Traditional stormwater criteria require both improving the quality and managing the quantity of runoff. One of the best practices is to incorporate pretreatment, detention and treatment into an integrated system. This approach can meet total daily maximum load requirements by providing a high level of pollutant removal and preventing erosion damage from peak flows. Many areas may require only some of these processes while some areas may require all of them. Here are eight benefits of using this three-tiered approach to stormwater treatment:

Pretreat with a hydrodynamic separator or screening device to…
1. Remove trash, debris and solids from runoff, even at high flows
2. Reduce downstream loading of oil and other pollutants to prevent clogging/ reduce system maintenance costs

Use underground detention/infiltration to store and discharge stormwater over time…
3. Downstream of the separation unit to slow the rate of runoff to match predevelopment flow rates
4. Upstream of filtration to reduce flow rates thus reducing the size of the filtration system
5. To maximize property usage by eliminating above ground systems
6. To provide maximum storage capacity in available footprint/profile

Use underground filtration upstream to…
7. Remove the most challenging target pollutants – including fine solids, soluble metals, total phosphorus, oil and grease, organics and nutrients
8. Save land space, allow denser development and reduce sprawl