Sewer Rehabilitation Project

Castle Rock Water staff identifies sewer pipes for rehabilitation based on a history of root intrusion, increased annual maintenance and pipe defects identified by closed circuit televised (CCTV) inspection. Sewer pipes with capacity issues are also identified as candidates for replacement with larger pipes. Engineering staff develops plans for rehabilitation based on the severity of the defects found.

Cracked sewer pipes can often be repaired from within by pulling a new liner through the sewer pipe. The in-situ method of cured-in-place pipe lining has been in practice since the 1970s and involves pulling a resin-saturated felt tube into the damaged sewer pipe. The tube is then expanded and cured into a new tight-fitting, joint-less pipe within the existing sewer pipe. Cured-in-place lining can extend the service life of sewer pipes by 50 to 75 years. Rehabilitation by the installation of a cured-in-place liner, before the sewer pipe deteriorates is cost-effective, and can be completed with minimal disruption to service and results in less future maintenance.

Severe sewer pipe defects and undersized pipes must be dug-up and exposed in order to complete the repairs. When completed on short sections of pipe, these are referred to as "open-cut point repairs." Sometimes a few critical open-cut point repairs must be completed in advance of CIPP lining a long stretch of sewer pipe.

Woodlands manhole rehabilitation project

Phase 1

From fall 2020 to spring 2021, Castle Rock Water replaced seven manholes on the Woodlands Sewer Interceptor pipeline. The pipeline was constructed over 30 years ago, and the concrete manholes had fully degraded due to corrosive sewer gasses. The contractor installed fiberglass-reinforced polymer manhole inserts within the existing sewer manholes. The advantage of this rehabilitation method is the majority of the existing concrete manholes were replaced with a polymer manhole in its existing location. This minimized the amount of overall excavation and construction. The end result is all new manholes that are highly resistant to corrosion from sewer gasses.

Phase 2

Phase 2 was completed in 2022, and it was done as a result of Castle Rock Water staff inspecting and assessing 25 manholes on the interceptor downstream of Phase 1. These manholes are located adjacent to the paved pedestrian trail from Black Pine Drive to Woodlands Boulevard. The condition of these manholes varied from high levels of concrete corrosion with failed existing manhole liners to manholes with lower levels of concrete corrosion. The rehabilitation approach to this phase required a variable approach utilizing different rehabilitation technologies. Staff published a request for proposals in October 2021, and six proposals were received. Town Council awarded a contract in the amount of $960,095 to C&L Water Solutions in December 2021.

The 330-day project kicked off in early 2022 and the contractor completed manned-entry comprehensive inspections of all of the manholes. The most severely corroded manholes in this phase received the same FRP inserts that were installed in Phase 1. Other manholes were cleaned and rebuilt with corrosion-resistant lining systems.

The major construction work began in July 2022 and was substantially completed in December 2022. There were some temporary trail closures necessary for public safety during construction, but the trails are now open again. Site reclamation and restoration was completed in Spring 2023.