South Lakes Subdivision Gas Distribution System

Project: South Lakes Subdivision Gas Distribution System



South Lakes Subdivision Gas Distribution System

In May of 2022 FTC began the installation of gas lines to feed the new townhome and single-family residences in the new South Lakes Subdivision in Upper Marlboro. This project was somewhat out of the ordinary as there was no gas distribution mains in the area capable of supplying a subdivision of this size (ultimately 563 townhomes, 344 single family homes, 128 two-family attached homes, a clubhouse as well as future retail). New streets were in, and townhouse construction had already begun. FTC needed to meet a fast-tracked timeline. To meet the settlement dates, we had to mobilize quickly to get gas to these new homeowners. A project that would normally take seven or eight months needed to be completed in four months.

This gas distribution system was comprised of four phases: Onsite Main, Approach Main, Regulator Station, and Transmission Main.

Natural gas is dispersed from a transmission main at a pressure of 300lbs+/-. Regulator Stations are needed to reduce the operating pressure to 60lbs or less. The first pilot on the upstream regulator will operate as a standby monitor to sense downstream pressure to confirm that the station outlet pressure does not exceed acceptable levels. The second pilot will regulate the pressure between the two regulators to a typical intermediate point of 125psig. The second regulator has 1 pilot controlling the normal station outlet pressure (55lbs). The Approach Main takes gas from the regulator station and delivers it to the onsite main to distribute into each residence.

Transmission Main: Coated steel pipe operating at +/- 300 lbs.
Regulator Station: Made of coated steel pipe, this installation is used for automatically reducing, regulating, or limiting downstream pressure. Reduces pressure of transmission main through double hump regulator to disperse to distribution pressure.
Approach Main: 8” plastic gas pipe connects regulator station to onsite main.
Onsite Main: 2”, 6”, and 8” plastic gas distribution main feeds individual services later installed for each residence.

Delayed Permits, New Routes, & Expedited Timelines

Special permits were required from the State Highway Administration (SHA) due to a necessary lane closure on Old Central Ave and approval of project plan changes. Unfortunately for our team, these permits were delayed by approximately two months. This impacted not only our schedule but the order in which we installed the gas lines for this project.

Prior to the project start, vehicles traveling East on MD 214 could access Old Central Ave via an on-ramp. The ramp was to be decommissioned because its location would become the site of the new underground regulator station. Although the ramp was permanently closed, vehicular traffic had to remain open. To accommodate a new traffic pattern, SHA installed a traffic signal to create a righthand turn onto Old Central Ave from MD 214.

The original plans had the Approach Main going behind the utility pole line on the north side of Old Central Ave which placed the main on private property. The second revision of the plan had the main being installed 2’ in front of the pole line, this version conflicted with WGL standards that indicate a minimal distance of 5’ from a utility pole. The third and final revision of the plans placed the main in the roadway, away from the utility pole line.

During a standard infrastructure installation such as this, FTC would have started with the Transmission Main and worked towards the Onsite Main “gassing up” as we connected each section. Instead, due to the delayed permit, we had to start by installing the Onsite Main then work backwards connecting the Approach Main, Regulator Station, and Transmission Main.

FTC hired B&J Flaggers to manage the traffic flow during FTC operational hours. This was very important as we enforced a lane closure to install the 961’ of 8” plastic gas pipe that travels under the shoulder of Old Central Ave. Additionally, we crossed under Old Central Avenue to connect the Approach Main to the Regulator Station. Heavy equipment, trucks, and crew members were frequently crossing the street to access the different construction and storage areas.

FTC was granted special workdays by SHA to expedite the project. We were given the ability to work extended hours and additional workdays to include Holiday weekends such as Labor Day. Normal working hours on a state road are between 9am and 3:30pm. FTC was allowed to begin work at 7am and work until 7pm. This was a huge benefit given to our crews.

The timeline, size and complexity of this project required FTC to double up on resources. Throughout the four months, we had two highly experienced crews working long hours.

Specialized Training

Natural gas is highly sensitive and combustible. To work on the natural gas system, specifically WGL for this project, crew members must obtain specialized training and obtain required Operator Qualifications (OQ’s).

South Lakes Subdivision Gas Distribution System consisted of two types of gas pipes – Polyethylene Plastic Pipe and Coated Steel Pipe. A standard pipe length is 40’. So, how does an underground utility contractor connect the pipeline to create a fully functional natural gas system? As one can imagine, it depends on which of the two types is being installed – steel vs plastic.

Steel pipe
The regulator station and transmission main installation was comprised of coated steel pipe. Our scope of work included roughly 80’ of 6” steel pipe, 180’ of 4” steel pipe, 21’ of 1” steel pipe, and 320’ of ¾” steel pipe for the Regulator Station plus 118’ of 6” wrapped steel and 4’ of 4” wrapped steel for the Transmission Main.

Between the regulator station and transmission main there were over 200 welds, 93 alone inside an 8’x130’ pit for the regulator station. All welds had to be x-rayed, wrapped and “jeeped” to ensure a proper and safe seal was created. (Full description of process and definitions within Specialized Training document submitted under safety section.)

Polyethylene Plastic Pipe
We connected and installed over 2,900’ of 8” Polyethylene plastic gas pipe, 516’ of 6” plastic gas pipe, 8653’ of 2” plastic gas pipe for the Onsite Main phase as well as 961’ of 8” plastic gas pipe for the Approach Main phase.

FTC has qualified and experienced Pipefitters that perform a specialized process called Butt Fusion using a McElroy 28 Hydraulic Butt Fusion Machine. This process consists of melting the ends of the plastic pipe then using pressure to join/fuse them together (detailed Butt Fusion Process is described under safety section of submission, please read).

Lowering gas pipe that has been fused together to establish lengths needed for a project of this size is no small feat. Throughout the project, we used several large excavators and other equipment to hoist and lower the lines into the open trench. This equipment was also necessary to place the steel pipe properly due to its size and weight.

Additional Quarrels
The existing transmission line that was to be tapped to connect the new system was at the top of an overgrown hill. Crews had to clear the hillside of all overburdens and create a safe and accessible path to install the new infrastructure. After the site was cleared, we established the proper and safe trench depth utilizing a 3:1 slope, shoring box, and shielding. During the final stages of this project we reseeded, laid straw, and placed erosion control mats to rejuvenate the landscape. We also paved approximately 800’ of asphalt to resurface our trench line in the roadway on Old Central Ave.

Throughout the project duration, we consistently communicated and coordinated with SHA and the developer, Chesapeake Realty Partners. We all used the same route to access the different construction areas for installations, storage, hauling, deliveries, etc. Additionally, there were other companies installing wiring and ducts for streetlights, curbs, and gutters, building homes onsite and making deliveries.

Our team of highly skilled workers completed this extremely intricate natural gas distribution system within four months without injury or near misses – normally a 7-to-8-month process cut nearly in half! All work was overseen by WGL and Public Service Commission. FTC was given high praise for the completion of this project. We are proud of the work we’ve done and give all the credit to our crews for another job well done.

About us

A leading underground utility business based in Odenton, MD, Ferguson Trenching Company performs all facets of underground utility and site work construction for private developers, counties, municipalities and state and government agencies.