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Summary
The Homestead Detention Pond Low Impact Retrofit Project involved converting a traditional low flow bubble up detention pond system with a low impact surface and subsurface infiltration/evaporation system.
Project Detail
The Homestead Detention pond was not working resulting in flooding downstream. The flood control system was a low flow bubble up design consisting of four sub-basins connecting at a single outfall. The single point sub-basin collection system was not optimum for conveyance and its existing low flow design conveyed the majority of urban pollution downstream. To maximize the conveyance for flood control purpose and conform to UPDES requirement 4.2.6.9 the City modified the pond with four independent sub-basin inlets discharging to shallow drywells, horizontal subsurface infiltration pipes and surface vegetation. This not only improved conveyance rates by distributing the inlet points to the pond but also distributed the entire basins urban pollution load to shallow subsurface systems and surface vegetation.
However, some urban pollution is discharged directly to drywells with out pretreatment increasing the risk to subsurface contamination. This requires more attention spills, illegal dumping and will be more expensive to mitigate than a surface low impact pretreatment system would require.
Project was designed and built by Stormwater Division.
2019 Detention Pond Low Impact Retrofit Project Plans
2019 Riverton City Hall Entry Improvements
Summary
The City Hall entry improvements involved draining the new impervious surfaces to shallow drywells.
Project Detail
The entry improvements consisted of 17,000 SF of impervious surface of driveway, parking and pedestrian walkways. The increased impervious surface is managed by 3 shallow drywells.
Unfortunately, urban pollution is discharged directly to drywells with out pretreatment increasing the risk to subsurface contamination. This requires more attention spills, vehicle leaks and is more expensive to mitigate than surface low impact pretreatment system would require.
Project was designed by Engineering Division
2019 Riverton City Hall Entry Improvements Project Plans