The Contra Costa Water District’s Ralph D. Bollman Water Treatment Plant (Bollman WTP) was constructed in 1968 and is located in Concord, California. The Bollman WTP supplies clean and sanitary water to the general public for drinking and other purposes. The recent plant upgrade of $35 million will allow Contra Costa’s 430,000 customers to continue to receive the highest quality water and the most reliable service possible.
A portion of the overall project was the $4 million basin improvements that included the installation of an outflow pipeline. The 12” outflow drain line and valve needed to be installed on a hillside, with depths ranging from 0-17’ and running over 40’ in length. The difficulty was the route the pipeline had to take. There are two existing structures, one built on the top of the hillside, and the second built into the side of the hillside, which is the flow lift station. The excavation cut directly into the hillside between the two structures, paralleling and below the lift station.
Les Campbell of GSE Construction Co. Inc was concerned that the excavation to add the pipeline would disturb the Flow Lift Pumping Station and the other building that are on the same hillside. The workspace required for the workers and the pipe was a width of 4’ID. Les called Trench Plate® Rental Co in Pittsburg for the shoring equipment he would need on the project. Trench Plate® Rental Co suggested the use of steel shields stacked at a 90-degree angle with steel plates across the outside angle to allow efficiency and safety. The steel shields gave the workers the ability to stack the boxes to the height of the hillside and to use more boxes for added protection.
The combination of shields and steel plates, not only worked well to protect the excavation, as well as the hillside and foundations of the adjacent buildings, it aided in the completion of the project by allowing the work to move forward efficiently. The addition of the drain line aids the efficiency of the overall station. Currently they must use portable temporary pumps to drain the station.
Contra Costa Water District policies and procedures ensure that only contractors with good safety programs are selected to work at the plant. The contractors must be evaluated on contractor performance, learn about safety requirements, process hazards and emergency response procedures so they can complete the work safely. By working together with Trench Plate® Rental Co, GSE exceeded all of the requirements placed on them by the Water Treatment Facility