The Rivervale South to Market project has been designed to provide up to 190,000 dekatherms per day of firm natural gas transportation service from the existing Transco pipeline interconnection with Tennessee Gas Pipeline in River Vale (Bergen County), N.J. to Transco’s Central Manhattan Meter Station in Hudson County, N.J. and the Station 210 pooling point in Mercer County, N.J.
The project has been designed to minimize impacts to landowners and the environment by maximizing the utilization of existing pipeline infrastructure. The project will require a new 0.61 mile pipe segment along the existing Transco pipeline in Bergen County, N.J., modifications to four existing pipeline metering facilities in N.J. and N.Y., and an uprate of 10.35 miles of existing pipe in Bergen County, N.J.
Uprating a pipeline is a process that is used to increase the allowable operating pressure in a pipeline that is not being used to its full design capability. This allows the company to utilize existing infrastructure to transport more natural gas and reduces the need to build additional pipeline facilities.
Pipelines are designed to operate at certain pressures based on the pipe metal’s yield strength, its diameter and its wall thickness. These variables are used to determine the maximum pressure a pipeline can withstand. However, pipelines operate at pressures far below their full material strength. The allowable operating pressure that a pipeline operator cannot exceed is called the maximum allowable operating pressure (MAOP). The MAOP is determined by a variety of factors prescribed in regulations prescribed by the Pipeline Hazardous Materials and Safety Administration (PHMSA), a division of the Department of Transportation. PHMSA requires documentation of the suitable design, construction, operation, and maintenance so a pipeline can operate at its MAOP through any given area.
There are a number of procedures that a company is required to perform before a pipeline can be uprated. These procedures are set out in DOT CFR 49, part 192 and any other applicable code, standard, or specification. Before uprating the pipeline, Transco must first demonstrate that the pipeline can safely withstand the increased operating pressure. The primary test to demonstrate that the pipeline can safely operate at a higher pressure is known as a hydrostatic test. The test is a routine procedure that involves filling the pipe with water at pressures greater than the new desired MAOP for at least eight hours.
For this 10.35-mile section, Transco is proposing to increase the operating pressure by about 20 percent. This proposed increase is less than half of the original maximum calculated pressure for this pipeline section. When this section of pipeline was initially installed, it had sufficient strength in the steel and wall thickness to operate at higher pressures, but due to New Jersey state regulations at the time, it was purposely operated at a lower pressure. That unused pipeline capacity can now be utilized to meet the growing demand for natural gas in the region.
Additionally, pressure regulating and overpressure protection devices must be installed or replaced to handle the higher capacity and pressure on the pipeline section and continue to service existing customers. These too are required to be designed, tested, and placed in service before the pipeline section can operate at its new MAOP.
Along the 10.35 miles of pipeline being uprated, three existing Transco metering stations will also be modified and upgraded to maintain service to customers. All above-ground facilities added or replaced at these stations will be within the existing Transco property lines.
In addition to uprating 10.35 miles of existing lateral, there will be some debottlenecking required at the intersection where the volumes from this lateral flow into the mainline. This will be done with a 0.61 mile loop along the existing mainline pipeline within an unpopulated, maintained wetland owned by Williams. Looping a line is where a pipeline is laid parallel and tied in to an existing pipeline to increase overall flowing capacity. This 0.61 mile loop section will be in the meadowlands area on property currently owned by Williams and adjacent to a Transco station and mitigation bank that is maintained by Williams. Williams is sensitive to the ecosystem of the area and will control disturbances and return the wetlands to their former condition.
Central Manhattan Meter Station
The existing Transco Central Manhattan meter station will be upgraded to handle the additional capacity. This will include upsizing the piping in and out of the station as well as replacing the overpressure protection valves. This meter station is actually not in central Manhattan, but serves it from the New Jersey side, and is in a commercial area.