Water Quality
Management Program
Staff Training
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Consultants, Inc.
Agenda
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Why is this change necessary?
Program rationale
Describe new BMPs
Plans review process
Operation and Maintenance Plan
Design examples
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NPDES Phase 2 regulations:
• 6 Minimum Control Measures
• Post construction storm water quality
treatment
• “…treat storm water to the maximum
extent practicable…”
• All new developments and
redevelopments disturbing 1+ acres
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Steps Taken to Date:
•
•
•
•
•
Ordinance with post construction language
BMP storm water stakeholder group
BMP Manual revised
Ordinance revised
Developed plan review and permitting
processes
• Training
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Schedule
• Effective date = March 31
• If plan has been platted and has approved
SWMP, no additional storm water quality
treatment required.
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About the program…
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Program rationale
• Step 1: Define “Maximum Extent
Practicable” (MEP) for Bowling Green.
• Step 2: Establish how much treatment is
enough.
• Step 3: Develop a “doable” program.
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How the City Defines MEP:
 Identify pollutant of concern (303d lists, TMDLs)
 Establish pollutant load reduction goal
– Based upon accepted research, other communities
– No need to reinvent the wheel…
 Develop design features and practices that work
for the City
– Treatment volume based on impervious surfaces
– Consider local limitations (karst, groundwater table)
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Pollutant of Concern
• Sediment or total suspended solids (TSS)
• Available BMP research
• Many other programs using TSS as
pollutant of concern
• KYR10000 – references 80% TSS
reduction
• Sediment is no. 1 pollutant in nation
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Impervious Cover
• TSS loading is higher from impervious
cover
• Impervious cover…
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Sidewalks
Roads
Driveways
Parking
Buildings
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Establish treatment goals/limits
• Water Quality Treatment required for sites that disturb 1 ac or
more AND add 10,000ft2 or more new impervious surfaces
• WQv = [(P Rv)(A)]/12
• Where,
• WQv is the water quality treatment volume (ac-ft)
• P is the average rainfall in inches, (in the case of Bowling Green, is
1.1 inches);
• Rv is the volumetric runoff coefficient, which is:
• Rv = 0.05 + 0.009(I), where I is the percent impervious cover;
• and A is the area in acres
• Set treatment goal based upon pollutant of concern…
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A “Doable” Program
• Presumptive program:
– IF you design as described in BMP Manual
– IF you install per the approved plans
–
AND
– IF you maintain the BMP per the Operation &
Maintenance Plan
–
THEN
– You are in compliance.
• Discharge influent/effluent testing not required
(for now…)
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Best Management Practices
• Mitigate storm water
quality and quantity
damages from
development
Wetlands
Wet Ponds
Dry Ponds
Bioretention
areas
Water
quality
swales
Infiltration
trench
Sand filter
Water
quality
units
Manufactured
devices
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Ponds
• Dry ponds
– Outlet
structure
– Dry storage
area
– 60% TSS
reduction
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Ponds
• Wet ponds
– Outlet
structure
– Permanent
pool
– 80% TSS
reduction
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Ponds
• Variations
– Micropool
– Extended
detention
– Multiple ponds
– Pocket ponds
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Wetlands
• Outlet structure
• Shallow wet
treatment area
• Upland dry storage
• Plants are key
• Length of flow
(residence time) key
• 75% TSS reduction
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Bioretention areas
• Outlet structure
– Small storm & large
storms
• Dry treatment area
– Depressed planting
area
– Specific soils
– Under drain
• 80% TSS reduction
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Open Channel Systems
• Simple outlet
system
• Treatment area
• Dry
– good in most all land
use applications
– Underdrain system
• Wet
– Not well accepted in
residential
– Long wetland
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Sand filters
• Many variations
• Best suited for
non-residential
• Typically
underground
• Must receive
drainage from only
impervious
surfaces
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Infiltration trenches
• Limited application
due to karst
topography
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Manufactured BMPs
• Treatment mechanisms different
from non-manufactured BMPs
• Must provide 3rd party testing to
verify pollutant removal to get
approved for use
• Nashville has similar program – will
use Nashville’s list of approved
BMPs and reduction capabilities
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Summary table
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WQMPs
• Trigger: 1 ac or more disturbance and
10,000 ft2 new impervious surfaces
– Or part of a larger common plan of
development
• DPW is point of contact for info on WQMP
– P&Z will have checklists and general info
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Conservation Subdivision
• WQMP =
– Clearly defined clearing limits
– Total impervious surfaces for development
cannot exceed 15%
– Minimum lot sizes – 1 acre
– Disconnected roof drains
– Stabilized sinkhole basins
• No additional WQ treatment required
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Hot Spot Landuses
•
Pretreatment required for following landuses:
1.
2.
3.
4.
•
Automotive Fueling Facilities
Automotive Repair Facilities
Restaurants with grease collection and disposal
Other landuses as determined to have a high
potential of pollutant discharge into the MS4 as
determined by the City Engineer
Typically, oil grease separators, hydrodynamic
separators, etc.
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Asbuilt Certification
• Need to verify
– That BMP was installed per
approved plans
– That WQv treatment goals
being met
• Engineer and surveyor
• Asbuilt must be approved
before:
– Bonds released (S/D)
– CO issued (non-S/D)
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Maintenance
• City to maintain BMPs in
– residential areas
– on public ROWs
• Landowner to maintain all other BMPs
• All BMPs
– O&M Plan
– Routine inspections
– Annual inspection certification
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O&M Plan
• Includes the following:
– BMP Maintenance Agreement
• Privately owned BMPs only
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–
–
–
O&M Plan
Lashlee Landings
- Agreement
- Location map
- Schematics
- Inspection checklists
BMP location map
BMP schematics
BMP maintenance and inspection templates
Annual BMP report template
• Recorded with the deed
• Privately owned BMPs only
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BMP Location Map
Drainage
Easement
Bioretention #1
Bioretention #2
Access
Easement
Detention
Pond
Drainage
Easement
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BMP Schematics
Redbud, 10’ O.C
Daylilies, 2’ O.C.
18”
storage
2.5’ planting
media
Geotextile
fabric
6” #57 stone
4” perforated
plastic pipe
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BMP Schematics
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BMP Inspection Checklists
Storm Water Bioretention Area
Inspection Checklist for BMP Owners
Maintenance Item
Maintenance
needed?
(Yes/No)
Inspected?
(Yes/No)
Site name: ___________________________________________________________________________________
BMP Number: _________________________________________________________________________________
Owner Change since last inspection? Y N
Owner Name__________________________________________________________________________________
Address ______________________________________________________________________________________
Phone Number ___________________________Location: ____________________________________________
Inspection Date: ______________________________________ Time: __________________________________
Inspector: ___________________________________________________________________________________
Weather Conditions:____________________________________________________________________________
Was flow observed: If so, what was the appearance of the water (i.e. color, sheen, estimated flow rate, etc.)?
____________________________________________________________________________________________
Comments
Treatment area (Inspect after major storm events)
1. Evidence of drainage (Is water ponding
less than 24 hrs after rain event?)
2. Signs of erosion noted (in contributing
watershed or in bioretention area?)
3. Mulch condition – thin or decomposing?
4. Sediment deposits noted in treatment
area?
5. Vegetation condition
6. Overflow spillway in good condition?
7. Other (describe)
Completed?
Y/N
Maintenance Action Needed
Date
Due
Note: If any inspection items were checked “yes” for maintenance needed, list maintenance actions and dates
completed below.
Civil & Environmental
Inspector signature: ____________________________________________________________________________
Consultants,
City of Bowling Green
Storm Water Contact Information: 270-393-3628
Inc.
Residential Example:
Lashlee Landing
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Site Data - 51 Single
Family Lots
Area = 38 ac.
Impervious Area = 13.8 ac 36%
3 ac in roadway and driveways,
10.8 ac in roof tops
WQv=[(P Rv)(A)]/12
Rv = 0.05 + 0.009(I)
WQv = [1.1*(0.05+0.009*36)*38]/12
= 1.30 ac-ft
Scenario 1:
Wet pond = 80% TSS
DA1, DA2, DA3 routed to pond
 (TSS A  TSS A  ...  TSS
 ( A  A  ...  A )
Single Drainage Area
1
%TSS 
n
1 1
1
n
2
1
2
2
n
n
An )
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Site Data - 51 Single
Family Lots
Area = 38 ac.
Impervious Area = 13.8 ac 36%
3 ac in roadway and driveways,
10.8 ac in roof tops
2 drainage basins
Each has to treat WQv; weighted
TSS reduction goal
Drainage Area (DA) 1
Area = 7.6 ac.
Imp Area = 2.25 ac; I = 2.25/7.6 = 30.0%
Drainage Area (DA) 2
Area = 30.4 ac.
Imp Area = 11.55 ac; I = 11.55/30.4 = 38.0%
WQv=[(P Rv)(A)]/12
Rv = 0.05 + 0.009(I)
DA1
Rv = 0.05 + 0.009(30) = 0.32
WQv = [(1.1*0.32)*7.6]/12
= 0.22 ac-ft
DA2
Rv = 0.05+0.009(38) = 0.39
WQv = [(1.1*0.39)*30.4]/12
=1.09 ac-ft
Multiple Drainage Areas
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DA1
Rv = 0.05 + 0.009(30) = 0.32
WQv = [(1.1*0.32)*7.6]/12
= 0.22 ac-ft
- 2 Dry WQ Swales
- provides 0.11 ac-ft of WQv in each
- Dry WQ Swales = 90% TSS
reduction
DA2
Rv = 0.05+0.009(38) = 0.39
WQv = [(1.1*0.39)*30.4]/12
=1.09 ac-ft
- Wet pond
- provides 1.09 ac-ft of WQv
- TSS reduction = 80%
%TSS = (7.6*90)+(30.4*80)/38ac
= 82% TSS
Multiple Drainage Areas
Therefore, site okay
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Treatment Train
• When one BMP discharges into another
• Discharge from upstream BMP will be “clean” so
downstream BMP TSS reduction will be less effective
TSStrain  A  B 
Flow
Bioretention
80% TSS
( A  B)
100
Flow
Dry Detention
60% TSS
TSS reduction = 80+60 – (80x60)/100 = 92%
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DA2
Scenario 2:
DA1 =
Dry detention = 60% TSS
Bioretention
areas to dry
detention
DA1
DA1 = 10ac @60% TSS
DA2 = 15ac @80% TSS then
60% (treatment train)
DA3 = 13 ac @90% TSS
DA2 %TSS reduction
= 80+60 – (80x60)/100 = 92%
Dry
Swales
TSStotal = ([10ac x 60] + [15ac x 92] + [13ac x 90]) / 38
= 82.8% TSS
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Commercial Example:
Creekwood Village
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Creekwood Village S/D
• Multi-family
• Dry regional detention
facility
• Goal - Regional WQMP:
– Provide regional WQ
BMPs
– Establish builtout
imperviousness per lot
• Problem:
– Assume 15 acres, 40
lots w/80%
imperviousness per lot,
1500 linear ft of
roadway.
– What is WQv?
– What BMPs might
work?
– Where?
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Lots 6 and 7
• Regional WQMP
– Review against
restrictions
– If above restrictions,
require additional on
lot treatment
• Individual WQMP
– Develop WQMPs as
unit (lots 6-7) or
separately
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Problem:
Lot 7 – 0.67 ac total,
25% impervious cover
Drainage
Easement
Lot 6 – 1.1 ac total,
23% impervious cover
Bioretention #1
Problem:
What is the WQv?
Does this WQMP meet
the TSS reduction
goal if developed as
one WQMP?
Bioretention #2
Access
Easement
Dry Pond
Drainage
Easement
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Questions and Discussion
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