Concrete Cloth Stormwater Infrastructure
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Washington, DC
GeoSpray® Geopolymer Mortar: 72" Brick Sewer Rehabilitation

Project Overview
DC Water’s engineering group implemented a pipe entry inspection after receiving an alert from the District Department of Transportation to verify the integrity of a 72” diameter brick sewer.  This was located at the F Street NW block between 12th and 11th streets. DDOT had done a bore-hole inspection at a street depression which revealed a 20” deep void under the pavement.  
Prior to entering the sewer, DC Water evaluated their records and noted the Metro subway tunnel runs below the length of 12th Street and the 72” brick sewer runs above the tunnel.  In addition, in the 1970’s, a 188 foot section of the 72” brick sewer was offset and replaced with 205 feet of 72” Reinforced Concrete Pipe. The entry inspection showed the replaced 72” RCP was in great shape, however, the original brick sewer was a different story. Starting at the interface with the RCP, the brick crown was cracked and propagating east toward 11th Street and west toward 13th Street. It was considered that the cracking likely developed after the construction of the Metro Subway system.
The most severe damage was located between 12th and 11th Streets where the crown was cracked and missing bricks. Fortunately, there was no significant oval deformation, and there were not many open mortar joints which would be typical of an impending pre-sink-hole collapse scenario.


Solution
DC Water evaluated several repair options including CIPP and tunnel plate.  The CIPP option was eliminated due to the need to remove manholes in a busy intersection and issues with reinstating flow daily.  The tunnel plate was eliminated due to cost considerations.  In the end the city specified two different spray applied applications and awarded the project to Inland Pipe Rehab (IPR) to line with GeoSpray® geopolymer mortar.   
The rehabilitation required: 1) a 50 foot full structural repair section that was missing bricks and showing signs of advanced crown deterioration and 2) a 125 foot long partially deteriorated section that needed to stop inflow and infiltration (I&I) and provide some structural support to the bricks and missing mortar.  After further inspection, DC Water requested a change order for a full structural repair of the entire 175 feet of pipe. 

 Click here to read the full study.

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