HETI has designed, installed and maintained a variety of site remediation systems at hundreds of locations. These systems have recovered, contained or destroyed in-situ hydrocarbon, other organic chemical, and metal releases in all stages - including separate phase, dissolved phase, adsorbed phase, and vapor phase.

Our staff stays current with the latest remediation technologies and innovations…and is experienced in the following techniques:

	Soil vapor extraction
	Air sparging
	Ground water extraction and treatment
	Product recovery
	In-situ oxidation
	In-situ reductive dechlorination
	Dual-phase extraction
	Bio-venting
	Excavation and disposal/treatment
	Bioremediation
	Oxygen sparging
	Monitored natural attenuation

We obtain the necessary permits required for the various phases of site recovery operations. Remediation equipment is purchased or leased, installed, and supported during the life of a project. Routine maintenance, where required, is scheduled to reduce operating costs to the extent practical.

HETI's extensive remediation experience helps to ensure that our clients' projects are completed on time, within budget, and with a minimum of problems.

Representative Projects *

Residential Fuel Oil Release (Massachusetts) – An oil release occurred in a residential crawl space/basement, apparently due to an oil filter failure. Subsurface investigation demonstrated that the oil migrated primarily along the foundation walls, which resulted in the majority of subsurface contamination being located along and under the foundation. A structural engineering plan was developed to use steel beams to partially support the house and allow incremental excavation beneath the foundations. Chimneys were supported by “pinching” with steel beams. Soil excavation was completed successfully and the foundations were restored.

Petroleum odors, detectable levels of organic vapors, and the hypersensitivity of the homeowner raised issues of indoor air quality. After venting and cleaning were conducted throughout the house, HETI performed a sub-floor vapor screening and collected indoor air samples. The results of these evaluations demonstrated that applicable standards were met and regulatory closure was achieved.

Site Investigation/Remediation, Commercial Property (New England) - HETI performed a site investigation of commercial property formerly occupied by an auto dealership, located in an aquifer protection zone. HETI identified an area of significant soil and ground water contamination, extending to depths of 20 feet below the water table, but demonstrated that the plume was stable and did not threaten water supply receptors. Potential indoor air quality threats were identified. Site closure will require attainment of drinking water quality standards, which will be difficult to attain. HETI designed a remedial approach designed to abate the identified threat to receptors and address ground water quality while maintaining installation and ongoing operation and maintenance (O&M) costs within reasonable ranges for the owner. A soil vapor extraction (SVE) system was installed to remove contaminant mass and abate the indoor air threats. To address dissolved contamination, an air sparging system was operated for about a year before being replaced with oxygen sparging. Dissolved concentrations have been reduced by about 80%, ongoing O&M requirements for the SVE and oxygen sparging systems are minimal, and the actions have satisfied regulatory requirements.

Site Investigation/Remediation, Apartment Complex (New York) - HETI was retained to conduct a remedial investigation of fuel oil contamination under the basement slabs of several buildings. A contractor, assigned by the New York State Department of Environmental Conservation (NYSDEC), had been on the site for more than a year, removing and disposing water/oil mixture beneath the slabs, and was now recommending expensive excavation under the basement. Upon investigation, HETI found the dense clay soil beneath the slabs to be "clean" - with most of the contamination present in a foundation drainage layer immediately beneath the floor. HETI flushed this layer with a surfactant/nutrient bioremedial additive, injecting the solution through multiple borings in the floor. After a month of treatment, NYSDEC declared the spill inactive and issued a No Further Action letter. HETI was successful in obtaining regulatory closure, while saving the client an estimated $50,000.

Manufactured Gas Plant Remediation (Massachusetts) - HETI investigated and remediated a former Manufactured Gas Plant (MGP) site located in a GW-1 (drinking water aquifer) area. The investigation delineated the extent of contamination in shallow and deep overburden aquifers and the bedrock aquifer, and evaluated impacts on surface water and sediment quality. A Phase III evaluation was performed that determined that site closure could be attained with removal of subsurface MGP structures and tar wastes, and excavation and recycling of contamination in the upper 15 feet of the soil column. The excavation required wetlands permitting and extensive excavation dewatering and treatment. HETI completed the remedial activities in accordance with the remedial action.

Ground Water Remediation, Public Works Facility (Rhode Island) - A catastrophic failure of an underground gasoline supply line was discovered when hydrocarbon vapors entered an adjoining residence and evacuation was required. HETI tracked the plume and discovered separate-phase product. Hydrocarbon migration was extremely rapid due to the high soil permeability, and the product plume extended several hundred feet before it was contained. HETI performed ground water pumping tests and designed a multi-well ground water recovery system. The system included air stripping to treat 100 gallons per-minute of ground water, and catalytic oxidation to treat off-gases. The system operated for approximately four years and reduced dissolved concentrations to below drinking water standards in all recovery and monitoring wells. The system has now been deactivated and the site has achieved regulatory closure.

Residential Fuel Oil Remediation (Massachusetts) - HETI was engaged to provide remedial and Licensed Site Professional (LSP) services, after more than 150 gallons of fuel oil were released from a storage tank in the basement of a residence. Nearly all of the oil seeped into the ground before the release was discovered - impacting soil and ground water beneath the basement floor, one of the foundation walls, and the porch. HETI excavated soil beneath the basement floor using hand tools and a vactor truck and installed a recovery well. However, the deepest impacted soil could not be excavated without undermining the foundation and destabilizing the house. Although most of the mass of released oil was recovered with the soil, regulatory cleanup standards had not been achieved for soil or ground water, and sporadic free product remained. Since the house was old, with mortared stone foundations and no footings, HETI concluded that shoring was infeasible. To avoid having to demolish the house, HETI injected remedial additives into the ground, followed by enhanced fluid recovery. Subsequent gauging and sampling verified that free product had been eliminated and all cleanup standards had been met. HETI completed the response actions and achieved regulatory closure.

Service Station (New Hampshire) - At a gasoline service station located 300 feet from an aquifer protection district, HETI performed a site investigation consisting of well installation and a soil gas survey. To remediate separate-phase product, two six-inch diameter gravel-packed recovery wells were installed, and dual pumping systems were installed. Approximately 18 months later, a sudden UST failure resulted in the release of 1,400 gallons of product. The existing system recovered approximately 1,000 gallons of the released product. To enhance recovery of the new spill, a 35-foot long trench was excavated and connected to the existing system. A seven-well soil vapor extraction system was also installed. Of the 1,400 gallons spilled, over 1,350 gallons were recovered by the pre-existing and modified systems.

* This is a brief description of selected Site Remediation projects completed by HETI. For a more complete discussion of our capabilities, please contact us for a copy of our Statement of Qualifications.