The City of Sacramento Department of Utilities has been
systematically evaluating dozens of sewer basins through master planning
efforts, starting with top priority basins.
Boyle Engineering Corporation provided master planning, hydraulic
modeling, cost estimation, and report preparation services on one such basin
project. PIZER, Inc. provided
technical assistance to Boyle Engineering by developing and calibrating a HYDRA®
model for the project.
Background: When the conveyance system was constructed in this residential area, sewer collector pipes were laid in rear-yard easements. In the intervening years, trees and shrubs have invaded, causing extensive infiltration. Also, the sewer mains were too small, causing severe surcharging.
Project Scope: The primary objective was to recommend projects to improve operations and minimize current maintenance needs in the basin. This included evaluation of existing conditions of the collection system and pump stations, identification of physical problems and hydraulic deficiencies with the facilities, evaluation of alternative solutions for problems, and recommending improvement projects.
Results: Hydraulic analyses of the existing collection system indicated that peak flows could not be conveyed without surcharging throughout the majority of the basin. Recommended improvements, including rehabilitation of portions of the collection system and construction of two alternative relief pipelines was modeled using HYDRA.
Boyle Engineering determined the reduction in infiltration and inflow attributable to these improvements, and compared the costs and benefits of each of these improvements.The City plans to implement the recommendations, including the 24-inch bypass pipeline of Scenario B over the next 3 years as part of their Capitol Improvement Program.