“No-Dig” Ceremony at the Overland Park Arboretum and Botanical Gardens Focuses on the Environment

JCW to Drill 88-inch Diameter, 3,330 lf Tunnel Under the Arboretum to Accommodate 60-Inch Diameter Gravity Sewer, Protecting the Environment of this Special Asset for All in the Kansas City Area to Enjoy

Overland Park, Kan. (August 3, 2009) – Tunneling was selected to replace open-cut trenching as the method for constructing 3,330 linear feet of 60-inch diameter gravity sewer under portions of the Overland Park Arboretum and Botanical Gardens in Overland Park, protecting the environment and preserving the beauty of the Arboretum for all in the Kansas City area to enjoy. Johnson County Wastewater (JCW), which is constructing the new sewer, serves more than 130,000 customers in Eastern Kansas with more than 2,100 miles of sewer line.

The 3,330-linear-foot tunneling project is part of 37,000 linear feet of new gravity sewer being constructed in the Blue River Watershed. When completed in late 2010 or early 2011, the $18 million Blue River 26 project will open up the area roughly from Pflumm Road to Switzer Road and 175th Street to 183rd Street for development. As additional sewer line is built, drainage will flow to the Blue River 26 trunk line, ultimately serving a 25-square-mile area bounded approximately by 175th Street to 199th Street and Antioch Road to Spring Hill.

The Tunnel Boring Machine (TBM), fabricated by Southland Contracting, Inc., of Ft. Worth, Tex., the tunneling contractor, was put into place over the weekend of August 1 and 2. Eighty-eight inches in diameter, 20 feet long, powered by two, 200-hp diesel engines, and guided by a laser targeting system, it is scheduled to excavate an average of 31 feet of material, primarily limestone and shale, each day at depths of up to 74 feet. The excavation of the tunnel is expected to take approximately 106 days.

According the JCW Project Manager Stuart Lord, PE, this isn’t the first time the tunneling method has been employed by the utility. “But we haven’t done a tunnel of this magnitude with the idea of preserving the parkland above,” he said. “In our desire to protect the park, open-cut trenching, which would have taken with it mature trees, plants, and other features of the site, was not the preferred method of construction.”

Instead, the team of JCW, GBA Architects and Engineers, a Lenexa, Kan.-based full-service engineering and architectural firm that is engineer-of-record on the Blue River 26 project, and PB Americas, Inc. decided to go underground to protect this important public amenity. According to Lord, while tunneling is more expensive than open-cut trenching, the savings in terms of both the natural and built environment are significant. These benefits range from reduced stormwater runoff, improved air quality, reduced carbon dioxide, and noise reduction to preserving the beauty of the site, and the intangible personal and social benefits.

Lord noted that the cost of the tunneling portion of the project is approximately $5.9 million. While he acknowledged that open-cut trenching would be less expensive, possibly about $1 million less, it would still be relatively expensive because of the terrain and the required depth of the sewer line.

Work on the tunneling project is scheduled to begin immediately, with installation of sewer line within the tunnel scheduled for completion in mid-April of 2010.

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