Infrastructure Relocation for a Growing Urban Community: Juggling Schedules and Methods

In the last decade, municipal leaders of medium-sized cities across the United States have rediscovered downtown urban centers. Economic development initiatives and long-term growth once again focus on these areas. As plans for revitalizing downtown neighborhoods begin to take shape, local governments are finding that existing infrastructures are inadequate to support the utility needs of incoming commercial and residential tenants. As a result, the need for infrastructure rehabilitation and utility service expansion is in high demand.

 

Infrastructure rehabilitation in dense urban areas can be
challenging. Owners and contractors are faced with numerous issues such as
trying to minimize traffic congestion and maintain pedestrian safety throughout
the project. In order to address these concerns, open communication among
public utility companies, transportation departments, city officials, downtown
residents and business owners, and construction crews is crucial.

In addition to communication, project managers must identify
infrastructure expansion and rehabilitation methods that have a minimal impact
on downtown communities. These methods also must allow the project to be
completed in a timely and efficient manner. By ensuring clear communication and
selecting an innovative and calculated construction approach, cities can
quickly expand their infrastructure to make way for new growth and economic
development.

The City of Knoxville, Tenn., now is successfully facing
these issues as it works toward a crucial deadline in a major downtown
revitalization project. The following account of Knoxville’s experiences
provides insight into the process, its challenges and the potential community
impact.

Knoxville is the third largest city in Tennessee and is in
the midst of revitalizing its downtown infrastructure. In June 1999,
construction began on a 500,545-square-foot convention center that will be the
cornerstone in the city’s efforts to rejuvenate its downtown area. The
Knoxville Convention Center is part of a $160 million renovation planned for
the 1982 World’s Fair Park site. The selected location for the convention
center is along Henley Street between two main downtown arteries, Clinch Avenue
and the heavily traveled Cumberland Avenue.

The Knoxville Convention Center is scheduled to open on July
31, 2002, with a Junior Olympics event. Approximately 15,000 young athletes,
accompanied by their family members and coaches, will descend on World’s
Fair Park and the new convention center. The economic impact of this event alone
is estimated at $50 million. The City of Knoxville has placed the construction
of the convention center on a fast track to ensure it will be completed in time
for the event.

W.L. Hailey and Company, headquartered in Nashville, Tenn.,
was contracted by Clark/Denark-Smith, a project management group, to relocate
the existing sewer from beneath the convention center site for the Knoxville
Utility Board and the Public Building Authority. This project included
replacing approximately 2,000 feet of sewer pipe with 2,088 feet of 48 inch
Hobas pipe to provide the necessary utility service for the convention center
complex. The new line will enable the city to easily expand the system to
accommodate further growth.

 

Project Scope and Challenges

“The City of Knoxville and the Knoxville Utility Board
have invested a significant amount of time and money in the renovation of
World’s Fair Park,” said Dan Herrell, Project Engineer at W.L.
Hailey.  “On-site, there is a
great deal of energy and activity. Because the convention center is the focal
point of this downtown revitalization project, much of the emphasis has been
placed on getting the facility up and running, which means a tight, challenging
schedule.”

The tight schedule requires a number of construction
contractors to be on-site at World’s Fair Park simultaneously. As a
result, precise scheduling is necessary to avoid crews working on top of one
another.

“Weekly progress meetings provide us with an
opportunity to discuss coordination issues,” Herrell said. “When
our work will overlap with other crews’ activities or potentially
interrupt traffic, we include the outside project managers and city officials
in our planning. This ensures that there are no unnecessary construction
delays. The majority of scheduling conflicts are resolved on-site."

Within the scope of the World’s Fair Park project,
W.L. Hailey is responsible for relocating sewer lines from beneath the proposed
site of the convention center to an area outlined roughly by Cumberland Avenue,
11th Street, World’s Park Drive and Henley Street. The construction site
also includes railroad tracks that pass near the L&N Depot and Butcher Shop
Restaurant along World’s Park Drive.

 

Phase I

The first challenge of the project was installing sewer pipes
beneath Cumberland Avenue. This is one of the heaviest traveled streets
surrounding the University of Tennessee. Each year, beginning in late August,
pedestrian traffic soars as college students walk to and from businesses along
the street. In addition, when college football season begins in September, the
vast majority of the 106,000 fans walk along Cumberland Avenue to and from
Neyland Stadium, the largest on-campus stadium in the nation. In order to avoid
unnecessary traffic congestion, W.L. Hailey chose to tunnel a portion of the
project and designed a construction schedule that focused on utilizing days
when pedestrian and vehicular traffic was lighter.

In May 2001, W.L. Hailey began excavating a
24¢-diameter, 28¢-deep shaft, starting from the southern end of the
project along Cumberland Avenue. From within this shaft, a 10 foot
cast-in-place concrete junction box was constructed around the existing
42 inch sewer line.

Lennut and Company, Inc., a subcontractor for W.L. Hailey,
bored a 1,240 linear foot, 6 inch-wide tunnel, a portion of which spans
beneath Cumberland Avenue. As work proceeded, liner plates were utilized to
support the tunnel.

“In this area, the difficulty of the project was
compounded by the existing infrastructure of commercial buildings,” Herrell
said. “Services had to be carefully identified prior to construction.
W.L. Hailey utilized plans developed by the engineering firm Barge Waggoner
Sumner & Cannon and contracted with Tennessee One Call to pinpoint the
location of existing utilities.”

Along Cumberland Avenue, exploratory excavation was required
to identify the exact location of water lines. The remainder of the excavation
process consisted of pot holing to locate the existing underground
infrastructure.

In December 2001, the 48 inch pipe was installed inside
the first phase tunnel. As the final lining of the tunnel, the pipe will be
grouted into place.

Phase II

During the second phase of the project, crews installed the
section of the 48 inch sewer pipe that runs parallel to the railroad tracks between Clinch Avenue and the L&N Depot Office and Butcher Shop Restaurant. For
this portion of the installation, W.L. Hailey chose an open-cut construction
method, utilizing a CAT 375 Excavator. After the pipe was installed and the
trench backfilled, a cold mix asphalt was poured over the trench to provide a
temporary surface as work on the remaining portion of the second phase
proceeded. The temporary surface eased traffic congestion around the job site
and enhanced safety for pedestrians traveling in and around the work area.

Another interesting challenge was the need to coordinate the
construction schedule around pick-ups and deliveries at the Knoxville Museum of
Art that is located adjacent to the project site. W.L. Hailey worked with
museum officials to time construction around the museum’s shipping and
receiving schedules.

Phase III

W.L. Hailey currently is working on the final phase of the
project, which began in October 2001. During this phase, Lennut and Company is
utilizing a tunnel boring machine to bore a 6 foot-diameter tunnel, measuring
220 feet long. The tunnel runs from the opposite end of the open-cut portion
of the project, closest to World’s Fair Park Drive and the Knoxville
business district.

The starting point for the tunnel is located within a tight
easement (35 feet), making it impossible to sink a shaft straight down to
commence boring. A typical easement for a similar project would be at least
50 feet. Consequently, W.L. Hailey excavated a 15 foot-wide, 30 foot-deep
trench inside the easement parameters and began the tunnel from the bottom of
the trench.

At the end of the tunnel, W.L. Hailey will construct a
30 foot-diameter, 25 foot-deep shaft at the edge of the business district.
From within this shaft, crews will construct a 10 foot cast-in-place junction
box to divert flow from the existing sewer line into the new line.

 

The Final Picture

W.L. Hailey is on target to complete the sewer line
relocation for the Knoxville Convention Center by the May 2002 deadline. Once
the project is finished and the 48 inch sewer main is in place, W.L. Hailey
will divert sewer flows into the new structure. The old line will be abandoned
and filled with approximately 650 cubic yards of grout.

“As business districts and downtown areas are
revitalized and infrastructure continues to age, reconfiguring and replacing
sewer lines will become increasingly necessary,” Herrell said. “The
World’s Fair sewer relocation project is a good model for owners
considering sewer rehabilitation or relocation. Decision-makers who are faced with
expanding or rehabilitating infrastructure within urban environments must
identify construction methods that will allow the project to be completed on
time while minimizing unnecessary interruptions to pedestrian and vehicular
traffic. Tunneling is one of the methods that should be considered when
beginning similar projects involving heavily traveled roadways.”

W.L. Hailey is one of the largest environmental construction firms in the United States and is ranked in the top 20 for water and storm water management services. It has offices in Atlanta, Ga., Birmingham, Ala., and Nashville, Tenn.

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