Dry Well System
The design of the dry well system consists of a treatment train of three components: a vegetated pre-treatment feature, sedimentation well, and the dry well itself, as depicted in the diagram below. The vegetated pre-treatment feature will store and filter stormwater for a minimum of 7-minutes and will reduce peak discharge rates and total runoff by using soil amendments to increase infiltration. The second stage of pre-treatment, the sedimentation well, will trap and filter additional sediment before runoff is discharged into the dry well. The dry well itself has been designed to capture any remaining suspended solids by including both sand and gravel layers at the top of the well. While the pervious layers will facilitate a high infiltration rate, the clay layer will cause stormwater to move horizontally to obtain further treatment of potential contaminants and will function as a final step of attenuation.
The project's dry well system to the left is composed of a (left to right) vegetated pre-treatment feature, sedimentation well and a dry well.
Monitoring Well Network
At each site three groundwater monitoring wells will be constructed: one up-gradient and two down-gradient of the dry well. The upgradient well will provide information on the baseline water quality while the two downgradient wells will assess the affects, if any, of the dry well on downgradient groundwater quality. In addition, one downgradient vadose zone well will be constructed about 10 feet from the dry well. The vadose zone well will aide in tracing the movement of contaminants that might pass through the dry well.
The figures below show the layout of the dry well and monitoring networks at the Strawberry Creek Water Quality Basin and the City’s Corporation Yard.