8
Environmental Agencies Involved in Permitting
15
Special-Status Plant Species
14
Special-Status Wildlife Species
Navigating an environmentally sensitive project site
The inspection, assessment, and resulting rehabilitation of this sewer trunk was inherently challenging due to its location along the Napa River, in an area which is critical habitat for 15 special-status plant species and 14 special-status wildlife species. This required Woodard & Curran’s experts to collaborate with eight different environmental agencies to ensure all permitting was procured for the project to move forward. In addition, the Woodard & Curran team acquired the state’s environmental clearance under the California Environmental Quality Act (CEQA) to perform the work.
The design plans detailed distinct areas at each manhole site where contractors could safely work without impacting sensitive environmental areas along the existing alignment. This helped the contractor identify where best to deploy their crews for the CIPP work while still meeting stringent permit requirements. Certain manholes located within highly sensitive environmental areas were designated as lining reception locations to minimized or totally avoid impacting environmentally sensitive habitats.
Another critical environmental consideration the design team had to account for was the large volume of cure water necessary for the rehabilitation project. Given the drought status in California, this was a significant demand on water resources. However, the team worked with the client to leverage recycled water resources produced by NapaSan to help mitigate exacerbating drought conditions. A mobile filtration system was used for the cure water prior to discharging to the sewer system to comply with the maximum allowed styrene concentration levels at NapaSan’s treatment plant.
Minimizing impact to a heavily trafficked area
In addition to sensitive environmental habitat, the trunk sewer’s alignment also follows the Napa River Trail, a paved walkway providing area residents with recreation access, such as hiking, birdwatching, and fishing. The project team collaborated with a myriad of stakeholders and the construction crew to reduce impact to the trail for both public access to the resource and public safety.
The bypass required to ensure sewer service was not disrupted for ratepayers met an additional hurdle with an active railroad crossing. The bypass piping had to be manifolded and truncated to one 22-inch diameter HDPE bypass pipe. This allowed the bypass to fit inside an existing 24-inch diameter storm drain to cross through a wetland area and travel under active railroad tracks so as not to disrupt rail service. Similar measures were taken to reduce impacts to area vehicular traffic.
