2019 Top Jobs Trenchless Technology Category: ORI Emergency Rehab Project

ORI Emergency Rehab Project
[EDITOR’S NOTE: In each issue, Utility Contractor will profile NUCA’s Top Job winners. These projects present the association’s best and most innovative work that keep our country’s utility networks operating at peak performance. To nominate your project for Top Jobs, visit: nuca.com/topjobs]

Routine sewer asset inspections by MSD revealed corrosion damage in portions of the 84-in. concrete, arch shaped, Ohio River Interceptor (ORI). The ORI, originally constructed in 1958 with traditional hand mining tunneling methods utilizing steel ring beams and wood lagging, runs through the heart of downtown Louisville, Kentucky’s business, entertainment, and hospitality district along historic Main Street.

Detailed studies of the ORI by MSD estimated that certain sections of the more than 20-ft deep sewer between 4th Street and 7th Street had significant concrete loss approaching the full depth of the original 12-in. cross section. Despite the impact to downtown businesses, commuters, and tourists, MSD closed portions of Main Street to protect the public from any collapse, while simultaneously reaching out to the design and contracting community for immediate assistance.

Ulliman Schutte Construction and Brown & Caldwell were ultimately hired by MSD under an emergency procurement to design and to expedite the repairs while minimizing impacts on the community. The project team (USC, B&C and MSD) rapidly developed an in-situ rehabilitation plan that utilized a single existing access point at the 4th and Main Street intersection. Flow diversion plans were jointly developed and field tested to send minor portions of the flow through alternate facilities. However, since the ORI carries approximately 40% of MSD’s flow to its treatment center, a significant portion of the flow had to be pumped around the section to be rehabilitated.

Diverting this substantial flow to a temporary pumping station required several gate replacements, gate upgrades, and temporary bulkheads. Temporary pumping was accomplished via 7 each 18-in. centrifugal pumps from Thompson Pump that utilized an efficient blend of silent diesel and variable speed electric power. The temporary pump station was manned 24 hours per day and operated in close coordination with MSD’s other facilities to deliver approximately 40 mgd through 4 each 18-in. HDPE discharge pipes strategically routed around downtown to avoid inconvenience to the general public.

After the incoming flows were diverted, approximately 1,400 lf of the ORI was rehabilitated, via man entry, with PVC strip liner panels from Danby installed by Boyer Inc. The ORI was water blasted at 10,000 psi to remove any loose concrete and debris. Local flows were internally controlled and diverted within the existing sewer as sections were reinforced and the PVC liner was installed to permanently protect the rehabilitated section from future sewer gas corrosion.

Grout was then injected into the annular space between the PVC liner and the existing pipe to form a new cross section in accordance with ASTM F1698-02. During this work a void under Main Street was discovered which presented significant dangers to the workers below the suspended street and to the public topside. Additional trenchless methodologies were employed to repair the sewer collapse with robots and ground stabilization from above while installing steel ring beams and lagging within the affected sewer section for worker protection from below.

In addition to the mainline ORI trenchless repair, MSD elected to mitigate three downtown Combined Sewer Overflows (CSOs) as part of this project. The project team accomplished this goal by installing three new trenchless connections into the ORI. The side street shafts for drop structures and tunneling work were completed by Midwest Mole with no community impacts along Main Street. 42-in. Hobas piping was direct bored in one instance and steel casing pipes with 42-in. Hobas carrier pipes were utilized in the others. All three blind (no receiving pit), underground connections to the ORI were completed in perfect alignment utilizing underground soil stabilization for bracing and sealing during the connection work.

One of the major challenges was related to the tight working areas for the access points to the ORI as well as the points for the elimination of the CSOs. The job took place in the heart of the city that was founded on the banks of the Ohio River in 1780. With this age, the amount of infrastructure buried in this area was a challenging portion of installing the access points for this large rehabilitation project and required close coordination with all other parties who had infrastructure buried in the work area. The shafts for mining in the new connections to the ORI were extremely small and required very short sections of pipe for the installation.

“As a public entity, we are tasked with being diligent stewards for our ratepayers. The collaborative nature of this project has proven to be fully supportive of this mandate,” wrote Heather Dodds, P.E., Regulatory Compliance and Asset Management Administrator for MSD. “Despite the numerous setbacks associated with record rain events and river flooding, the project was completed within its original schedule and budget without any recordable or lost time accidents.

“Flow capacity within the ORI was restored such that it was confidently placed back into service for generations to come. The project not only succeeded, it surpassed all expectations by every measure in terms of solution optimization, collaboration, flexibility, quality, delivery time, cost savings, impact to community/stakeholders, partnering and teamwork.

“In short, MSD accomplished all of our initial goals and many more. This project has been a shining example of the advantages of collaborative emergency utility repair.”

Project At-a-Glance

Category: Trenchless Technologies

Utility SubContractor: Midwest Mole

Owner: Louisville/Jefferson County Metropolitan Sewer District (MSD)

Location: Louisville, KY

Project Safety: No Recordables and No Lost Time Accidents

Project Duration: May 4, 2018, through Dec. 31, 2018 (241 Calendar Days)

Project Cost: $18 million

Contracting Method: Hybrid Design-Build

Engineer of Record: Brown and Caldwell (B&C)

Contractor: Ulliman Schutte Construction (USC)

Owner: Louisville/Jefferson County Metropolitan Sewer District (MSD)

Notable Specialty Subcontractors: Midwest Mole Inc., Boyer Inc., Thompson Pump

Notable Suppliers: Danby PVC Lining, Hobas Pipe

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