Diverting the Flow

The topic of infrastructure construction and repair has been thrust into the national spotlight. Of particular interest are the proposed upgrades and installations for wastewater and stormwater management. The first step of any trenchless rehabilitation project of this kind involves diverting the flow. As more and more contractors opt for trenchless rehabilitation, coordinated efforts are increasing to identify and install pumping solutions that are reliable and environmentally responsible.

One Project, Many Solutions in Clark County, Nev.

When the Clark County Water Reclamation District in southern Nevada learned that the existing infrastructure of the east valley portion of Clark County (near the water reclamation facility) was more compromised than originally anticipated, it scheduled a two-phase project that resulted in 44 miles of rehabilitated pipeline. As a result, what was initially thought to be a relatively simple, $3 million project expanded to a massive, $87 million emergency repair/replacement design-build project steered by Las Vegas Paving Corp.

“We rehabilitated or replaced all of the pipelines within an area of four square miles,” said Bill Wellman, division manager for Las Vegas Paving. “But we couldn’t start on the replacement portion of the project until all flows to the reclamation plant were bypassed.”

The sewer bypass phase involved 15 months of uninterrupted bypass using portable bypass pumps to temporarily re-route 127 mgd of wastewater through an intricate network of 220,000 lf of high-density polyethylene (HDPE) pipe. The goal of the bypass phase was to empty the pipes that normally discharge into the District’s central plant at Flamingo and Stephanie so that crews could assess the condition of the underground lines and begin rehabilitation work that could involve relining or replacing existing lines. The bypass pumps needed to reliably re-route the wastewater so that the District could continue normal operations while the rehabilitation and/or replacement proceeded.

Because of the quantity of pumps and when they were required for the project, Wellman made the decision to purchase pumps — instead of renting them — from Godwin Pumps. Godwin manufactured 53 of its diesel-driven, 12-in. and 18-in. Critically Silenced, automatic self-priming Dri-Prime pumps in an unprecedented period of just 90 days.

Throughout the 15-month pumping phase, there were 17 separate pumping locations that were monitored 24 hours per day and rated to handle an average daily flow of 127 mgd and a peak daily flow of 265 mgd of wastewater, plus redundancy.

Phase II of this project involved the cured-in-place pipe (CIPP) rehabilitation of the existing lines, including 6,576 lf of 30-in. and smaller pipe, and 28,992 lf of 36- to 72-in. pipe for a total of 35,748 lf of CIPP rehabilitation. In addition, three new 84-in. lines were added with the intention of increasing capacity in an effort to comfortably sustain future growth.

“Adding new lines while this project was already under way is the most cost-effective and logical way to address future growth. The District did not want to inconvenience residents or the commuting public twice. Since we already needed to get in and rehabilitate or replace existing pipe, we added new lines that will help the District support new construction well into the future,” said Wellman.

Stewardship in Cape Fear, N.C.

When the Cape Fear Public Utility Authority (CFPUA) in Wilmington, N.C., issued an emergency bid to reline 720 lf of 48-in. iron pipe with CIPP liner, Indiana-based Reynolds Inliner LLC answered the call. The setup location for this project fell within the U.S. Army Corps of Engineers’ wetlands and included strict specifications for not disturbing the root system of any vegetation during system setup and tear-down. This made the project site accessible only at the top end and bottom end. In addition, the project passed through a navigable waterway (Burnt Mill Creek), and included navigation over an existing railroad easement and under an existing railroad bridge.

The bypass pumping work on this emergency project was awarded to Godwin Pumps. Godwin provided a 20 mgd bypass with 100 percent redundancy (40 mgd bypass total) through eight of its Critically Silenced Dri-Prime model CD225M 8-in. by 8-in. pumps and two Critically Silenced Dri-Prime model CD100M 4-in. pumps. The pumps tied into a manifold, to an 8-in. HDPE line crossing the Creek, and then into the existing 24-in. HDPE line via a tapping saddle.

“Bypass pumping for this job began in early November 2008 and the initial relining was completed by Thanksgiving week,” said Godwin Wilmington, N.C., branch manager Jarrod Williamson. “During construction, additional problems with the existing infrastructure were uncovered. This required an extension to the pumping contract, and control of the contract was then transferred to the Authority.”

“We had to consider many factors in this job setup, including noise reduction — since it is in proximity to residential areas) environmental sensitivity — since it rests in designated wetlands and setup — as the site was only really accessible from the ends,” said Godwin Southeast regional manager Bud Nichols. “This was the largest bypass of its kind for our Wilmington office, but not for Godwin Pumps as a whole. We were able to rely on the experience and engineering expertise we have to provide a solution that has worked as promised for the Cape Fear Public Utility Authority.”

Safe Practices in Protected Areas in Baltimore County, Md.

As the primary contractor for Halethorpe in Baltimore County, Md., Spiniello Companies, Fairfield, N.J., is currently coordinating the installation of roughly 7,040 lf of 42-in. CIPP, roughly 11,635 lf of 48-in. CIPP, roughly 4,605 lf of 54-in. CIPP and roughly 14,410 lf of 66-in. CIPP as part of the Patapsco Interceptor and Relief Sewer Rehabilitation consent decree project. The project calls for the simultaneous diversion and bypass of 80 mgd of sewage with average flows of 20 to 50 mgd at a total dynamic head (TDH) of 78 ft. The Patapsco Interceptor project rests in the flood plain of the Patapsco River and in the protected eagle nesting areas within Patapsco Valley State Park.

“This project had very clear specifications regarding onsite capability and standby availability of pumping equipment,” said Nichols. “We have had the opportunity to work with Spiniello Companies in the past, and we believe that the proactive and responsible measures they took in planning this project will help eliminate the possibility of accidental overflows into the national park, and/or the inability to handle flow in the low-lying flood plain.”

Spiniello Companies division manager Gerhard Rodenberger, project manager Julio Arzola, Godwin sales engineer Chuck Inman and Nichols selected Godwin Dri-Prime CD400M 18-in. by 18-in. skid-mounted, diesel-driven pumps, capable of flows up to 9,000 gpm and TDH of 147 ft. The pumps feature Tier III Caterpillar C-9 engines, which comply with current U.S. government emissions standards and are equipped with PrimeGuard Controllers that help to regulate the pumps for maximum efficiency. The project will use as many as eight CD400M pumps in an effort to maintain 50 percent redundancy throughout the scope of the project at anticipated flows from 20 to 50 mgd.

Reducing Impact

When it is feasible, utilities prefer to perform trenchless work — particularly in environmentally sensitive and/or high traffic areas. In every instance where such work is required, reliable pumping plays an equally critical role in successful project implementation.

Stephanie Morgan is corporate communications manager for Godwin Pumps, which is headquartered in Bridgeport, N.J.