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A Phase II Site Investigation may be required to complete "all appropriate inquiry" with respect to Superfund liability or may be triggered due to a spill or a hazardous material or petroleum product. A Phase II Site Investigation is typically an intrusive investigation including evaluation of the extent and magnitude of contamination in soil or groundwater on a property where there is a known or likely presence of contamination based upon preliminary data; however, Phase II activities could also include evaluation of contaminant concentrations in sediment, surface waters or buildings.

Although the sources of contamination may vary, the key to successfully evaluating the significance of or mitigating environmental impacts is understanding the "big picture". At StoneHill we specialize in comprehensive site investigation practices that are designed to take advantage of both traditional investigation methods and new technologies and methods to develop a comprehensive site investigation to meet the specific needs of the client, the environmental regulations governing the project, and potential uses of the property. After determining the nature and extent of the contamination on a site and with a full understanding of the history of a site, the subsurface soils, groundwater table elevation and gradient, current conditions, current and future exposure pathways, as well as a superior understanding of the real world risks posed by the Site, StoneHill can then tailor future response actions to best meet the many interests involved with a property.

StoneHill's staff has experience conducting Site Investigations at various petroleum contaminated sites including gasoline, diesel, fuel oil, No. 6 fuel oil, mineral spirits, and mineral oil dielectric fluid sites. Additional experience includes work at polychlorinated biphenyl (PCB), metals including arsenic, chromium and lead and chlorinated solvent (DNAPL) sites in both bedrock and overburden. Knowing the various physical and chemical characteristics of numerous contaminants, StoneHill can customize the investigation methods to assure appropriate sampling methods are employed and sampling locations chosen. StoneHill's investigation methods are deductive, with initial activities driving the activities conducted in the latter stages.

StoneHill has extensive experience with both traditional and innovative subsurface exploration including overburden and bedrock drilling and sampling using hollow-stem auger, air rotary, fluids rotary, roto-sonic, direct push, and horizontal well installation technology. In addition, StoneHill has used surficial geophysical investigation technology such as seismic refraction and ground penetrating radar among others, as well as down-hole geophysical tools to electronically test the subsurface. Other in-situ stratigraphy testing technology used by StoneHill includes cone-penetromater testing.

In addition to investigation, StoneHill is familiar with traditional methods of sampling soil, water and air including split spoon soil sampling, test pit sampling, ground water monitoring wells, surface water sampling, sediment sampling and time weighted water and air samples. StoneHill is also practiced in more innovative sampling methods including ground water and soil diffusion samplers, infrared down-hole samplers, real time colorimetric sampling systems, and dedicated horizon samplers.

Selected Project Summaries

Commercial Property, North Conway, NH

StoneHill is currently managing the monitoring and cleanup of No. 6 oil impacted groundwater and soil at a lodging facility located in North Conway, NH. In 1999, a 10,000 gallon leaking underground storage tank (UST) was removed from the subject property. For an undetermined amount of time,
No. 6 oil leaked through a 4-inch diameter hole in the bottom of the UST. Based upon information collected during site investigation activities, including the advancement of soil borings and installation of groundwater monitoring wells, it was determined that the No. 6 oil had migrated vertically down to the groundwater table forming a thick free product lens and a thin floating layer of oil migrated slowly in the direction of groundwater flow 300 feet downgradient of the release area. Soil borings revealed soils impacted with No. 6 oil from 10 to 35 feet below the ground surface and monitoring wells contained free product oil thicknesses of one to twelve feet. StoneHill is currently evaluating remedial alternatives to effectively recover No. 6 oil from the recovery wells.
Former Pig Farm, Central MA
The farm property study area encompasses a 62-acre property formerly used as part of a farm homestead, apple orchard, saw mill, and pig farm since 1910. During the 1970's and 1980's on-site burial of debris/farm waste took place at several locations on the property and 55-gallon drums containing waste paint were disposed in an on-site gravel pit. Contaminants of concern at the Site included arsenic in soil and stream sediments, polynuclear aromatic hydrocarbons in surface soils, waste oil in soil, waste paint in soil, and lead in soil. StoneHill conducted a Massachusetts Phase II Comprehensive Site Assessment which included numerous tasks including a detailed review of readily available historical aerial photography, collection of
numerous surficial soilsamples and sediment samples both on site and off site to assess background soil and sediment quality; installation of overburden monitoring wells and shallow bedrock monitoring wells, collection of several rounds of groundwater and surface water elevation data to assess groundwater flow directions and its interactions with surface water; and collection of comprehensive rounds of groundwater samples for laboratory analyses. A key component of the site investigation was the reliance on indicator compounds, which significantly reduced overall analytical costs. Additionally, using specialized analytical techniques, much of the soil identified as containing PAHs, was found to be impacted by wood ash from the on site burning of waste wood. The elevated arsenic concentrations found in soil and sediment were also found to be the result of natural arsenic being mobilized and re-precipitated as natural groundwater chemistry varied. These findings resulted in a significant reduction of the cost of completing the necessary response actions and a Class A-2 Response Action Outcome (RAO) Statement was filed with the MADEP.

 

 

600 State Street, Suite 2
Portsmouth, NH 03801
Telephone: 603-433-1935
Toll Free: 1-800-639-4503
Fax: 603-433-1942
info@stonehillenvironmental.com

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