Runoff passes through either vegetation in the channel, subsoil matrix and/or is infiltrated into the underlying soils.
Site assessment for buried infrastructure and other utilities must be undertaken.
The public likely does not recognize this practice as it is relatively benign in appearance.
Moderate.
This practice is typically funded by developers during construction.
Costs estimated as $ per impervious acre treated.
Cost Estimates | EPA | King & Hagan | Average |
Initial | $762 | $6,500 | $3,631 |
Annual | $507 | $128 | $317.50 |
Lifespan (yrs) | 20 | 20 | 20 |
Annualized | $545.10 | $453 | $499.05 |
Notes: King & Hagan figures are expressed in units of “impervious acres treated”. This provides a unit of comparison that is more uniform than “acres treated,” which assumes a proportion of impervious to pervious coverage. EPA figures have been converted.
Total Nitrogen removed per impervious acre treated per year
Low 2.67 lbs. |
Medium 3.06 lbs. |
High 6.28 lbs. |
Cost per pound removed = between $79 and $187
Total Phosphorous removed per impervious acre treated per year
Low 0.10 lbs. |
Medium 0.17 lbs. |
High 0.49 lbs. |
Cost per pound removed = between $1,024 and $5,045
Total Suspended Solids removed per impervious acre treated per year
Low 44 lbs. |
Medium 84 lbs. |
High 534 lbs. |
Cost per pound removed = between $0.93 and $11.24
These grasses are sod-forming and can withstand frequent inundation and are ideal for the swale or grass channel environment. Most are salt-tolerant, as well.
If this BMP is likely to receive excessive amounts of deicing salt, salt tolerant species should be used.
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