City of San Luis Obispo Foothill and Margarita Lift Stations Design

The City of San Luis Obispo’s (City) wastewater collection system includes 136 miles of gravity sewer line, 3 miles of force main, 21 inverted siphons and 9 lift stations. The City has prioritized the replacement of two of its oldest lift stations: Margarita and Foothill. In each case, replacement of the existing lift station and force main is proposed with a pre-fabricated, pre-engineered wet well (fiberglass or concrete), two submersible pumps (Wemco Hidrostal or equal), site lighting, development of a new control strategy and connection of the replacement lift station to the City’s existing SCADA system, and HDPE force main. Each site is constrained by limited available property for siting a replacement station.

The Margarita Lift Station is a Smith & Loveless dry well/wet well design, and at 41 years old, is operating beyond its life expectancy of 20 years. In 2010, a condition assessment noted a high risk of failure at the station as both the wet and dry well walls were deteriorating, causing leaks and structural issues. Because of its age and condition, replacement of the lift station was prioritized including replacement of the force main. The force main is approximately 230 feet in length, and based on a pipe condition assessment, is operating beyond its useful life expectancy. The Foothill Lift Station is also a Smith & Loveless dry well/wet well design, and is over 50 years old. The force main is approximately 440 feet in length.


EXPERTISE: MKN was retained to perform services for the replacement of the lift stations including engineering design services, surveying, geotechnical investigation, easement acquisition, and environmental review/permitting.