ACEC

Tollway
US 34 Widening and Reconstruction

Firm:GRAEF


Other Consultants:Ames Engineering, Testing Services Corp., D Construction


Owner:Illinois Department of Transportation


Description:IDOT needed to widen and reconstruct a stretch of US 34 in Yorkville, Illinois to alleviate traffic congestion, provide improved pedestrian accommodations, and improve drainage.


Due to the proximity of US 34 to the Fox River, regulatory agencies would not permit a direct dis-charge of storm water to the river. Instead, certain areas of the project required that drainage systems be devised that would allow water to seep into the ground and travel along sand seams to the river.


In order to meet the drainage requirements, GRAEF developed various alternate drainage schemes that did not provide a direct outlet to the river. These included infiltration trenches, 3-sided inverted “U” structures, open bottom manholes, and infiltration ponds. These approaches were used depending on the right-of-way constraints, local resident concerns, and infiltration rates of the soil. Percolation tests were also completed by Testing Service Corporation to ascertain the ability of the site soils to infiltrate groundwater. In addition, wells were placed and monitored for over a year prior to construction. This testing and monitoring permitted the designers to determine the infiltration footprint that would be needed to accommodate various storm events and select the most appropriate drainage method for different locations within the project.


Although each of these drainage approaches have been used previously, the GRAEF team had to site-adapt the various approaches to meet localized conditions. Iterations to the designs were completed in order to develop the optimum solutions given the project constraints.


The most unique aspects of the drainage design were the infiltration trenches and ponds that were developed for the project. Several variables including rainfall data, soil conditions, percolation rates, and right-of-way constraints needed to be accounted for in the design. The infiltration trenches used large diameter perforated high density polyethylene (HDPE) pipe, pervious stone backfill, filter fabric, and an infiltration stratum below to infiltrate the stormwater into the groundwater.


During construction, difficulties were encountered installing the fabric wrapped aggregate for the infiltration sewer. Wrapping the trench backfill with fabric is an unusual condition not commonly used while constructing storm sewer. The contractor indicated they had not experienced this before and did not know the best way to address the installation within a trench shoring box. The solution was a roll of fabric mounted on the trench box. The contractor, D Construction, would excavate, roll out a length of fabric sufficient to envelope the trench backfill, and drape the fabric around the sides and bottom of the excavation. After placing pipe and trench backfill, the fabric was wrapped over the excavation to complete the envelope and the trench box could be advanced in the customary manner.


Conventional stormwater design for a highway project typically includes concrete storm sewer, concrete culverts, concrete structures, and detention ponds. This project used infiltration trenches, infiltration ponds, and perforated HDPE pipe, as well as conventional design.






Illinois Department of Transportation

        WSP Logo