Case Studies

Atlanta Gas Light Co: In Situ Stabilization of MGP Impacted Soils

Project Summary

In Situ Stabilization of Former Manufactured Gas Plant in Augusta, GA

A former Manufacturer Gas Plant (MGP) site was scheduled for cleanup under a State sponsored environmental restoration program. The site had a history of MGP activities dating back to the 1840s that had impacted the subsurface of a large area which was now occupied by a historic church, four lane city street, historic water canal, small businesses and residential areas. Under the State program, the portions of the subsurface below the groundwater table were designated for treatment with Insitu Stabilization (ISS).

Geo-Solutions served as the primary sub-consultant for this and a similar nearby project, and performed a number of critical tasks including:

1) on site supervision of the final exploratory boring program;
2) formulation and testing of design mixtures of cement grout to treat the MGP impacted soils;
3) expert technical services to explain parts of the construction process and design mix performance to State regulators;
4) on site supervision of a pilot ISS project;
5) providing specialty grouting equipment and equipment supervisor for the pilot project;
6) devising the quality control program for construction;
7) specifications for the ISS construction;
8) assistance in selecting the construction contractor; and
9) oversight of the startup of full scale construction.

In Situ Stabilization Process of Former MGP in Augusta, GA

Geo-Solution's involvement in the project led to a number of improvements in the project design and significantly reduced the cost of construction. The final boring program identified three distinctive cases (clay, sand, and peat) that required three different design mixtures to achieve successful performance. The mixtures of grout materials formulated by Geo-Solutions provided successful treatment of the MGP waste at a savings of over $10,000,000 in materials compared to earlier design mix studies. Final prices for the soil mixing were contracted at about $50/cy of treated soil.

The pilot project for this site is still one of the largest and most comprehensive evaluations ever of the ISS method for the treatment of contaminated soils. Twenty four test columns were construction up to 30 ft deep with diameters of 6 and 8 ft. The three cases: sand, clay, and peat were all successfully treated. A special additive was used in the clay case to help the contractor to overcome difficult drilling and mixing conditions.

Performance criteria for the ISS treatment relied primarily on the reduction of permeability, increase in strength, and reduction of leachate generation as measured by the SPLP (synthetic precipitant leaching procedure) test. Geo-Solutions provided a key role in selecting and specifying the performance criteria.

The successful remediation of this site was eventually completed using the methods and design mix formulations devised by Geo-Solutions.

ISS Dimensions

Geo-Solutions Can Help

To download, read, and learn more about the various soil mixing sample specs and technical papers we offer online here at Geo-Solutions.com, click on the links below or to your left:

• Soil Mixing Sample Spec– Geo-Solutions provides a soil mixing sample spec which can be modified for real world use on your project. Download sample specification for Soil Mixing .

• Soil Mixing Technical Papers – Browse our library of Soil Mixing Technical Papers.

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