Rehabilitating Early 20th Century Bricks and Mortar Sewer with 21st Century Products

The City of Effingham's long term control plan (LTCP) identified the condition of their 2,100-foot-long (640 m), brick arched sewer as contributing to combined sewer overflows (CSOs). Flow monitoring data recorded at the overflow indicated that the brick arched sewer may be contributing to the inflow and infiltration (I/I) problem. As a part of their due diligence, the City Engineering Department did some investigating to learn more about the brick arched sewer. From a time capsule in the old city hall dated 1910, there was mention of the labor costs associated with extending the sewer. Through further investigation of Effingham records, City staff discovered plans for the repair of the sewer in the 1950s and 1970s. However, even with the plans available, they were not sure of the sewer alignment and could only speculate as to its condition. The City was sure that the sewer was built in a former creek bed and was extended as Effingham continued to grow. Although the sewer is described as “brick arched,” there a few sections that are circular and some sections constructed of local stone. Dimensions of the brick arched sewer vary from being 48 inch (1.2 m) circular at the upstream end to 6 foot – 7 inches (2 m) wide by 6 foot – 6 inches (1.9 m) tall at the downstream endEffingham enlisted the services of Crawford, Murphy & Tilly, Inc. (CMT) based on the engineering consultant's experience with evaluating and rehabilitating sewer collection systems. Evaluation consisted of televised inspection, field surveys, review of historical data and, eventually, manned entry inspection. Televised inspection utilized a transponder on a camera that sent signals to grade so that the alignment of the sewer could be surveyed using state plane coordinates. After plotting the sewer alignment onto the City's aerial mapping, it was apparent that three structures - two houses and a warehouse - were constructed over the sewer.Having residential and commercial structures located over a brick sewer that was at least 100 years old changed the focus of the project from reducing I/I to ensuring the structural stability of the sewer. To ascertain the urgency of rehabilitating the sewer, a manned inspection was performed at two locations along the sewer alignment to test the soundness of the brick and mortar. Qualitative testing determined the magnitude of deteriorated mortar and loose bricks. With this new information available to the city, it was decided to rehabilitate the entire length of brick arched sewer so as not to compromise the safety of the public, while at the same time reducing infiltration potential and improving corrosion resistance.Due to the varying sewer dimensions, cured-in-place lining was not feasible and relocation was cost prohibitive. An in-situ rehabilitation product was needed that could encapsulate the interior of the brick arched sewer and provide the necessary structural strength to support the live and dead loads. This presentation will elaborate on the search for a rehabilitation product that would meet all of the design criteria, locating a qualified spray epoxy contractor and the lessons learned along the way.