Pleasure Bay Interceptor honor, lessons for trenchless

A New Jersey sewer interceptor upgrade earned Project of the Year Honorable Mention after a major mid-drive setback and a successful rescue. The Two Rivers Water Reclamation Authority (TRWRA) started with an earth pressure balance TBM under the Shrewsbury River, lost it to flowing sand, then finished the crossing using a slurry microtunneling plan.

The account and project facts come from trenchlesstechnology.com. For trenchless contractors and owners, the sequence shows how to plan for ground surprises, protect shafts and crews, and keep a river crossing alive when equipment is trapped.

Scope, assets and the original plan

TRWRA serves about 90,000 customers on the Jersey Shore. In 2021, the agency found deterioration in the more than 50-year-old Pleasure Bay Interceptor and the Main Pump Station, which had also been damaged during Superstorm Sandy. The plan called for a new 54-in. Pleasure Bay Interceptor and a new pump station, tying in the existing 30-in. Monmouth Beach Interceptor, and a force main to the treatment plant.

Major structures included a 50-MGD station in an 80-ft-diameter, 120-ft-deep shaft. The design also added a 100-ft-deep drop structure in a 30-ft-diameter, 110-ft-deep shaft. The river crossing required 3,300 lf of 54-in. interceptor installed inside a 9-ft-diameter tunnel.

Baseline geotechnical expectations at tunnel depth were nearly impermeable clay. Based on that, the team prepared to launch an earth pressure balance tunnel boring machine from the Monmouth Beach shaft and advance 3,300 lf beneath the Shrewsbury River to the Oceanport drop shaft.

What went wrong under the river

The EPBM advanced in open mode. At 2,100 ft into the drive it hit flowing sand. The inflow buried the machine. Crews evacuated and shut the emergency flood doors. The contractor and owner wrote off the EPBM and the team faced a full redesign of the interceptor plan under the river.

Ground mischaracterization is not rare under waterways, but the sequence here is specific and instructive. An EPBM set up for open-mode progress in clay can be compromised by running sands. Once the face becomes unstable, crews and shafts need quick isolation. Emergency doors did their job, but the machine was not recoverable in place.

The rescue: microtunneling through a failed tunnel

Kilduff Underground Engineering Inc. (KUE), Northeast Remsco Construction, and owner’s engineer Hazen & Sawyer studied the options and chose a direct approach. They selected a slurry microtunnel boring machine to drive through the side of the failed rib-and-board tunnel more than 100 ft beneath the river.

KUE developed the sequence and designed a receiving chamber that replaced steel and timber liner components with MTBM-digestible parts. The ribs and boards were composite members made from Hobas glass-reinforced pipe. Bulkheads and low-strength grout prepared the chamber to accept the new drive. This allowed the slurry MTBM to bore into, through, and beyond obstructions that would have blocked a standard tool.

With this plan, the team avoided uncontrolled excavation around the trapped EPBM, minimized disturbance to the failed heading, and restored a controlled face in mixed ground. The approach earned the Project of the Year Honorable Mention cited by trenchlesstechnology.com.

What this means for trenchless bidders and owners

River crossings push geotechnical risk. Here are the practical points to carry into your next bid, work plan or owner procurement.

• Do not bank a drive on a single soil model. The baseline here was nearly impermeable clay at tunnel depth. Flowing sand showed up at 2,100 ft. Under a river, plan for variability and face instability.
• Define a response for open-mode exposure. The EPBM ran in open mode when the face ran. Make sure your plan states the trigger for face support, pressurization limits, and emergency steps like bulkhead installation and flood-door operation.
• Carry a viable rescue path. The team finished with a slurry MTBM, driving through the side of a failed tunnel more than 100 ft beneath a river. If your project has deep shafts or long drives, outline a secondary method and confirm shaft geometry and working room for a changeover.
• Use sacrificial, digestible materials where you may need to cut through later. KUE’s chamber swapped steel and timber for composite ribs and boards made from Hobas glass-reinforced pipe so the MTBM could cut them. If there is any chance you will need to intersect or pass through, avoid permanent steel where feasible in those zones.
• Detail the chamber sequence. Bulkheads and low-strength grout prepared the site to receive the MTBM. Spell out grout strengths, staging, and access steps in your method statement so the team can execute fast when a rescue is needed.
• Respect deep shaft risks. The station shaft was 80 ft in diameter and 120 ft deep. The drop-structure shaft was 30 ft in diameter and 110 ft deep with a 100-ft-deep drop structure. Deep circular shafts demand attention to ventilation, water control and evacuation routes. Tie your tunnel contingency back to shaft safety steps.
• Communicate equipment loss protocols. After the EPBM was lost, the team moved to redesign and rescue. Your contract and risk plan should say how to document a loss, stabilize the site, notify stakeholders, and shift to the backup method.

Owner-side actions to reduce time and risk

Owners can help contractors succeed on river crossings and deep interceptors by setting expectations and preapproving change steps.

• State acceptable alternate methods in the bid documents. The transition here to a slurry MTBM kept the project moving. Preclear a second method for long drives beneath waterways.
• Require an emergency isolation plan. Flood doors worked here. Ask for locations, activation procedures, and inspection intervals for doors and bulkheads.
• Ask for material substitution plans where an intersection may happen. Composite, MTBM-digestible supports made a difference at the chamber.
• Review shaft depths and diameters against equipment envelopes. The project included an 80-ft-diameter, 120-ft-deep station shaft and a 30-ft-diameter, 110-ft-deep shaft with a 100-ft-deep drop structure. Confirm that rescue equipment and pipes can be staged safely within those limits.

Training and next steps

If your team works near rivers, invests in microtunneling, or writes specs, add focused training to your calendar. The industry has several near-term dates listed by the same source.

• HDD Rodeo, December 2-4, 2026, Perry, Georgia.
• HDD Academy, February 18-19, 2027, Scottsdale, Arizona.
• Microtunneling Short Course, May 4-6, 2027, Scottsdale, Arizona.
• Water Finance Conference, August 3-4, 2027, Cleveland, Ohio.

Read the full project profile at trenchlesstechnology.com, including design details from Kilduff Underground Engineering Inc., Northeast Remsco Construction, and Hazen & Sawyer.

Decision takeaway: if your next crossing runs under a river or through mixed ground, price and plan a real contingency. Define the switch to slurry microtunneling, specify digestible liners where you may need to cut, and stage bulkheads and low-strength grout so a trapped machine does not trap your schedule.