O&R begins final phase of Nyack coal tar clean up


OR Nyack MGP 3_14_14 I0434O&R begins ramping up this week on the final phase of its project to clean up the coal tar residue at the former manufactured gas plant (MGP) site at 55 Gedney Street in the village of Nyack.

The plant, which extracted gas for lighting and cooking from coal and oil, was owned by a predecessor company of O&R. The predecessor company closed its doors over 50 years ago, and its building has long-since been demolished. But, residue from the process remains underground along the shoreline and in the sediments adjacent to the four-acre, vacant, riverside lot owned by Athene Annuity and Life Assurance Company (formerly Presidential Life Insurance Co.).

O&R already has successfully cleaned up the upland part of that lot. In 2005 through 2006, O&R excavated and trucked out more than 20,000 tons of impacted soil and replaced it with clean fill on the western part of this site. In 2006 and 2007, O&R solidified the coal tar residue located in soils along the river on the eastern part of the site and entombed these impacts in an underground cement monolith — a process known as in situ solidification. When the work was complete, the site was covered with clean topsoil, 2-feet-deep, and restored to a park-like setting.

The in situ solidification process now will be repeated to address impacts remaining in soils along the shoreline. A sheet-pile cofferdam will be installed along the shoreline to manage river water while the solidification process takes place. Equipment for the solidification process includes large drill rigs with specialized augers and a batch plant to mix the cement slurry.

The top two feet of soil will be excavated and soils below will be mixed with the cement grout material to the depth of the coal tar residue and entombed.

Once the solidification process is completed, river sediments containing coal tar impacts will be dredged up and trucked to an approved off-site treatment/disposal facility. Dredge work will extend approximately 150 feet into the river. Before the sediments are trucked off site, they will be de-watered and amended to dry them out for transport.

The management of the sediments will take place under a large, tent-like, fabric structure equipped with an air-handling and carbon-filter air treatment system. These air-handling devices will be shrouded with sound-dampening equipment. The temporary structure will be approximately 68 feet wide, 82 feet long and 29 feet high.

Real-time air monitoring will be conducted on a 24-hour, seven-day per week basis at key perimeter points to ensure that air monitoring criteria are met so that odor mitigation steps can be taken if needed. All results from those monitoring stations will be shared with the New York State Department of Health (NYSDOH), which also is monitoring the project along with the New York State Department of Environmental Conservation (NYSDEC).

The excavated soil and sediments will be loaded into tractor-trailers, whose tires will be cleaned of any ground soil before leaving the site. The trucks will proceed up Main Street, taking a right onto Polhemus Street, which leads directly to an entrance ramp to the NYS Thruway northbound. This is the same route that was successfully used during the previous work at the site.

The excavated soil and sediments will be trucked for treatment and disposal to an approved, licensed facility in Keasbey, N.J.

The site will be restored to its current park-like setting with a stone-slope covering to protect the shoreline. Currently, O&R estimates that approximately 19,500 tons of soil and sediment will be trucked out for disposal and about 6,850 cubic yards of soil will be solidified to entomb remaining coal tar residue.

The project is due to be completed by December 2014. This phase of the project is expected to cost $9.8 million. To date, O&R has spent $14.9 million remediating the Nyack MGP site.

The construction work will be performed Monday through Friday 7 a.m. to 5 p.m. No noise generating activities will be conducted before 8 a.m. Sound levels will be consistent with a typical construction project site. Gedney Street will remain open during the project and truck traffic in and out of the site will be controlled with flaggers. Security will be provided on the site during evening hours and weekends and holidays.

More than 1500 manufactured gas plants operated throughout the U.S. from the mid-1800s through the mid-1900s to provide gas for lighting and heating. The plants used a variety of processes to make gas by heating coal and/or oil. The by-product from this process was known as coal tar. Very often, these coal tars were left behind in subsurface structures and soils when the plants were closed.

O&R and the NYSDEC signed an agreement in 1996 in which the utility undertook an examination of its seven former manufactured gas plant sites in Orange and Rockland counties to determine whether any coal tar or other residue from the obsolete gas manufacturing process remains on the sites.

Historical records indicate that a manufactured gas plant operated on this site from 1852 until 1965. It is believed that gas was made from coal and oil from 1852 until 1889, and from 1890 until 1938, the plant used both coal and oil as feedstock for the carbureted water gas process. From 1938 until 1965, the site was used as an oil gas facility only during times of peak demand, a practice known as “peak shaving.”

Orange and Rockland Utilities, Inc. (O&R), a wholly owned subsidiary of Consolidated Edison, Inc., one of the nation’s largest investor-owned energy companies, is a regulated utility. It provides electric service to approximately 300,000 customers in southeastern New York State (where its franchise name is Orange & Rockland), northern New Jersey (where it’s Rockland Electric Company) and northeastern Pennsylvania (where it’s Pike County Light & Power Company) and natural gas service to approximately 130,000 customers in New York and Pennsylvania.

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