3. Drywell Design and Construction

  • The standard drywell is the Maxwell IV or equal. The standard drywell system shall include an Interceptor Well upstream of any drywell(s).
  • Drywells will be offset a nominal distance of 20 feet from any surface inlet. When a drywell is constructed in conjunction with a surface inlet, the diameter of the connecting pipe from the interceptor well to the drywell shall be a maximum of 4 inches.
  • Drywells constructed in a landscaped area shall have a rim elevation 2.0 inches above the finished elevation. Design of drywells in detention basins will not be allowed. Drywells are intended for nuisance water disposal, not storm water disposal.
  • Drywells will remain sealed until all paving or landscaping is completed (or until new grass is stable) to prevent unnecessary sediment from being deposited in the drywell.
  • Drywells will have a minimum settling basin depth of 25 feet, a 4 foot inside diameter, 30 inch bolt down grates and 6 inch drainage components. Drywell dimensions may be varied, subject to the approval of the City Engineer, if the settling volume is 250 cubic feet or greater.
  • Drywells will be spaced a minimum of 75 feet center to center.
  • The minimum distance between a drywell and a waterwell shall be 300 feet.
  • Drywell design shall be in accordance with City Stds. D-1.1 and D-1.2

4. Drywell Performance and Inspection

a. A Soils Engineer or an Engineering Geologist shall perform percolation tests on each drywell installed to verify its capability to dispose of the anticipated inflows.

V-21