Page 18 - Sept/Oct 2018 Vol 36 No 3

OAK RIDGE By Steve Bostic, P.E.
EQ System Addresses Requirements

The City of Oak Ridge, Tennessee, was planned and
constructed as a part of the “Manhattan Project,” an important
part of the development of the atomic bomb during World
War II. The majority of the city’s infrastructure, including its
wastewater collection system, was constructed in the 1940s. The
collection system includes hundreds of miles of concrete and
clay pipe and brick manholes which, over their more than 70
years of service, developed numerous leaks leading to increased
inflow and infiltration (I&I) into the collection system. The
Environmental Protection Agency (EPA) ultimately issued
a consent order that mandated that the City of Oak Ridge
eliminate overflows from their wastewater collection system.
The overflows were being caused by I&I occurring with rainfall
events. Based on the requirements outlined in the mandate,
overflows due to the two-year/24-hour rainfall event had to be
eliminated.

The cause of the overflows

The highest flows were occurring in the eastern portion of
the wastewater collection system, where the oldest pipe and
manholes are located.

The eastern portion is comprised of three main drainage sub-
basins: the East Plant basin, the Emory Valley basin, and the Y-12
(Scarboro) basin. The flow from the three sub-basins discharges
to the main interceptor at a point in the downtown area referred
to as the “junction” in our design. The East Plant and Emory
Valley flows are transported via force mains and discharge to an
interceptor upstream of the junction, while the Scarboro basin
flows are transported via gravity to the junction.

High flows at the confluence of these three interceptors in the
eastern portion were overloading the main interceptor leading to
the wastewater treatment plant.

Developing a solution East Plant (top), Scarboro (middle), and Emory Valley (bottom).

To better understand the problem, City of Oak Ridge EQ Basins
the LDA Engineering team, led by System Schematic
Steve Bostic, P.E. and Greg Jones, P.E.,
developed a computer model of the
collection system. Using the computer
model, they then developed a plan to
address the problem by limiting the rate
of flow being discharged to the main
interceptor at the junction during the
two-year/24-hour rainfall event.

The plan centered on the development
of a comprehensive system that included
continued rehabilitation of the collection
system piping and manholes and
construction of three Equalization (EQ)
Basins. The overall goals of the plan
were to (1) automatically divert, collect,
and store wastewater during times of
high flow to reduce peak flows in the
collection system, particularly in the main
interceptor downstream of the junction,
and to (2) automatically return the stored

18 TPW September/October 2018