Section 250-RICR-150-10-8.30 - Pretreatment - Deep Sump Catch BasinsA. Deep sump catch basins shall not be used in place of an oil grit separator for LUHPPLs that have the potential to generate runoff with high concentrations of oil and grease.B. Feasibility 1. The deep sump catch basin must be designed in a catch basin-to-manhole configuration (not in a catch basin-to-catch basin configuration) to be used as pretreatment for other BMPs. Catch basin-to-catch basin or inlet-to-inlet configurations are acceptable, but they cannot be counted as a pretreatment practice.2. The contributing drainage area to each deep sump catch basin shall not exceed 0.5 acres of impervious cover.C. Design 1. The deep sump shall be a minimum 4 feet below the lowest pipe invert or 4 times the diameter of the outlet pipe, whichever value is greater.2. The inlet grate shall be sized based on the contributing drainage area to ensure that the flow rate does not exceed the capacity of the grate. The grate shall not allow flow rates greater than 3 cubic feet per second for 10-year storm event to enter the sump.3. Inlet grates designed with curb cuts must reach the back of the curb cut to prevent flow bypass.4. Hooded outlets shall be used in high litter land uses. Care shall be taken to avoid damaging and displacing hoods during cleaning.D. Maintenance 1. Inspections shall be performed a minimum of 2 times a year (spring/fall). Units shall be cleaned annually and whenever the depth of sediment is greater than or equal to half the sump depth.2. The inlet grate shall not be welded to the frame so that the sump can be easily inspected and maintained.3. Sufficient maintenance access shall be considered when designing the geometry of deep sump catch basins.250 R.I. Code R. 250-RICR-150-10-8.30
Amended effective 11/13/2018