20080680 Ver 1_Staff Comments_20090126

08-0680 Savannah's Garden - Take 5
AML comments
January 26, 2009
Please ensure that the weir that separates the high and low flows to the stormwater
wetland is correctly designed to direct the runoff from the one-inch storm into the
wetland. The DWQ recommends reconfiguring the inlet such that the Swale
receiving runoff from Drainage Area 4 discharges to the forebay of the
stormwater wetland and the weir is placed on the opposite side of the forebay.
The DWQ believes that this design would more effectively separate the flows and
also would dissipate the energy of the runoff. Please provide the appropriate
details and calculations to support the design you select for the inlet structures.
2. Please show that the all discharges to the wetlands are at a non-erosive velocity of
two feet per second or less during the peak flow from the ten-year storm event.
3. The outlet device must be placed at the center of the micropool to reduce the
chance of its being clogged by vegetation.
4. A seed mix may not be used in the planting plan for a stormwater wetland -
please specify plants or plugs for the herbaceous species.
5. Please provide ALL of the required items associated with the stormwater wetland
planting plan, including:
a. A depiction of the mature sizes and spacings for the plantings,
b. A specification of container sizes for the plantings,
c. The total number of each type of plant needed, and
d. A planting detail.