A facility used to manufacture coal gas, carburetted water gas (CWG), and oil gas is today generally referred to as a manufactured gas plant (MGP).

Depending on the processes used for its creation, coal gas is a mixture of the calorific gases: hydrogen, carbon monoxide, methane and volatile hydrocarbons, with small amounts of noncalorific gases - carbon dioxide and nitrogen - as impurities. Coal gas plants, especially those that operated in the past, are commonly referred to, by environmental professionals and within the utility industry, as "MGPs."

Old MGPs pose various environmental risks and remediation challenges. These include.....

Former MGP Site (Isotec Case Study 21)

• Site Location: Long Beach, California
• Contamination: PAHs (2,484 mg/kg) including Benzo(a)Pyrene (100 mg/kg, 340 µg/l ), and TPH (27,800 mg/kg, 912,000 µg/l ).
• Geology: Fill material overlying poorly sorted medium to fine grain sand; water table at approximately 10 ft bgs.
• Area Treated: Approximately 3,000 Sq. ft area at 7-12.5 ft bgs vertical depth interval.
• Effectiveness: In soil, TPH reduced by 58%, BaP equivalent by 89%; TPH & PAHs were ND in groundwater.

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• Site Location: Long Island, NY
• Contamination: VOCs, primarily BTEX & Naphthalene (BTEX 501,000 ppm in soil, 300 ppm in GW).
• Geology: Fine to course grain sand with gravels underlain by 2-6 ft thick peat layer.
• Area Treated: Approximately 29,200 sq. ft at an interval of 5-12 ft bgs.
• Effectiveness: Site-wide BTEX & Naphthalene in soil were reduced from 644,498 ppm to 12 ppm. This site is currently undergoing a long term monitoring program under NYSDEC review.

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• Site Location: Nyack, NY
• Contamination: Bedrock contaminated with non-aqueous phase liquid (NAPL) and MGP-related compounds. Primary contaminants of concern (COCs) include volatile organic compounds (VOCs), Poly-nuclear aromatic hydrocarbons (PAH's) and total petroleum hydrocarbons (TPH). Levels of COCs reached 6 mg/l for VOCs and 1,200 mg/l for PAHs in the dissolved phase and 8,500 mg/l for VOCs, 36,000 for PAHs and 900,000 mg/l for TPH in NAPL.
• Geology: Fractured bedrock
• Area Treated: ~36,000 cubic yards consisting of 20 vertical feet of an impacted bedrock zone.
• Effectiveness: Successfully treated a large portion of the free phase NAPL present in the bedrock. The entire project was completed ahead of the schedule and under the budget (the total cost of the treatment program was ~ $300,000 . The project was given an "Award of Merit" by the New York Construction Journal in 2007.

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• Site Location: Macon, Georgia
• Contamination: Naphthalene, Benzene, Toluene, Ethylbenzene, Total Xylenes (BTEX), PAHs and by-product-like material (BPLM).
• Geology: Fill material from 0.2-13 feet bgs underlain by alluvial deposits, which is underlain by saprolite. GW is encountered at varying depths throughout the site ranging from 6-25 feet bgs; flow is in the east-southeast direction.
• Area Treated: Two areas; larger off-site area approximately 285 ft x 160 ft and the smaller on-site area 50 ft x 50 ft.
• Effectiveness: Based on the operational criteria set forth for the site, majority of wells installed during Phase I have met their remedial requirements and no further injections into those areas are proposed.

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