Challenge

A general contractor was selected by a local utility company to oversee the relocation of an electrical substation. This process required the construction of several large power lines and installation of numerous underground vaults. The project was located 0.25 miles from the coast, so the water table was very shallow near the construction site. The underground work was going to require significant dewatering installations to allow dry subterranean construction. Due to strict environmental regulations, groundwater could not simply be discharged back to the ground. The groundwater removed for dewatering would also require treatment and to be discharged to a local Publicly Owned Treatment Works (POTW). Envent was contracted to provide turnkey dewatering services with dewatering installation, dewatering permitting, mobile water treatment solutions, water discharge permits, and equipment operations/monitoring.

Solution

The groundwater will continuously regenerate according to the characteristics of the soil and the water table. Unfortunately, these properties were poorly defined for this project. If the majority of the soil was dirt, then groundwater would flow easily and quickly (leading to fewer, larger pumps). However, if the majority of the soil was clay, then the groundwater would not flow easily (which requires more, smaller pumps). Soil boring logs were obtained to estimate the height of the water table, which was used to plan the depth of pump installation in dewatering wells. Additionally, the soil boring logs report the general soil characteristics to plan quantity and size of pumps required. Estimated flowrates and practical treatment rates were used to obtain water discharge permits to the local sewer and size the treatment system accordingly.

Benefit

With this flexible, but thoroughly engineered solution, the customer was extremely satisfied with dry subterranean construction conditions. As Envent helped mitigate wet subterranean soil conditions, the general contractor saved tens of thousands of dollars in reduced cost and was able to complete work ahead of schedule. The utility company was furthermore able to complete the project under-budget and ahead-of-schedule.