Description of Work:
Geo-Solutions was the general contractor for the closure of an old refinery landfill located adjacent to the Genesee River in Wellsville, New York. Project work included excavation of satellite waste, stabilization of waste in the landfill, construction of a soil-bentonite slurry wall around the site and construction of a RCRA cap covering the entire site.
- Satellite waste along an old railroad bed was excavated and transported to the landfill as part of the closure. Soft spots in the landfill were stabilized by mixing Portland cement with existing materials. Slurry wall construction consisted of the following:
- Mobilization of excavating equipment and a specialized bentonite slurry mixing plant;
- Construction of 2,800 LF of work pad;
- Excavating slurry trench to depths of 40 feet (3 feet into underlying clay layer);
- Mixing and placement of 85,000 SF of clay backfill wall;
- Construction of a traffic cap over the entire wall; and
- Construction of a synthetic underliner which keyed into the slurry wall and the RCRA cap.
Technical requirements for the slurry wall specified a permeability of less than 1×10-7 cm/sec.
RCRA cap construction consisted of the following:
- Clearing and grubbing the 12-acre site;
- Preparing subgrade and constructing a gas vent pipe system;
- Constructing a 550,000 SF cap consisting of geotextile, 12 inches of gas vent stone, gundseal geocomposite liner, 60-mil VLDPE liner, geonet, 18 inches of cover soil and 6 inches of topsoil;
- Riprap drainage swales were constructed in the valleys of this low profile cap; and
- Vegetative cover completed the cap.
A full-time health and safety officer (HSO) was onsite providing technical and administrative support with respect to health and safety and industrial hygiene. This consisted of site safety audits, Health and Safety Program implementation, and real-time air monitoring. The contaminants of concern on this project consisted of aromatic hydrocarbons (benzene, ethylbenzene, toluene, and xylene), polynuclear aromatic hydrocarbons (PAHs) (naphthalene), and metals (lead and arsenic).
Real-time air monitoring consisted of a utilizing a photoionization detector for volatile organics, total dust monitoring utilizing a PDM3, combustible gas indicator, oxygen monitor, radiaiton meter, and colorimetric evaluation. Personnel time-weighted average (TWA) air sampling was performed for aromatic hydrocarbons and the two metals. Meteorological data was tracked daily via the local weather station.
