Problem: The Lakes Region Sanitary District South Trunk Sewer provides sanitary sewer service to over 2,500 acres in the Village of Volo and unincorporated Lake County. The ultimate design population for the system is approximately 26,000 population equivalents. A major consideration in the project design was accommodating both low flows at the onset of development and ultimate design flows within the same infrastructure.
Solution: The project consisted of construction of two regional wastewater pumping stations, 5,700 feet of gravity sewer and 30,550 feet of forcemain. Key design features to accommodate the range in flows included dual, parallel forcemains, provisions for forcemain cleaning, future conversion from duplex to triplex pump stations, appropriate pump selection, and the use of variable frequency drives. Construction methods included open cut construction, cased horizontal augered borings and horizontal directional drilling.
A major component of the project was to provide sanitary sewer service to two critical service areas in a short period of time. . The service areas included a new school at the north end of the system and the developing community of Volo at the south end. In order to ensure the delivery of sanitary service on time, the following tactics were implemented:
1.) The project was split into two phases, a North Section and a South Section
2.) Controls and generator were pre-purchased by the owner and installed by the general contractor
3.) Both equipment purchase and construction contracts included provisions for incentives for early completion and penalties for delays.
Both projects were complete and ready for use well before the required service date.
To aid in operation and maintenance of the long forcemain sections, state of the art “pigging stations” were designed and constructed at each of the lift station sites. The concept of “pigging” of pressurized piping systems originated in the petroleum industry and has since been applied to watermains and sanitary sewer forcemains.This project is the first in Illinois to include the design and construction of a permanent structure utilized to “pig” a dual forcemain system on a periodic basis for maintenance.
The pig launching structures included the pig launcher and a complex piping/valving arrangement (consisting of plug and gate valves) to allow for pigging of either of the dual forcemains from a single pig launcher.