Housing Community Design 

This example will demonstrate the differences between conventional and LID stormwater management approaches for a typical DoD housing community in a coastal area.  The design objectives are to maintain the peak runoff rate for a Type II NRCS 2-year 24-hour storm event and provide water quality control for the development.

Several LID site design strategies will be employed to reduce the CN for the proposed condition.  A lower CN value will be obtained by:  

§         Reducing impervious cover

§         Disconnecting impervious areas

§         Reducing the grading footprint to retain more wooded area

§         Restoring the infiltration capacity of disturbed and compacted soils

This case study has shown how LID can be incorporated into the design of a residential housing development.  The use of LID practices has eliminated the need for a traditional stormwater detention pond, thereby reducing the disturbance to existing forested area.  The retention of this forested buffer will in turn reduce impacts to the wetland and receiving waters.  The need for piped stormwater conveyances has been eliminated.  The LID approach has the added benefit of improving the aesthetics of the development and can provide opportunities for community involvement in the protection and maintenance of the local environment. 

Office Complex Retrofit 

Four types of LID components were selected: bioretention, permeable pavers, tree box filters, and a vegetated roof.  Because of the poor infiltration capacity of the soil, these features will not be capable of infiltrating stormwater into the ground.  Instead, they will be equipped with underdrains and used to control water quality and provide detention storage.  Site drainage areas were delineated, and LID features were located in places both appropriate to the technology and to the runoff patterns and volumes. 

Projected Load Reduction After LID Retrofit 

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