Volume 2-05, Chapter 3 - City of Wichita

Section 3.2.2 - Extended Dry Detention Pond
• Riprap, plunge pools or pads, or other energy dissipators are to be placed at the end of
the principal spillway outlet to prevent scouring and erosion. If the basin discharges to a
channel with dry weather flow, care should be taken to minimize tree clearing along the
downstream channel, and to reestablish a vegetated riparian zone in the shortest possible
distance.
• A concrete emergency spillway is to be included in the stormwater pond design to safely
pass the extreme flood flow. The spillway prevents pond water levels from overtopping
the embankment and causing structural damage. The emergency spillway must be
located so that downstream structures will not be impacted by spillway discharges.
• A minimum of 1 foot of freeboard must be provided, measured from the top of the water
surface elevation for the 100 year flood event, to the lowest point of the dam embankment
not counting the emergency spillway. The 100-year flood elevation for emergency spillway
design is based on the elevation required to pass the 100-year flow with no discharge
through the principal spillway.
• Please refer to “Stormwater Pond”, Section 3.2.1, for additional requirements applicable to
all surface detention ponds.
• The use of the simplified method (Chapter 4) for configuring the CP v orifice is the same as
for wet extended detention ponds (Section 3.2.1.).
Maintenance Access
• The local jurisdiction may require that the pond be placed in a reserve and/or
establishment of a drainage easement to the pond, which is accessible from a public road
or other accessible easement. When required, the drainage easement should be at least
20 feet wide, provide a minimum traversable width of 15 feet, have a maximum slope of no
more than 10%, and be appropriately stabilized to withstand maintenance equipment and
vehicles.
• When required, reserves and/or drainage easements must extend to the forebay, safety
bench, riser, and outlet and, to the extent feasible, be designed to allow vehicles to turn
around.
• Access to the riser is to be provided by lockable manhole covers, and manhole steps
within easy reach of valves and other controls.
3.2.2.4 Inspection and Maintenance Requirements
Regular inspection and maintenance is critical to the effective operation of stormwater
management facilities. An operation and maintenance plan is required and shall include:
1. “Covenants for Permanent Maintenance of Stormwater Management Facilities” (also
called the “Maintenance Covenants”).
2. “Inspection Checklist and Maintenance Guidance” for each type of stormwater facility that
is located on the property. Templates for each stormwater management facility can be
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Volume 2, Technical Guidance