Municipal Projects

Hultgren – Tillis Engineers have provided geotechnical engineering services on numerous wastewater and water infrastructure projects, including pump stations, new and replacement sanitary sewers, wastewater outfalls, intake structures, maintenance buildings, lift stations, treatment ponds and embankments, treatment plants, canals and pipelines. We provide geotechnical engineering services for public administration and health care buildings and parking structures.

City of Concord Parking Structure (Concord, CA) - The parking garage is a three-level structure. Subsurface conditions included fill, alluvial deposits, volcanic ash and soft rock. The primary geotechnical concerns were the presence of expansive soil, potential variability of the ash deposit, settlement, and the possible presence of remnant subsurface structures and/or foundations. Hultgren – Tillis Engineers’ design included removal of the ash from below foundations and placing 2 feet of aggregate base below the footings to help spread the loads and reduce settlement of the column foundations.

Morgan Territory Road Emergency Repairs (Contra Costa County, CA) - A landslide occurred that cut off access to hundreds of residents along Morgan Territory Road.  Hultgren – Tillis Engineers explored the site conditions with borings and installed inclinometers to monitor the depth of the slide and rate of movement.  Based on the data collected from the exploration, Hultgren – Tillis Engineers developed conclusions and recommendations regarding the cause of the slide and potential alternatives for repairing the slide.  Hultgren – Tillis Engineers evaluated alternatives including an earthwork slope repair and various retaining wall configurations.  The repair scheme included a tie-back wall and a buried stitch pier wall.

Middle River Intake and Pump Station (Victoria Island, San Joaquin County, CA) - Hultgren – Tillis Engineers was the geotechnical engineer for all elements of Contra Costa Water District’s Middle River water intake. The project consisted of an intake structure and 320 CFS pump station, a flood protection levee around the intake structure, two miles of 6-foot diameter pipe, and a tunnel beneath Old River. As part of its assignment, Hultgren – Tillis Engineers developed geotechnical design criteria for the Open Cell® bulkhead, a temporary cofferdam, intake wetwell shoring, and tunnel launching and receiving shafts.

Contra Costa Canal Encasement Project (Oakley, CA) - Contra Costa Water District had a capital improvement plan to encase the Contra Costa Canal between the Rock Slough intake and Pumping Plant No. 1.  Hultgren – Tillis Engineers was the geotechnical engineer for the intake structure, associated flood control embankment and for encasement of the canal.  The encasement included installation of a 10-foot diameter pipe followed by backfilling of the canal.

Pittsburg Civic Center (Pittsburg, CA) - The Civic Center consists of one- to three-story high steel-frame structure for the combined City Hall and Police Station facility. Hultgren – Tillis Engineers provided geotechnical design criteria and observed foundation installation and site grading.

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