Part II: Three environmental projects snare APWA Project of the Year awards

A trailway extension, relief trunk sewer and an ocean outfall top the list this year as the leading public works projects in the environment category. Read why the American Public Works Association chose to honor them.

Here at Public Works Online, we are reviewing the top public works projects across the nation as selected by the American Public Works Association. Part I looked at the three winners in the structures category. Part II focuses on projects that benefit the environment.

The four categories include structures, environment, disaster or emergency construction/repair, transportation, and historical restoration/preservation. The project costs range from less than $2 million all the way up to more than $10 million.

The environmental winners include:

• Ellicott Creek Trailway Extension (Amherst, NY)
• Salt Valley Relief Trunk Sewer (Lincoln, NE)
• South Bay Ocean Outfall (San Diego, CA)

Preserving the environment and providing recreational space were the two goals when the Ellicott Creek Trailway Extension Project was initiated.

The town hired URS Greiner Consultants, Inc. with Visone Construction as the primary contractor to build the more than 8,400 lineal feet of 10-foot wide asphalt recreation path connecting to the existing Town of Amherst and the Ellicott Creek Trailway.

Included in the project was the creation of a pond/wetland area to be used for fishing, passive recreation, and to provide a scenic vista for trail users. It also plays a major role in drainage and flood prevention.

During the construction, a temporary bulletin board proved very successful in keeping the residents informed of the construction activities. After the project was completed, a permanent community bulletin board was built detailing the trail system and pointing out various facilities.

Much emphasis was also put on making all the facilities accessible to the handicapped.

After evaluating numerous alternatives to improve sewer service and allow for more growth, the City of Lincoln Public Works Department determined to design and construct a new relief sewer to parallel the existing system.

The city hired Montgomery Watson as consultant and Garney Companies as primary contractor to lay the new 78-inch diameter line. It is destined to help carry existing flows as well as any that will be added until the year 2020.

Environmental concerns were to protect Antelope Creek and nearby Salt Creek. Antelope Creek was crossed with an inverted siphon, requiring a 15-foot deep excavation across the entire width of the channel and into the steep banks. The challenge was to maintain a large excavation while allowing streamflow to pass. This was successfully accomplished with a combination of cofferdams and sheet piles.

Once the construction was finished, the creekbanks were restored to a more stable condition than existed before the project.

The use of electromagnetic instrumentation to identify the limits of a buried streambank protection is believed to be the first use of this method for this type of application.

During construction, since line-of-sight communication was not possible, workers were provided with wireless headsets that allowed them to communicate and work hands free. This resulted in a more accurate control of grade, higher production, and a safer working environment.

This project fell into the $2 to $10 million category.

Huge pipe sections were lowered to the ocean floor to become part of the highest pressure tunnel ever built in North America.

The South Bay Ocean Outfall, jointly owned by the International Boundary and Water Commission and the City of San Diego, has been the recipient of several awards this year. In addition to the APWA award, it was a merit finalist in the project of the year competition with the American Society of Civil Engineers.

The huge, more than $10 million category project consisted basically of an underground tunnel extending to 13,500 feet offshore where it surfaces and continues along the sea floor ending in a Y-shaped structure and two diffuser legs approximately 3.5 miles offshore at a depth of 95 feet.

The primary consultant, Parsons Engineering Science, Inc., and the primary contractor, Traylor Brothers/Obayashi, Joint Venture, pushed the "state-of-the-art" envelope for difficult tunneling conditions. The project incorporated a universal tunnel boring machine and a unique one-pass segmented liner.

An added challenge in building the tunnel was to make certain that the pipe is not damaged in the future by seismic activity.

The project set four records:

• The largest victaulic couplings (144 inch)
• The largest bonneted knife gate valve (144 inch)
• The longest screw conveyor (125 feet)
• The largest diameter-driven casing (14 feet)

Additionally, the tunnel is the highest pressure tunnel ever built in North America and the third highest in the world.

Watch for future articles spotlighting other winners in the disaster or emergency construction category, the historical restoration/preservation category, and the transportation category.

By Joyce Everhart
Editor, Public Works Online