol. These regulations are in place to ensure that any water quality data gathered at landfill sites is sufficient to draw valid conclusions regarding the potential impact on human health and the environment. On July 3, 2000 and August 9, 2010, the Maryland Department of the Environment approved the Environmental Monitoring Plans (EMP's) for the closed St. Andrews and Clements Landfill facilities, respectively. The EMP's also incorporate the initial MDE-approved Water Quality Monitoring Program for both the closed St. Andrews and Clement’s Landfills dated September 16, 1996. These programs are just a part of the Federal / State mandated 30-year post-closure care requirements.
Monitoring must be performed during the active life of a landfill, during the closure and post-closure periods. Following closure of every municipal solid waste landfill the owner/operator is required to conduct post-closure care for a period of thirty (30) years. Post-closure care consists of maintaining the integrity of the final cover and maintaining the groundwater, gas and leachate collection systems. At the end of the post-closure period an independent professional engineer must certify completion to the State.
Ground and Surface Water Quality Sampling
The Maryland Department of the Environment performed the semi-annual “Detection” Monitoring and sampling events from 1982 to 1991. Since that time, the County has been held responsible for developing and implementing their own State-approved program. Detection Monitoring data is required to be statistically evaluated with respect to background concentrations and regulatory standards. If the statistical test results from the Detection Monitoring events identify a statistically significant increase (SSI) over the background data for one or more constituents, the owner of the facility is required to initiate “Assessment” Monitoring. The water samples collected during the semi-annual detection monitoring events are tested for Appendix I constituents which consist of 15 total metals and 47 volatile organic compounds (VOCs). This type of sampling includes but is not limited to: field documentation, well inspection, water level measurements, well purging, sample collection, equipment calibration / decontamination, special handling procedures, data validation, QA/QC sampling, chain-of-custody, statistical lab analyses, data validation and submission of reports to the state.
Assessment of Corrective Measures (ACM) In accordance with federal regulations cited in 40 CFR Part 257.26, the Maryland Department of the Environment (MDE) may also require an ACM be conducted for a site based on the environmental monitoring results. If, during the monitoring, any constituents (listed in Appendix II of 40 CFR Part 258) have been detected at a statistically significant level exceeding the ground-water protection standards, the law requires the owner / operator to initiate and complete an ACM within a reasonable period of time. An ACM evaluates the environmental monitoring results, site conditions, alternative remedial actions, the respective costs, performance and reliability data, ease of implementation, potential impacts of the potential remedies ( ie. safety impacts, cross-media impacts, potential for residual contamination, etc. ), the time required to begin and complete the remedy and an analysis of short and long term effectiveness. Once all of the remedial action alternatives are evaluated, a recommendation is forwarded to the State for approval and eventual construction, subject to all State or local permit requirements or other environmental or public health requirements that may affect implementation of the remedy(s).
The results of the Detection Monitoring events in 1997 and 1998 identified VOC contamination in the uppermost water table acquifer that was attributable to the St. Andrews Landfill. Assessment Monitoring events conducted in December 1997 and March 1998 revealed no concerns with regard to Appendix II constituents. However, a total of six (6) new and two (2) replacement monitoring wells were added to the existing network. At present, the monitoring well network around the St. Andrews Landfill consists of 12 ground-water monitoring wells and 3 surface water sampling points. The Health Department has tested down-gradient residential drinking water wells and has found the water in their wells to be safe for human consumption. Nonetheless, the County is moving into the Corrective Action Phase which relies heavily on the final capping and closure of the five (5) landfill cells in Area B at St. Andrews.
There are several locations in St. Mary’s County that were historically used as public “dump sites”--some on private and some on public properties. The DPW&T took the initiative in 2000 to begin the process of systematically assessing the sites located on County-owned properties. The general purpose of the assessment process is to evaluate the property for possible future use and to ensure that each site is generally free of any migrating contaminant levels exceeding State standards. In short, a series of test pits are dug with a back-hoe (under an approved OSHA Health and Safety Plan) to determine the limits of any waste material(s) that may have been deposited on-site. Both the horizontal and vertical limits are then surveyed and mapped for the permanent record. Independent contractors also collect and analyze groundwater samples extracted from around the perimeter of the site using a hydro-punch or other similar collection technique. In addition, any adjacent / down-gradient surface water(s) are also tested. This testing includes any “nearby” residential drinking water wells which are tested by the Health Department to ensure the well water continues to be potable and safe for drinking. To date, the DPW&T has completed assessments at the Ridge and Oakville Convenience Center sites. Individual assessments can take 10-18 weeks to complete at costs of between $15,000 and $23,000 depending on the size of the site. The information gathered is not required per State regulations however, DPW&T feels the environmental assessments are crucial in evaluating any potential risks the former public “dump sites” may pose to our community.