City of Bowling Green

Implementation of MCM 5

Post Construction

Matt Powell

Agenda

History -Regulatory Background Goals Program Development Documentation New BMPs

PROGRAM DEVELOPMENT

Bowling Green’s SW Goals

1. Improve the quality of Bowling Green and Warren County’s water resources by: Implementing minimum control measures Providing education to citizens

2. Provide protection of the short-term and long-term public health, safety, and general welfare by: Protecting, and preserving storm water quality and

fish and wildlife habitat within Bowling Green. Protecting those downstream from stormwater quality

impairment.

Defining the Program

Determine Pollutant of Concern (POC) Establish Pollutant Load Reduction Develop design requirements that

encourage green infrastructure Provide a selection of appropriate

BMPs

Maximum Extent Practicable

To what degree must we implement this minimum control measure and achieve both compliance and unhindered growth and development?

Establishment of a second trigger; 10,000ft2

Hot Spot Landuses

Pretreatment required for following landuses:

1. Automotive Fueling Facilities

2. Automotive Repair Facilities

3. Restaurants with grease collection and disposal

4. 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.

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

Sediment or total suspended solids (TSS) Available BMP research Many other programs using TSS as pollutant of

concern Old KYR100000– references 80% TSS

reduction Indicator pollutant EPA has stated sediment is no. 1 reason for

stream impairment

Pollutant of Concern

The Presumptive Program

The design is as described in BMP Manual

+

The installation is per the approved plans

+The BMP is maintained per the Operation &

Maintenance Plan

=

Compliance.

No Performance testing for preapproved BMPs

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

Never Again

Effective date = April 1 2008 If plan has been platted and has approved

SWMP, no additional storm water quality treatment required.(The Grandfather Clause)

DOCUMENTATION

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)

O&M Plan

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

O&M PlanThe Landings

- Agreement- Location map- Schematics

- Inspection checklists

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

A Tale of 2 Methods

Volume Based BMPs Calculation 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

Manufactured BMPs

Treatment mechanisms different from non-manufactured BMPs

Must provide 3rd party testing to verify pollutant removal to get approved for use (TARP, NJCAT)

Nashville’s list of approved BMPs and reduction capabilities is automatically approved

Method 2

Rate Based BMPs Method Qp=C I A Where Qp=unit peak flow in cfs C=runoff coefficient I=intensity, 2.45 inch per hour A=contributing area in acres Automatic 50% credit

Modification of Rate Based Method Rate Based BMPs Method Use of TR55 to determine Tc Using synthetic storm curve Tc is used to

determine I I declines as Tc increases, thus encouraging

green space by reducing the size of the unit required.

Treatment Train

When one BMP discharges into another Discharge from upstream BMP will be “clean” so

downstream BMP TSS reduction will be less effective

Bioretention80% TSS

Dry Detention60% TSSFlow Flow

TSS reduction = 80+60 – (80x60)/100 = 92%

100

)( BABATSStrain

BMP SELECTION

Ponds

Dry ponds Outlet

structure Dry storage

area 60% TSS

reduction

Ponds

Wet ponds Outlet

structure Permanent

pool 80% TSS

reduction

Ponds

Variations Micropool Extended detention Multiple ponds Pocket ponds

Wetlands

Outlet structure Shallow wet

treatment area Upland dry storage Plants are key Length of flow

(residence time) key 75% TSS reduction

Bioretention areas

Outlet structure Small storm & large

storms Dry treatment area

Depressed planting area

Specific soils Under drain

80% TSS reduction

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

Sand filters

Many variations Best suited for non-

residential Typically underground Must receive drainage

from only impervious surfaces

Infiltration trenches

Limited application due to karst topography

Questions and Discussion

Matt Powell

City of Bowling Green

matt.powell@bgky.org