The infiltration basins were placed underground in March, and excavation began for the retention basins. Upon completion, stormwater will be stored in these retention basins and used for subsurface irrigation of this area.
A base of gravel is spread over the area where the retention chambers will sit. A geotextile fabric material will be laid down, over which a thick waterproof pond liner will be put down. The retention chambers will be placed over these layers.
Towards the left-hand side of the above photo, part of the buried infiltration basins can be seen. The retention basins are visible in the background of the excavated area.
In the above photo, the retention basins are installed and will be buried underground. The next step is to install the Continuous Deflective Separation (CDS) units. A CDS unit is a specially-designed concrete sump unit that separates out sediment, trash, oil, and grease, while it filters the stormwater that is diverted into the retention and infiltration basins.
Once the park’s surface is restored, North East Trees will install a subsurface irrigation system using the water stored in the basins to irrigate parts of the park. Water-thirsty turf grass will be replaced with a drought-tolerant species of buffalo grass, and native trees will be planted throughout the park. This work will start in June of this year and the establishment of the new plant material will continue through December 2011.