The West Travis County Public Utility Agency (WTCPUA) owns and operates a raw water intake along Lake Austin. The existing 30” transmission main feeding the Uplands Ridge water treatment plant is not sufficient. Murfee Engineering has been working on providing the WTCPUA with multiple alignment options for the installation of a redundant 30” transmission line that exceeds the demand of the growing community. This would provide the WTCPUA with a system that can be easily maintained and wouldn't require a complete shutdown of operations, which would cripple their water supply.
The existing transmission main was built approximately 30 years ago, before there was much development in the area. Now, it runs through a new development that features homes in the $600,000-$900,000 range, so following its alignment is not a feasible option. During their PER investigation, Murfee Engineering identified two options to utilize existing nature trails and run the new line along the backside of the neighborhoods, but those plans could have a negative environmental impact.
Construct-Ability was engaged to provide feasible, cost-effective conceptual estimates for the alternative alignments. We began with a site visit to take photographs and identify conditions that could alter installation methods and production rates, and we determined that digging conditions were not ideal because of subsurface conditions and severe slopes.
Once existing conditions had been noted, our team began to estimate the project. We dissected the entire pipeline into three different sections. The first section began at the intake and would run through the heavily vegetated areas; we assumed slower production rates for this section due to the difficult material staging and transportation. The next section would involve less clearing and grubbing efforts and assumes we can trim trees and edge up the ROW for access, resulting in faster production rates. The third segment of the pipeline would run along Bee Caves Parkway and would require essentially no clearing and grubbing, so production rates should be fast. In addition to the two alternatives that we were provided, we've tried to find a third alternative that's similar to first but would require less grubbing and could yield faster productions, thereby reducing cost.
We also discussed a directional drill from the water plant site to the intake site. We would be pushing the limits of directional drilling because this would be one of the longest single drills installed in the state, and there's an elevation difference of approximately 450 feet between the top and bottom of the drill. This option would have less of an impact on the surrounding environment, but it comes with a larger investment.
We are currently waiting for the utility agency and consulting engineer's decision to determine the next step in the process.