Rehab Of A 100-Year Old Brick Storm Sewer

U-TECH
By Datta Shirodkar, Boyer Inc. and Michael Spero, P.E., Danby LLC | July 2010 Vol. 65 No. 7

In what should have been a relatively simple project with a few significant yet manageable challenges, circumstances quickly changed to create the “job from hell.”

This sewer rehabilitation project is located in the southwest sector of Washington, DC. What was at one time the USEPA building was demolished and the site is being developed for mixed use. The Waterfront Mall Project will contain retail stores, restaurants, offices and residential units. Through the middle of the site there is an existing 100-year-old, 90-inch diameter storm sewer about 800 feet long. About half of the length of pipe is all brick, consisting of three layers. The other half of the pipe consists of a bottom portion constructed of brick (below the spring line) and the upper half is unreinforced concrete. The pipe makes one 90 degree short radius bend about mid length.

The sewer is now a storm drain but previously it was a combined sewer. It empties into the Potomac River about 1,000 feet downstream of the project site. The sewer is owned and maintained by the District of Columbia Water and Sewer Authority (DCWASA). The new development included the proposed construction of a building and a parking garage over the existing sewer. Although the sewer was in relatively good condition, especially after 100 years of service, DCWASA requested that the sewer be rehabilitated by the developer. This was primarily due to the fact that access to the pipe would be severely limited after the buildings were constructed which would diminish the ability of the owner to maintain or repair the sewer.

It was decided to use the Danby lining system to rehabilitate the sewer. This is a grouted-in-place-liner (GIPL) which has proven experience in the U.S. for over 20 years. This lining system consists of 12-inch wide PVC panels delivered to the site in 300 foot coils. This is a man-entry system so the pipe needed to be dry. Access to the pipe interior was relatively good since there were existing manholes at the upstream and downstream limits of the rehab section. A new manhole about midway had been constructed. The installation contractor was Boyer Inc. of Houston.