Large Scale Subsurface Investigation, Remedial Feasibility Study, Design, Install, Operate and Maint
Project Name: Former - Major Oil Bulk Storage Facility
Client: Major Oil.
Location: Capital District, New York
Impact Characterization: The subject site and surrounding properties have been impacted by various petroleum fuels, including various grades of gasoline, fuel oil and kerosene. For clarity in the subsequent discussion - the source site is designated the site proper. Documented impacts resulted from former activities associated with the site proper that included operation as a major oil storage facility (MOSF). Initial off-site investigations discovered petroleum contamination impacts to the shallow soil and local groundwater regimes. Subsequent investigations conducted on the site proper indicated significant impacts including thickness of light non-aqueous phase liquid (LNAPL) that varies from 1 to 5-ft, high concentrations of dissolved phase constituents in groundwater and a substantial degree of adsorb phase contaminates residing in the local overburden material. Total impacted area covers approximately 2 acres.
Technical Overview: - PES was initially retained by a government agency to conduct a supplemental site investigation in an attempt to delineate and identify the source of petroleum-impacted groundwater discovered at offsite locations. PES drafted a work plan and secured off site access at two adjoining parcels of land that were identified as potential source areas from a critical review of Sanborn maps that were obtained as part of a phase 1 site assessment.
Following review and approval of the work plan by the NYSDEC and negotiation of site access with adjacent landowners PES commenced the investigation by installing nine (9) soil borings and seven (7) groundwater-monitoring wells. Investigative depths reached 24-feet beneath the relative ground surface. Soil borings and monitoring wells were installed utilizing PES’s direct push soil probe. PES geotechnical staff performed oversight and direction of all drilling activities including continuous macro core sampling. The results of this initial investigation concluded that significant impacts were present at the site proper. Hydrogeologic assessment data indicated the site proper to be hydraulically up-gradient of the Spare Room II. This information documented the site proper as the source location for the petroleum impact to the local groundwater. Initial findings documented LNAPL and dissolved phase contamination consisting of greater than 100ppm of total STARS list VOC’s detected in groundwater.
PES documented the findings in a comprehensive investigation report that concluded the site is tidally influenced from the adjacent Hudson River, local geology consisted of silt, sand and gravel underlain by black shale bedrock, groundwater flow was confirmed to flow off site and ultimately that the most likely source of the petroleum impacts documented in the area were a result of the property formerly utilized for Bulk Petroleum storage/dispensing. Recommendations included in the report included additional subsurface investigation work to further delineate the plume limits, contaminant profile and magnitude.
PES completed a work plan to perform the recommended supplemental subsurface investigation of the site proper that included the installation of additional SBs and MWs in a 40’X40’ grid pattern to complete a comprehensive assessment of subsurface conditions. The fact that the site previously possessed multiple possible sources in the way of underground/aboveground tanks and associated piping dictated the need for the detailed grid pattern-drilling program. Additional work tasks included a preliminary, private utility mark out, subsurface geophysical survey to ascertain the existence of USTs and piping that were depicted on a historical map of the former MOSF and a site survey that was completed by a NYS licensed land surveyor. The professional survey work was required to document accurate locations of installed monitoring wells, elevations and relevant surface features.
Upon approval of the supplemental work plan PES commenced additional investigative work by completing a private utility mark out on the property and then installing 82 soil borings and an additional 28 groundwater monitoring wells over the approximate 5-acre site.
The results of the investigation successfully delineated the limits of the contamination previously discovered and identified two additional areas of concern, in which significant (4-5-feet) of LNAPL were documented. Additionally, a subsurface geophysical ensued, in which an underground storage tank (UST) associated with former site operations was identified.
With the comprehensive site investigation completed a critical technical review was performed utilizing all available information collected from the site. The review focused on the three identified target areas of concern. Particular attention was paid to geological and hydrogeological data collected and a recommendation for pilot testing to determine the site-specific effects of high vacuum, total fluid extraction (HVTFE) was recommended. Authorization was granted and PES proceeded to complete the pilot test study to evaluate proposed remedial method feasibility and obtain preliminary bench-scale design parameters. The bench scale design data was subsequently used to develop a full-scale remedial corrective action plan using HVTFE as a cost-effective strategy for containment/reduction of the LNAPL and dissolved phase plumes.
For purposes of the pilot study five six-inch diameter wells were installed at various locations throughout the site. The remedial test wells were installed by Aquifer Drilling and Testing (ADT) in concert with PES geological staff supervision. ADT performed all required drilling using hollow stem auger methods coupled with continuous split spoon sampling procedures. ADT drilling staff was tasked with proper drilling, construction, design and development of the test remedial wells. In general test locations were selected due to their spatial relationship with respect to both existing (historic) monitoring points and the geographic occurrence within the documented plume. A vacuum truck was then utilized to create a vacuum within each pilot test well.
Testing involved variable vacuum application and stepped draw-down limits procedures. PES recorded all site-specific design data/parameters.
The results of the pilot test study concluded that the proposed remedial action would be capable of achieving the required design flow and vacuum at the site necessary to achieve site-specific remedial goals.
PES used the site-specific design data to develop a comprehensive corrective action plan (CAP) for the site, utilizing high vacuum total fluid extraction (multi-phase extraction) for mitigation of petroleum impacts. The plan summarized investigative and pilot test results, conceptual design of the remedial system and system and site monitoring plans. Associated project budgets and implementation schedules were developed as part of the comprehensive corrective action plan.
Upon receipt of CAP approval from the Department, PES/ADT implemented the CAP by installing 18, large diameter (four-inch) groundwater extraction wells in an array that covered areas of concern in the northern plume. In association with the 18 recovery wells, PES installed 2,000 (+) linear feet of subsurface piping at depths below the projected frost penetration. In addition, provisions were made to supply primary and secondary electrical service including a 25 KVA transformer sub-station and containment pad. The required remedial trenching generated approximately 400 tons of petroleum-impacted soil. PES arranged all aspects of the soil transport/proper disposal - including loading.
Once all remedial system appurtenances and electrical connections were installed a trailer-mounted HVTFE system consisting of two (2) 20-horsepower liquid ring vacuum pumps, moisture separator, commercial-grade coalescing oil-water separator, bag filtration units, low profile air stripper, granular activated carbon treatment and 500-gal aboveground storage tank (for recovered LNAPL) was installed at the site.
The remedial system was constructed in a trailer such that it can be mobilized to the three separate areas of concern that are to be remediated with a single site-specific remedial system.
In addition to governing system design, installation and operations, PES was also responsible for set up and coordination of site access through the property owner, electrical and discharge permits/service provided by the local municipality, procurement of building permit and attending public meetings.
Site Progression Specifics: - PES was involved at the inception of this large-scale investigation and remedial project and has successfully governed the course of the work to reach a point of active remediation to the benefit and satisfaction of the local regulatory community (NYSDEC) the responsible party and the local community (through public meetings, etc.)
The PES/ADT team performed a majority of the work, including all trenching, piping, well installation, UST closure activities and contaminated soil, storage, handling, transportation and disposal utilizing properly trained and skilled PES personnel and equipment. When additional expertise within a particular field/service (i.e.; electrical, geophysical and location/elevation survey, etc.) were 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 site-specific CAP.
Major site construction activities (remedial system installation) commenced in September 2007 and were completed in December 2007. The HVTFE system was placed on-line in March 2008. PES continues to implement the remedy through operation and maintenance of the system.
This work was performed under a time and materials contract with project budgets produced for major site events for the Department. Work for GPC has been completed subject to a comprehensive budget. PES/ADT have consistently performed required work within the time and budget framework for this site to the satisfaction of the client(s). When the responsibility of the project transitioned from the Department to GPC the Department representative stated “Precision Environmental Services did excellent work for the Department on a very complex site. I appreciate the way [PES staff] supervised the work done on this site and look forward to working with [them] and [PES] in the future.”