DC Water’s Rehabilitation of Potomac Interceptor Manhole 31 (MH31) replaced a deteriorating wastewater structure built in 1963 that conveyed approximately 90 million gallons of wastewater per day from surrounding jurisdictions. Left unaddressed, the failing structure posed a significant risk to regional wastewater conveyance and the drinking water of two million people in the area.
The project’s complexity made early collaboration particularly important. The interceptor had to remain operational throughout construction, while the team worked in a sensitive park environment near residential communities and the Potomac River, with limited access, deep excavation and uncertainty about existing infrastructure.
A First Foray into Progressive Design-Build
The project also represented an important organizational milestone: MH31 was DC Water’s first Progressive Design-Build (PDB) project.
DC Water spent approximately two years preparing for PDB implementation by training more than 100 staff and developing new procedures and contract documents. After this preparation, the Owner, designer, builder and specialty partners operated as an integrated team. Weekly working sessions brought technical experts together to resolve issues, evaluate alternatives and make informed decisions.
This collaboration led to the development of an “in-the-dry” approach that reduced reliance on large-scale bypass pumping, minimized environmental impacts and maintained continuous wastewater conveyance. And when inspections revealed that the existing interceptor was more deteriorated than expected and was at imminent risk of collapse, early collaboration allowed the team to incorporate an innovative steel slip-lining before new construction began, avoiding continuous bypass pumping and reducing overflow risk to the Potomac River.
DC Water successfully completed its first successful PDB project approximately four months ahead of its contracted completion date and $1 million under budget. As a result of DC Water’s commitment to comprehensive design-build training, more than 40 of its professionals now hold a DBIA credential.
Design-Build Team
| Client/Owner: | DC Water |
| Owner Advisor: | Ramboll |
| Design-Builder: | Ulliman Schutte Construction |
| General Contractor: | Ulliman Schutte Construction |
| Engineer: | Brown and Caldwell |
| Specialty Contractors: | Com-Bro Contracting; Stocks General Contractors; Midwest Mole; DP Consultants; Savin Engineers |
| Project Cost: | $40,500,000 |
| Construction Duration: | 44 months |
Photos
Photo Credits: Ulliman Schutte Construction; DC Water; Brown and Caldwell