Large Scale General Construction, Groundwater Extraction and Remediation, Bedrock Drilling
Project Name: Hazardous Waste Landfill
Client: Government Agency
Location: Up-State, New York
Impact Characterization: The subject Site is a class 2 inactive hazardous waste disposal site located within a 19.6-acre permanent easement obtained by the regulatory agency. The Site was reportedly involved in salvage/ disposal of industrial fluid waste from 1952 to 1968. The site was later utilized as a waste oil transfer station. These activities resulted in the disposal of hazardous waste, including solvents, waste oils, polychlorinated biphenyls (PCBs), scrap materials, sludges, and solids at the site during its period of operation. The unlined nature of the landfill resulted in contaminant releases to the surrounding areas, including into the local bedrock aquifer occurring beneath the subject site.
The regulatory agency retained an engineering firm to provide design services related to the remediation of the project site. In order to obtain information necessary to complete the design of the final remedial alternative for the site, an investigation of the off-site bedrock aquifer needed to be completed. To accomplish the bedrock study site facilities/infrastructure needed to be designed, constructed and maintained.
Additionally, services were needed to manage the handling, transportation and subsequent off-site disposal of extracted groundwater and leachate collected from the previously installed (by others) on-site leachate collection system.
Technical Overview: PES was tasked with providing the oversight engineers with construction, field management and remedial services. The principle features of the work to be performed by PES included:
Installation of a gravel access road with turnaround and main entry gate/fencing within the subject Site;
Installation of a frac tank and associated appurtenances;
Clearing and removal of trees and other site preparation activities;
Installation of one new bedrock extraction well;
Installation of three electric piston extraction pumps and associated electrical equipment on one new and two existing bedrock extraction wells;
Installation of over 3,500-feet of double-walled, High Density Polyethylene (HDPE) piping system and associated appurtenances; and
operation and maintenance of the installed off-site pumping system.
PES began the project by first installing the access road and turnaround at the site in August 2007. The timing of this construction aspect was such that it allowed implementation of the required work in ideal (dry) weather conditions. This was essential considering the access road was to be installed over top of a previously installed clay cap.
The completion of this particular phase of the project was also scheduled first as it provided a staging area for the additional site work.
Once the roadway and turnaround were complete the base for the frac tank was completed in the same fashion and the frac tank was placed at the site. Completing the access road allowed for the staging of materials and other construction equipment necessary to efficiently complete other critical work tasks.
To allow off-site access to existing and newly installed bedrock extraction wellhead areas, PES cleared approximately 700 linear feet of wooded terrain and installed an improved access road consisting of shale bedding material. Once access to the drilling area was achieved the installation of the bedrock extraction well commenced.
Bedrock extraction well installation procedures involved the construction and installation of temporary decontamination facilities, drilling through approximately 85-feet of unconsolidated overburden material and setting a 12-inch steel surface casing in competent bedrock, all of which was completed by Aquifer Drilling and Testing, Inc. (ADT) with geotechnical oversight performed by PES. During the well drilling/installation process, PES geological staff collected 240 feet of continuous HQ rock cores. The resulting small diameter rock core borehole was subsequently reamed out to achieve the final designed borehole diameter of 9-7/8-inches. Six (6)-inch diameter PVC well screen and riser were installed to complete the extraction well to design specifications.
In an effort to expedite overall progress on the project, PES commenced the installation of the double-walled HDPE piping beginning in the landfill while simultaneously completing the installation of the extraction well.
Installation of the HDPE piping involved joining the pipe by thermal butt-fusion to produce a homogenous, sealed, leak tight system. PES personnel involved in the pipe fusing process were specifically trained by factory representatives to ensure high levels of QA/QC.
To document the integrity of the installed subsurface utilities and to ensure that piping and fittings were tight, all piping, valves and fittings were pressure tested in sections as the work progressed. In addition, completed respective utility runs were tested in their entirety following full installation.
To accommodate various system components several precast concrete structures were placed in conjunction with the subsurface piping system(s). Three air release chambers, one valve vault and five electrical utility vaults were set at locations in accordance with design documents.
Following successful installation and testing of the piping system, subterranean vaults and appurtenances, three electric piston extraction pumps and corresponding control circuitry were installed in respective groundwater extraction wells.
The well discharge was then connected to the HDPE subsurface piping with stainless steel piping, valves and appurtenances.
Data loggers were then installed/utilized in five wells to allow for aquifer performance data collection. The secured data was used to establish/confirm physical parameters of the bedrock aquifer as well as accurately determine aquifer responses to active groundwater extraction.
Once active pumping commenced, PES personnel performed operation and maintenance of groundwater extraction activities and monitored water storage availability with respect to frac tank capacity. PES also coordinated(s) for transport and disposal of extracted groundwater and water accumulated within the on-site leachate collection system.
Site Progression Specifics: - PES and ADT performed a majority of the work, including all trenching, piping and well installation activities, utilizing properly trained and skilled personnel and equipment. When additional expertise within a particular field/service (i.e.; electrical) was required, subcontracting services were acquired by PES, whereby PES acted as general contractor with sole oversight responsibilities for work completed on the project. General contracting duties included subcontractor set up and payment, scheduling and on-site supervision of subcontractor field activities and the procurement of equipment and materials necessary to complete the project in a comprehensive manner. PES project management and on-site field supervisors ensured that the work was completed efficiently, on time, within budget and in accordance with the design specifications.
Major site construction activities commenced in August 2007 and were completed in October 2007. The pumping system was placed on-line in March 2008. Since start up, over 50,000 gallons of impacted groundwater have been extracted from the bedrock aquifer. PES continues to implement the off-site remedy through operation and maintenance of the groundwater pumping system(s). The implemented remedial action continues to produce valuable data for the engineering firm to facilitate the completion of their comprehensive site investigation and ultimately determine an effective long-term