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Updated: Blasting Won’t Affect Transco Compressor Station

A rendering of the proposed Transco natural gas compressor station 206. Source: Transco.


Update: “Blowdowns” at the proposed Transco natural gas compressor station 206 could occur four to five times a week, for four to six weeks, while the compressor station is being tested, a company spokesman said.

A blowdown is a forced release of gas into the air.

Transco spokesman Christopher Stockton said that the number of blowdown events vary, based on need.

“The blowdowns during commissioning are a result of all of the different tests that have to be run on the different pieces of equipment and piping,” Stockton said in an email. “Construction describes the testing as ’cause and effect’ testing, which is necessary to ensure that all of the equipment is functioning as designed.”

“Following construction, unit blowdowns may happen several times per year and are associated with planned maintenance of a compressor unit, and/or associated piping,” he said in the email. “In both cases, these blowdowns are planned and controlled, with gas flowing through a blowdown stack which consists of a deodorizer and a blowdown silencer, minimizing any odor and sound associated with the event.”

Original Story: A natural gas compressor station proposed to be built in the township could be constructed so that it would not be affected by blasting from a nearby quarry.

That’s the assertion included in a March 27 application for the station submitted by the Transcontinental Gas Pipeline Co. to the Federal Energy Regulatory Commission.

The company, known as Transco, an affiliate of the Williams Companies, also included in its application a report saying that noise from the station would not exceed federal standards.

Transco’s submission of the application for a certificate of public convenience and necessity is the latest step in the process to get permission to build a 32,000-horsepower natural gas-powered station on a 52-acre parcel near the intersection of Routes 27 and 518. The controversial application has run into opposition from residents and officials in Franklin and South Brunswick.

Plans call for the construction of five buildings – a compressor building, a power controller/air compressor building, an office/warehouse building, a small drum-storage building and a telecommunications building – a communications tower, above-ground storage tanks, a standby generator and a medium voltage transformer, according to the application.

The compressor station is part of Transco’s $1 billion Northeast Supply Enhancement Project. In addition to the Franklin compressor station, the full project consists of consist of approximately 10 miles of 42-inch pipeline looping facilities in Pennsylvania, three miles of onshore 26-inch looping facilities in New Jersey, 23 miles of offshore 26-inch looping facilities, the addition of 21,902 horsepower at an existing compressor station in Pennsylvania, and related facilities, according to a Transco press release.

The company noted in its application that it is “currently evaluating the feasibility of using municipal water as a water supply for Compressor Station 206. Additional information regarding the water source to be used at Compressor Station 206 will be provided in a supplemental filing in the 2nd quarter of 2017.”

Township officials have expressed reservations about the amount of water available in the area should there be an emergency.

Transco anticipates that the station should be running by December 2019.

Compressor stations raise the gas pressure in pipelines so the gas can make it to its final destination. The enhancement is necessary, Williams’ representatives have said, because one of its natural gas customers is projecting an increase in need in several New York City boroughs.

The proposed site is about 1,500 feet from the Trap Rock Quarry, the activities of which include regular blasting. Concern has been expressed by opponents to the station over the affect that blasting would have the gas compressors.

But a report prepared by Geosyntec Consultants of Houston, Texas, says that the compressors and their affiliated buildings could be constructed in such as way as to mitigate any vibrational effects from the blasting.

The company conducted blast vibration monitoring on Nov. 10 and Dec. 2, 2016, according to its report. Three sensors were used for the tests, and the company also integrated information on previous blasting activity provided to it by Trap Rock.

Trap Rock is selling the parcel to Transco for the project.

The test results showed that with proper construction, the buildings could be constructed with minimal affect from the vibrations caused by the blasting, according to the report.

Among the report’s recommendations are the following:

  • Each piece of equipment should be placed on an independent mat foundation in the general layout provided by Williams.
  • Geotechnical capacity analyses should be conducted by the Engineer of Record to verify that appropriate factors of safety are met for all load combinations (e.g., dead load, live load, earthquake load, wind load, etc.)
  • The top 4 feet of vegetative soil should be excavated prior to construction of the mat foundations and should not be used as structural fill. The foundation depth of 4 feet below ground surface is to ensure that the mats lie below the soil frost depth.
  • …(t)he likelihood of blast-induced ground vibration exceeding the maximum measured values is low, however, Williams should confirm with Trap Rock that the past record of blast intensity reflects future events.

Transco’s contractor for the acoustical analysis, Houston-based Hoover & Keith, found that “if the anticipated and/or recommended noise control measures are implemented successfully, the sound contribution of the proposed Station should be equal to or lower than 55 dBA (Ldn) at the nearby (noise sensitive areas, or NSAs), which is the FERC sound level requirement for this type of facility.”

The report also concluded that “the acoustical analyses indicate that the noise of construction activities and noise resulting from a unit blowdown event at the Station should have limited noise impact on the surrounding environment. In addition, since Station noise sources that could cause perceptible vibration (e.g., turbine exhaust noise) will be adequately mitigated, there should not be any perceptible increase in vibration at any NSA during Station operation.”

A “blowdown” is the release of gas into the air, which occurs during normal operations or in an emergency. Opponents of the station say the blowdowns will add to air pollution and will be noisy for the residents who live nearby.

Among the recommendations made for noise abatement are:

  • As a minimum, walls/roof should be constructed with an exterior skin of 22–gauge metal, and building interior surfaces should be covered with 6–inch thick “high-density” mineral wool … covered with a perforated liner
  • No windows or louvers should be installed in the building walls although a minimum number of skylights could be installed in the building roof although not anticipated;
  • Each large access door system (i.e., “roll-up door”) should consist of an insulated-type door; personnel entry doors should be a STC-36 sound rating , even if glazing is employed and should be self-closing and should seal well when closed;
  • It is anticipated that the building air ventilation system will be designed with air supply fans mounted in the building walls along with roof-mounted air exhaust vents or a roof ridge vent to exhaust the air (i.e., wall louvers should not be employed). Assuming this type of air ventilation system, the sound level for each wall air-supply fan should not exceed 50 dBA at 50 feet , which will require that each fan employ an exterior dissipative-type silencer … and an acoustically lined weatherhood.
  • The turbine exhaust system for each turbine-driven compressor unit should include a silencer system
  • Acoustical pipe insulation should be employed for aboveground suction gas piping, discharge gas piping and any recycle (surge control) gas piping. Acoustical pipe insulation should consist of a minimum 3-inch thick fiberglass or mineral wool … that is covered with a mass-filled vinyl jacket. All exposed pipe supports for the insulated gas piping should be covered with acoustical insulation or a type of acoustical blanket material.
  • Outdoor valves should be covered with a type of “tight-fitting” acoustical blanket material. Filter–separator(s) and associated aboveground gas piping should not have to be covered with any type of acoustical material unless deemed necessary after operation of the Station.
  • Aboveground inlet pipe risers and inlet header for the Station gas cooler should be covered with acoustical pipe insulation although the outlet pipe risers should not have to be covered with acoustical pipe insulation.
  • The turbine air intake system for each compressor unit should be designed with at least one (1) in-duct silencer
  • The unit blowdown silencer for each Station compressor unit should attenuate the unsilenced blowdown noise to a noise level equal to or less than 60 dBA at 300 feet from the outlet of the silencer, which includes the noise radiated from the shell of the blowdown silencer during the blowdown event.

Although regularly-scheduled “blowdowns” should only occur every 1-3 months, the initial commissioning and testing of the compressor station could involve 2-4 “blowdowns” a day, according to the report. It was not immediately known how long the testing period usually lasts.

 

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