Water Quality Management Program Staff Training

1
Water Quality Management ProgramStaff Training
2
Agenda

• Why is this change necessary?
• Program rationale
• Describe new BMPs
• Plans review process
• Operation and Maintenance Plan
• Design examples

3
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

4
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

5
Schedule

• Effective date March 31
• If plan has been platted and has approved SWMP,
  no additional storm water quality treatment
  required.

6
About the program
7
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.

8
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)

9
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

10
Impervious Cover

• TSS loading is higher from impervious cover
• Impervious cover

11
Sidewalks
Roads
Parking
Driveways
Buildings
12
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

13
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)

14
Best Management Practices

• Mitigate storm water quality and quantity damages
  from development

15
Ponds

• Dry ponds
• Outlet structure
• Dry storage area
• 60 TSS reduction

16
Ponds

• Wet ponds
• Outlet structure
• Permanent pool
• 80 TSS reduction

17
Ponds

• Variations
• Micropool
• Extended detention
• Multiple ponds
• Pocket ponds

18
Wetlands

• Outlet structure
• Shallow wet treatment area
• Upland dry storage
• Plants are key
• Length of flow (residence time) key
• 75 TSS reduction

19
(No Transcript)
20
(No Transcript)
21
Bioretention areas

• Outlet structure
• Small storm large storms
• Dry treatment area
• Depressed planting area
• Specific soils
• Under drain
• 80 TSS reduction

22
(No Transcript)
23
(No Transcript)
24
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

25
(No Transcript)
26
Sand filters

• Many variations
• Best suited for non-residential
• Typically underground
• Must receive drainage from only impervious
  surfaces

27
Infiltration trenches

• Limited application due to karst topography

28
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
  Nashvilles list of approved BMPs and reduction
  capabilities

29
Summary table
30
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
• PZ will have checklists and general info

31
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

32
Hot Spot Landuses

• Pretreatment required for following landuses
• 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.

33
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)

34
Maintenance

• City to maintain BMPs in
• residential areas
• on public ROWs
• Landowner to maintain all other BMPs
• All BMPs
• OM Plan
• Routine inspections
• Annual inspection certification

35
OM Plan
OM Plan Lashlee Landings - Agreement - Location
map - Schematics - Inspection checklists

• Includes the following
• BMP Maintenance Agreement
• Privately owned BMPs only
• BMP location map
• BMP schematics
• BMP maintenance and inspection templates
• Annual BMP report template
• Recorded with the deed
• Privately owned BMPs only

36
BMP Location Map
37
BMP Schematics
38
BMP Schematics
39
BMP Inspection Checklists
40
Residential Example Lashlee Landing
41
Single Drainage Area
42
Multiple Drainage Areas
Rv 0.050.009(38) 0.39 WQv
(1.10.39)30.4/12 1.09 ac-ft
43
DA1 Rv 0.05 0.009(30) 0.32 WQv
(1.10.32)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
0.050.009(38) 0.39 WQv (1.10.39)30.4/12
1.09 ac-ft - Wet pond - provides 1.09
ac-ft of WQv - TSS reduction 80 TSS
(7.690)(30.480)/38ac 82
TSS Therefore, site okay
Multiple Drainage Areas
44
Treatment Train

• When one BMP discharges into another
• Discharge from upstream BMP will be clean so
  downstream BMP TSS reduction will be less
  effective

TSS reduction 8060 (80x60)/100 92
45
Scenario 2 DA1 Dry detention 60 TSS DA1
10ac _at_60 TSS DA2 15ac _at_80 TSS then 60
(treatment train) DA3 13 ac _at_90 TSS
46
Commercial ExampleCreekwood Village
47
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?

48
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

49
Problem Lot 7 0.67 ac total, 25 impervious
cover Lot 6 1.1 ac total, 23 impervious
cover Problem What is the WQv? Does this WQMP
meet the TSS reduction goal if developed as one
WQMP?
50
Questions and Discussion