NPDES Post Const. water quality 1

[wds1]

What methods are other engineers using for stormwater POST contruction water quality for 1 to 5 Ac sites. It seems that Extended Detention is the simpliest to adapt to our existing methods of detention. It requires 1" dia. orifices(metering water for 48 hrs.)which need to be protected by riprap. Most of the other methods require permanent pools and wetlands. I don't think they are going to go well with owners.

 

[cvg]

most municipalities here (Phoenix metropolitan area) require permanent on-site retention of the 100-year, 2-hour storm. This reduces flood runoff, captures water which helps to recharge aquifers and generally functions quite well for NPDES. This does reduce the cost for storm drain pipes which owners would likely have to construct. It also works quite well to provide buffer, landscape and open space areas

 

[TerryScan]

Maryland and Delaware have quality requirements in their stormwater regulations.

http://www.mde.state.md.us/Programs/WaterPrograms/SedimentandStormwater/stormwater_design/index.asp

http://www.dnrec.state.de.us/DNREC2000/Divisions/Soil/Stormwater/Regs/ssregs11.htm

Maryland's regs were recently updated. Delaware has published a draft of new regs.

http://www.dnrec.state.de.us/DNREC2000/Divisions/Soil/Stormwater/Regs/regs2001.pdf

 

[cemorway]

There is alot of diiferent ways to deal with stormwater in use depending on what the primary concern is. Water quality is quickly gaining on, if not exceeding concerns of peak discharge control. Nearly all methods will assist with both, and their is a lot of information available online through state agencies (such as NCDENR). If the concern is quality, the use of grassed swales (instead of piped conveyance) to whatever additonal control you are using can be visually unoffensive while providing additonal filtration. Wetlands or ponds work well in some setting (mosquitos may be a problem but features may be incorporated to assist with their control). Depending on your soils, infiltration basins or bioretention areas may be your best bet without having permanent standing water (if designed correctly). Then their are the structures that can assist with water quality, but not peak runoff control.

 

[bltseattle]

Approaches vary by jurisdiction. In Western WA the typical water quality treatment practices are biofiltration swales, wet ponds/vaults (permanent pools sized for a water quality storm), media filtration (e.g. sand filters), and infiltration when soils allow.

 

[LHA]

I agree with blt, it depends where you are. PA, USA is more or less mandating infiltration for volume, peak control in traditional ways and water quality by various filtration methods. Extended Detention is offered as an alternative, if the above can't be met, due to site limitations (primarily soils in rural areas, existing conditions in urban areas).

For reference, a draft of our new manual is here:

http://www.dep.state.pa.us/dep/subject/advcoun/stormwater/stormwatercomm.htm

Remember: The Chinese ideogram for “crisis” is comprised of the characters for “danger” and “opportunity.”
-Steve

 

[RCEJD]

In the Southern California area, several County and City publications are available. Not only is on-site detention becoming common place, but bio-swales, DC or Austin Sand Filters, CDS Units, catch basin filters such as fossil filters, etc., are typical. In general, mst jurisdictions are requiring 10 percent of a 50 year event be treated.

 

[ALBUD1962]

You really have to watch with infiltration practices. Alot of emphasis is being placed on groundwater recharge, but if the soils and geology are not right you are causing a problem somewhere else downstream from your site. Your best bet with any infiltration practice is to include an underdrain design.