Todville Sanitary Sewer Improvements
CobbFendley was responsible for the pipe bursting approximately 7,000 linear feet of 12” sanitary sewer gravity main along Todville Road from East Meyer Avenue to Brummerhop Street. The project included removing and replacing sanitary sewer manholes, replacing sanitary sewer crossings under Todville Road, reconnecting all existing sanitary services to the proposed sanitary sewer lines, dewatering, replacement of driveways, and pavement as necessary to construct the gravity mains, storm water prevention, and traffic control.
The existing sewer gravity line was in need of a complete replacement due to the high amount of infiltration from storm water, bay water (saltwater) and groundwater. During heavy rain events or high tides the Main Street WWTP plant would see a spike in flows as a result. It was determined that the line section along Todville, which is adjacent to Galveston Bay, was a main contributor because plant operators would notice the salinity of the water being delivered to the WWTP. Prior to design, CobbFendley discussed with City Staff the need to video (CCTV) the proposed section of pipe in order to determine the locations were water was infiltrating the system and verify the condition of the line. The CCTV not only provided clear evidence that this section of line was in critical condition, it provided key locations where service lateral connections to the main line had failed, intrusions from tree roots were located and where pipe joints were separating. It was also clear that the existing manholes had reached their life expectancy.
Because the entire line needed to be completely replaced, we initially envisioned removing and replacing the line in its current location in sections, using bypass pumping to divert the flow around the working sections. Because of the limited right of way, surface conflicts and heavy traffic conditions we determined that we could limited the amount of surface disruption by pipe bursting the existing main line. For the most part, we were able to use the existing manhole locations as bore pits for the pipe bursting process, which reduced amount of surface disturbance. Services connections were bored under the existing roadway, in order to keep traffic moving and reduce the amount of pavement repair needed. Because Todville Road is a Harris County roadway, coordination regarding pavement repairs and traffic control was important and critical to the complete of the project.
Managing the groundwater and surface water during months of record rainfall provided unforgiving challenges in constructing the manholes. Dewatering and sheet piling around the proposed manhole locations provided great solutions to managing those challenges.