SAWS Rio Grande 24” Water Main Replacement

Pipe Burst Creates Necessary Change for 70-Year-Old Transmission Main

Project Purpose

The existing 70+ year old 24-inch transmission main in N. Rio Grande near the AT&T Center is experiencing numerous main breaks due to age and condition. SAWS intended to construct the line through open cut using an unspecified construction contract. During the design phase, SAWS Operations alerted the design team to the cyclic pressure surges in the project area and resulting pipe repairs. Operations inquired about the feasibility of utilizing pipebursting to replace the water main instead of open cut construction. KFA evaluated pipebursting and determined that it was feasible for this water line and economically competitive with open cut construction. KFA developed plans and specifications for both open cut and pipebursting options, and aided SAWS in evaluating this construction technique.

Project Approach

SAWS asked KFA to design the replacement of approximately 4,270 LF of 24” water transmission main that was in poor condition along N. Rio Grande. KFA developed the project schedule, wrote the PER, designed the horizontal and vertical alignment and led meetings with SAWS. The KFA team coordinated with the city of San Antonio’s ROW department to determine the existing Pavement Condition Index for each block of the project and incorporated appropriate street restoration approaches into the project to meet the city’s Street Cut Ordinance. Although SAWS is very familiar with pipebursting for sanitary sewer lines, pipebursting potable water mains is not a standard practice for SAWS. This project is considered a pilot project to evaluate the merits of pipebursting potable water mains. Since pipebursting potable water mains is not a widespread practice in Texas, there is a limited pool of Texas based contractors with experience bursting water mains of this diameter. KFA is developing contractor qualifications to establish an adequate minimum level of experience while still obtaining a suitable number of competitive bids.

Project Results

Construction of this project will begin in late 2018. KFA has developed plans for both open cut replacement and pipebursting, which will allow SAWS to compare prices for each construction method on the same project. KFA’s work evaluating HDPE pipe materials for this project has resulted in SAWS electing to allow HDPE as a water main pipe material in their system.