Proposed Storm Water Management System Bioretention Facility

1
Proposed Storm Water Management System
Bioretention Facility 400 Block of Howard St.,
Syracuse, NY Service Learning Project Jillian
OFarrell, Satoshi Hirabayashi Dr. T. Endreny
FEG 340 Engineering Hydrology Hydraulics
Course, 207 Marshall Hall, SUNY College of
Environmental Science and Forestry, Syracuse, NY
13210
Background The City of Syracuse, NY is located at
the northern end of the Onondaga Creek watershed.
The watershed runs south to north from Central
New Yorks Appalachian Plateau to Onondaga Lake
in Syracuse. Syracuse has struggled with
stormwater management for over 100 years. There
is currently a system of stormsewers and combined
storm and sanitary sewers that are designed to
collect water from the impervious urban areas and
discharge to the METRO wastewater treatment
facility before flowing into Onondaga Creek.
During periods of heavy precipitation, combined
sewer overflow (CSO) is discharged directly into
Onondaga Creek causing unacceptable levels of
pollution. This stormwater management system is
both inadequate for the needs of the city and
representative of outdated practices that are not
ecologically sensible. The City of Syracuse is in
need of ecologically based stormwater engineering
which utilizes best management practices (BMP)
and low impact designs (LID). To alleviate the
problems associated with CSO, many sites within
the City of Syracuse should be fitted with LIDs
for stormwater control mechanisms. Though each
site has only a small impact on the total
stormwater problem, the combined effect of
numerous LIDs across the large urban area can
have a very large impact on stormwater management
within the city.
Subject Area The site chosen for this particular
design is a paved parking lot on Howard St.
between Wayne St. and Green St. The parking lot
is approximately 30m by 25m and slopes downward
from the northern to southern corners. Due to the
water flow dynamics and the large area of the
site, it would be most effective to construct two
bioretention devices for the lot. The lot is
divided into two sections one that is 15m by 20m
in the northern corner and one that accounts for
the rest of the lot, with an area of 450m2. This
design focuses on the first section.
BMP LID Alternatives With the site
characteristics and design goals in mind, the
table to the right shows possible BMP options and
shows that a bioretention device will best suit
the goals of the design. The figure to the left
shows the basic elements of LID that were
considered in the decision process. Variations
of bioretention designs that were considered
included creating one retention device for the
lot vs. creating two devices. Variations in the
size, shape, location and content of the devices
were also considered.
http//www.nysgis.state.ny.us/gateway/mg/index.htm
l.
North facing photograph showing lot with existing
drain

• Goals and Constraints
• The overarching goal of this design is to
  minimize the impact of the urban areas of
  Syracuse, NY on Onondaga Creek and thereby on
  Onondaga Lake by controlling the discharge of
  rainwater within the city. The more specific
  goals and constraints of this project are
• Create a stormwater retention device to treat
  point and non-point source runoff.
• Create an aesthetic, environmentally healthy,
  small scale, low cost retention basin.
• The design must conform to the standards of best
  management practices defined by the EPA and be a
  low impact development.
• The device must capture the stormwater volume
  generated by a 24 hour duration, 2 year
  recurrence interval storm event of 6.8cm depth.
• The device under-drain must tie into the existing
  storm sewer or groundwater system.
• The device must pond water for the design event
  to a maximum of 15cm.
• The device should be 5-7 of the drainage area
  and have an area not larger than 16m2.
• The device must infiltrate water every 6 hour
  period to reset the ponding depth.
• The device must have the vertical layers and
  assemblages of microbes and plants outlined by
  the EPA.

www.lowimpactdevelopment.org/school/pictures.html
http//www.metrocouncil.org/environment/Watershed/
BMP/manual.htm
Outcomes
Conclusions
Recommendations
Design is to account for a 24hr, 2year recurrence
interval storm of 6.8cm depth. The NRCS CN method
was used to calculate the runoff depth and
volume, the Green and Ampt Infiltration Model and
Darcys equation were used to estimate the
infiltration depth, the Manning equation was used
to calculate drainpipe diameter.
The bioretention basin will be placed as an
island near the center of the lot as shown in the
figures below. The 2nd device could be placed as
shown in the southern corner where there is
currently a storm drain. The design allows for
minimal loss of parking area and provides an
aesthetically pleasing element to the site. The
bioretention area may be surrounded by a curb
with numerous inlet notches.

• Refer to design report for complete, detailed
  specifications of design.
• Filtration Layers, as shown in Figure 3 below
• The device bottom is to be lined with a sand
  interface layer of 3in thickness.
• The second layer should be 2 to 3ft of coarse
  gravel or sand.
• The PVC underdrain pipe should be 4in in diameter
  and drain toward the existing stormsewer drain.
• The next layer is to be 4in of fine gravel to
  cover the underdrain pipe.
• Above the underdrain and gravel layers there
  should be a layer of filter fabric.
• The next layer is to be 3 to 3.5ft of a planting
  soil mixture. The type of soil that best suites
  the site parameters is loamy sand.
• The top layer of the basin should be a 2 to 3in
  cover of mulch.
• An overflow pipe should be placed at the center
  of the device, running upward through the device
  with an open top at the maximum ponding depth of
  15cm.
• The overflow pipe should be connected at its
  bottom to a separate drainage pipe that leads
  excess water to the
• existing stormsewer system.
• Completely surrounding the basin
• should be a strip of coarse grass
• planted on an inward sloping bank
• to even flow into the basin and
• collect large debris.
• The inner area of the basin should
• be planted with native plants that

Drainage Area A300m2 Bioretentio
n Area Abio 15m2, Lbio8m,
Wbio1.875m Slope
Y0.02 Manning Roughness 0.05 0.15 Max.
Hydraulic Flow Lmax35m NRCS Curve Number
CN98 Runoff Depth
Pe6.216cm Runoff Volume
VR18.647m3 Runoff Rate
RO2.15810-4m3s-1 Max. Ponding Depth
dmax15cm Max. Accumulation in Device
Vbio2.25m3 Ponding Reset Time
6hrs. Infiltration Rate
IR1.21810-4 m3s-1 Under-Drain Diameter
D4in Depth of Under-Drain d2m
Wayne St.
http//www.wbdg.org/design/lidtech.php
Howard St.
http//www.co.stafford.va.us/code/Stormwater_Manag
ement/Low_Impact_Development_Demonstration_Project
.shtml

• References
• USEPA Bioretention Facility Fact Sheet
  http//www.epa.gov/OW-OWM.html/mtb/biortn.pdf
• NYS GIS Orthoimagery http//www.nysgis.state.ny.u
  s/gateway/mg/index.html.
• International Stormwater Best Management
  Practices (BMP) Database http//www.bmpdatabase.o
  rg/
• Metro Council Urban Small Sites BMP Manual
  http//www.metrocouncil.org/environment/Watershed/
  BMP/manual.htm
• Bioretention for Infiltration (1004) Wisconsin
  Department of Natural Resources Conservation
  Practice Standard http//www.dnr.state.wi.us/org/
  water/wm/nps/stormwater/techstds.htmPost

Some native plants that would be suitable to
plant on the site are shown at right. (images
from USDA NRCS website)
Pussy Willow Salix discolor
Swamp Azalea Rhododendron viscosum
Prairie Cordgrass Spartina pectinata