Site Maintenance & Monitoring Projects
New Mexico Leaking UST Sites
INTERA was awarded nine contracts to conduct quarterly monitoring at District II leaking UST sites. All of the sites, located throughout northern New Mexico, have groundwater impacted by petroleum hydrocarbons from leaking USTs. Initially, we performed well reconnaissance surveys to determine the number of existing wells and the level of effort necessary for the quarterly monitoring events. During the well surveys, we determined that there were approximately 140 monitoring wells to be sampled quarterly. The sampling events were performed consecutively over a two- to three-week period. Groundwater samples were analyzed for volatile organic compounds and natural attenuation parameters at each well location. INTERA performed data review and analysis of the analytical data to evaluate the nature and extent of petroleum hydrocarbon impact, and whether natural attenuation processes are acting to remedy the contamination. In addition, we have decommissioned remediation systems at several sites. We have also performed maintenance activities at the sites including replacement of well vaults at the monitoring wells, removal of PVC piping associated with a remediation system, surging of monitor wells that are inadvertently plugged, connection of a residents water supply to the municipal water supply system, and additional routine maintenance activities.
Treatment System O&M
Under two large, multi-site, state-lead engineering/remediation and general services contracts, INTERA provided a wide variety of monitoring and maintenance services at dozens of sites contaminated by leaking petroleum storage tanks located in west and central Texas. Services provided through these contracts included system installation and optimization, system O&M, and reporting. INTERA improved the performance of existing groundwater pump-and-treat systems at 13 sites. Activities included connecting additional recovery wells to the remediation systems to increase contaminant removal, and upgrading equipment and system design to increase system efficiency. We were also responsible for the O&M of remediation systems at 13 PST sites. Activities at these sites included ensuring that systems were operating at peak efficiency, collecting influent and effluent samples to monitor system performance, performing repairs and upgrades to the systems as required, and replacing expendable system components such as carbon canisters and filters. INTERA produced a variety of reports for the PST sites including monthly status and product recovery reports, quarterly groundwater monitoring reports, Plan A Investigation Reports, Site Closure Reports, receptor surveys, and letter reports outlining specific recommendations for optimizing remedial systems.
Chemical Production Facility
Past production and handling of an arsenic-based herbicide had resulted in arsenic contamination of the groundwater beneath an industrial plant site. The contaminated water was, in turn, discharging to an adjacent waterway. Through the use of a three-dimensional groundwater flow and transport model, INTERA evaluated a number of potential remedial measures including the installation of a sheet-pile barrier wall, a system of infiltration trenches, and a network of injection and extraction wells. After we determined the most hydraulically-effective system, a network of extraction wells and a groundwater treatment system were installed by another company. After the system failed to meet containment and cleanup expectations due to improper construction and operation, INTERA was retained to remedy the problems with the extraction system and increase the efficiency and performance of the system. In effect, we took the system through its “shakedown” phase, which had never properly been done when the system was first installed, and made the system fully operational. We retrofitted all the extraction system components, installed additional extraction wells, and added an in-line pH adjustment capability to prevent the precipitation of silica in the extraction lines. INTERA also implemented a proactive preventive maintenance program to ensure that the groundwater extraction system will continue to function at a high level of efficiency.
Characterization & Monitoring of Landfill Gas
INTERA was retained by the City of Albuquerque (COA) to characterize the nature and extent of landfill gas (LFG) contamination at seven former landfills located throughout the city. The former landfills were filled with municipal waste during various periods from the early 1960s until the early 1980s. Previous investigations by the COA identified LFG being generated through the decomposition of waste. The primary LFG constituent of concern is methane. Our scope of work includes characterization of the nature and extent of LFG contamination through the drilling, installation, and sampling of LFG monitoring wells. LFG monitoring well design and completion for each of the monitoring wells consists of multi-level gas sampling probes. Each of these probes is sampled to monitor LFG for methane, carbon dioxide, oxygen, nitrogen, and hydrogen sulfide. A total of 160 landfill gas wells, with three probes installed in each well, have been installed to date and are actively being monitored by INTERA staff.
