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Phase III Remediation:
Hanover Environmental Services, Inc. has provided our clients with responsive, cost effective, and rapid solutions to remove contaminants from the subsurface, eliminate environmental liability, and restore the value of commercial properties and Brownfields sites. We are experienced in utilizing the latest methods of contaminant reduction technology, as well as the proven classic systems that perform reliably for the life of a project.
Some of the remediation systems and activities conducted by Hanover Environmental Services, Inc. include:
Some of these methods are described below:
In Situ Chemical Oxidation (Ozone Sparging)
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In Situ chemical oxidation (ISCO), utilizing direct ozone injection (ozone sparge), is a technique that combines the unit operations of air stripping and oxidative decomposition into a single process. Since ISCO can occur in either the aqueous or gas phase, the ozone sparge method will provide both saturated zone and vadose zone treatment of VOCs and fuel oxygenates present in the subsurface. ISCO treatment is normally concentrated within the source area and subsequently provides a reactive barrier to prohibit the migration of contaminants from the source area. The secondary benefit of the ISCO operations will be enhancing the dissolved oxygen content down-gradient of the sparge points providing oxygen as a biostimulation for the natural biodegradation process. ISCO can also be utilized to form a contaminant migration curtain to treat offsite contaminants witin a large mobile or cutoff plume.
ISCO works by injecting air and ozone directly into the subsurface (sparging). Ozone micro-bubbles (0.5 to 200 microns in size), are generated by a micro-diffuser installed within the sparge point. As the ozone is pumped into the aquifer, dissolved VOCs and fuel oxygenates are transferred from the liquid to gas phase, where they react with ozone in the bubble to decompose the contaminants into simple products (i.e. alcohols, acetate, and formate). Complete oxidation (mineralization) will result in the formation of harmless compounds (water and carbon dioxide). As the ozone is dissolved, any excess not consumed by chemical oxidation reaction will have the effect of increasing the dissolved oxygen content of the groundwater. In areas proximal to the sparge point, ISCO will degrade contaminants and have the effect of sterilizing the naturally occurring bacteria. In areas distal to the sparge point, the enhanced dissolved oxygen levels will stimulate biodegradation of the dissolved hydrocarbon constituents by the naturally occurring bacteria.
In Situ Soil Vapor Extraction (SVE)
In Situ Soil Vapor Extraction (SVE) is a technique for removing contaminants from unsaturated soils. The technique draws soil vapor from the ground with a vacuum pump. The produced vapor brings the contaminants to the surface, where they can be treated and safely discharged. The SVE method is most effective in coarse-grained soils such as sand and gravel. It requires a minimum 5-foot thickness of vadose zone soils. This technique can be used in conjunction with air sparging, groundwater pumping, or the bioremediation options. This technique is able to treat large volumes of soil effectively and with minimal disruption to business operations. It also can remove contamination from near or under fixed structures.
In Situ Bioremediation
Removes biodegradable contaminants from groundwater. Relies upon microorganisms and supplemental oxygen and nutrients to break down petroleum products in the groundwater. In Situ Bioventing with Low Flow Air Sparging
Also known as biosparging. Stimulates the aerobic biodegradation of organic contaminants in groundwater by delivering oxygen to the saturated and unsaturated zones. The oxygen is delivered at a slow rate to encourage biodegradation rather than volatilization. Reduces air emissions and remediates the volatile organic compounds in place. Vacuum Enhanced Pump and Treat
Uses a surface-mounted vacuum pump to remove contaminated soil vapors and groundwater at the same time. Increases the rate of pumping, reducing the remediation time. The pumped water and soil vapors can be treated with various techniques. Pump and Treat
Brings contaminated groundwater above the ground through the use of extraction wells. The water is then treated, normally using one of three processes: granular activated carbon, air stripping, or bioremediation. The pump and treat method is sometimes used in conjunction with soil vapor extraction to enhance the removal of volatile organic compounds from the zone of water table fluctuation. Free Product Removal
Free product is often found in wells on significantly contaminated sites. The removal of free product may be conducted by several methods. A dedicated free product removal device may be installed in the wells to continuously remove free product, for skimmers / separators. Most of these types of systems require very little maintenance, but do require periodic emptying. Hanover Environmental Services, Inc.'s field crews conducte site visits based upon the severity of the free product problem and the capabilities of the device used. Soil Remediation
Hanover Enviornmental Services, Inc. provides a variety of soil remediation services for USTs and other pollution sources.
These include:
- On-Site Remediation: Soil is treated in-situ or ex-situ (with excavating) without leaving the site.
- Aeration, Land Farming: Contamination in the soil is allowed to naturally convert to a vapor state and disperse to the environment or a vapor treatment system.
- Bioremediation: Soil is bioremediated on-site and used as backfill on-site or disposed as clean fill.
- Ex-situ: Soil is excavated and the treatment is conducted above ground using bioremediation.
- Thermal Desorption: Contaminants are thermally desorbed from soil in mobile rotary kiln and the vapors are burned in a flame burner or catalytic oxidizer.
- Vapor Extraction: Contaminants are "vacuumed" from subsurface soils and vapors are treated using thermal oxidation, catalytic oxidation, internal combustion engine, or vapor-phase activated carbon.
- Off-site Remediation: Soil is excavated and removed from the site and remediated at a facility.
Soil remediation services may also include:
- Soil Excavation
- Waste Transportation And Disposal
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Project Experience
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Bulk Petroleum Distribution Facility
Jesse M. Lange Distributing, Inc., 1997 to 2004 |
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A bulk petroleum marketing facility with 30-year operational history changed operations to become a petroleum retailer. The facility upgrade required demolition of above ground storage tanks (ASTs), replacement of the underground storage tank systems (USTs), and installation of fueling bays. During site construction activities, free product was discovered in the UST excavation, and surrounding soils. Non-aqueous phase liquids (NAPL) had been previously documented in monitoring wells and in a nearby utility trench. Following the discovery, Hanover constructed and operated an active NAPL removal system that recovered over 2,500 gallons of free product from the subsurface. Operation of the NAPL recovery system had significant impact on contaminant levels in site groundwater. Detections of free product in monitoring wells discontinued, and contaminant levels in groundwater samples declined by over an order of magnitude. |
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Former Petroleum Retail Facility
Gridley Pit Stop, 1997 to 2004 |
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A release of petroleum products created soil and groundwater contamination that extended from the release point over 2000 feet downgradient. Two dissolved contaminant plumes were present on and off site, with Methyl Tertiary Butyl Ether (MTBE) extending the farthest from the release point. Hanover performed site characterization, engineering properties testing to evaluate potential remedial methods, bench scale testing for remedial actions feasibility, and then implemented full scale remedial system operations. Two separate systems were required as the site was bisected by Highway 99, and the dissolved contaminants were partitioned into two separate plumes. Off site the MTBE plume was remediated with groundwater pump and treat, and onsite the petroleum and MTBE contamination was treated with insitu chemical oxidation and air sparge. Monitoring and reporting of the site was performed on a quarterly basis for corrective actions efficiency and NPDES permit compliance. Treatment systems operations, surface water, and groundwater monitoring was ongoing for the site. To date significant contaminant reduction and hydraulic control of the contaminant plume has been accomplished. |
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Active Petroleum Retail Facility
Esplanade Arco, 1999 |
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A release of petroleum products created a plume of dissolved MTBE that passed under a busy street. Access to the street area was unavailable, and businesses located across the street also impeded the investigation and remedial efforts. The site was subjected to Insitu Chemical Oxidation utilizing ozone sparge technology, and contaminant reduction by orders of magnitude occurred in water samples from monitoring wells. |
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