Infiltration Systems Pretreatment Criteria
> 25% of WQv must be pretreated before entry (> 50% if soil infiltration rate is > 2 inches/hour) using the following (or equivalent):
- sedimentation basin
- stilling basin
- sump pit
Use redundant pretreatment methods
- grass channel
- grass filter strip
- bottom sand layer
- upper sand layer
- washed bank run gravel as aggregate
Notes:
Pretreatment is a critical component of infiltration systems and will have a significant role in the longevity of the practice. Without adequate and redundant pretreatment, infiltration practices can be expected to clog easily and quickly. This and the following slide provide some guidance on recommended pretreatment criteria.