The overall goal of this project was to develop an implementation framework for an offsite BMP program
to maximize the environmental and economic effectiveness with which the City of Wichita meets its
NPDES stormwater permitting requirements to ultimately improve water quality in the Little Ark and
Arkansas Rivers. This program aims to integrate watershed stakholders across sociopolitical bounds and
provide a sustainable funding mechanism to implement and maintain water quality practices in the rural
landscape, a critical need as watershed managers struggle to meet water quality targets (e.g., TMDLs).
Based on dialogue between stakeholders representing the watershed’s agricultural (represented by the
Little Ark Watershed Restoration And Protection Strategy program, or WRAPS) and urban (represented by
the City of Wichita’s Stormwater Advisory Board and City officials) communities and the Kansas
Department of Health and Environment (KDHE), which administers TMDLs and water quality permits, the
program works to optimize the placement of BMPs within the watershed for maximum water quality
benefit of the integrated system. Rural management practices tend to be less costly, thereby enabling
greater pollutant load reduction per dollar spent on BMPs in rural versus urban areas. For this reason, net
costs to urban developments participating in the offsite program should be significantly less than if
traditional urban water quality control practices were installed and maintained. A program framework was
developed in which a “sediment credit” fee is paid annually by urban developments participating in the
program to finance implementation and maintenance of offsite BMPs as facilitated through the Little
Arkansas WRAPS program. Adoption of this offsite program is anticipated to lead to greater reductions in
sediment (and other pollutant) loads leaving the watershed than could be achieved through conventional
implementation of BMPs within urban bounds to meet MS4 permit requirements. The program is currently
in its first year of implementation.
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Off-Site BMP Implementation Program
1. Wichita MS4 Program: “Unifying
watershed management through
an Off-site BMP Implementation
Program”
Ron Graber & Trisha Moore
Kansas State University
Spring Stormwater Symposium
March 8, 2017
2. Storm Water Advisory Board
formed November 2011
Greg Allison, PE (Appointed by: City Manager)
Richard Basore - Ex-Officio KDHE Member
Chris Bohm, PE (Appointed by: Wichita Area Builders Assoc.)
Don Kirkland (Appointed by: Wichita Chapter KS Society of
Professional Engineers)
Hoyt Hillman (Appointed by: Sierra Club/WRAPS)
David Leyh (Appointed by: Wichita Area Assoc. of Realtors)
Mitch Mitchell (Appointed by: Sedgwick County Stormwater
Advisory Board)
Gary Oborny (Appointed by: Kansas CCIM)
Joe Pajor, (Appointed by: City of Wichita Public Works & Utilities)
Jim Weber, PE (Appointed by: Sedgwick County Public Works)
3. Storm Water Advisory Board
Purpose and Duties
Advise City Council and staff on storm water
management policy
Review proposed changes to manuals
Comment on matters forwarded by
the Director of Public Works
To frame our actions in conformance with the
MS4 permit and EPA
4. Current Onsite BMP Program
Stormwater discharge from City of Wichita, KS
regulated by MS4 permit (MS4 = Municipal Separated Storm
Sewer)
Permit includes requirement to address TMDLs
within MS4 area
Development and redevelopment required to meet
water quality treatment (> 1 acre)
5. TMDLs in Wichita’s MS4 permit
• Many TMDL
streams
influenced by land
use upstream of
City
• Current TMDL
regulated
pollutants include
Sediment,
nutrients &
bacteria
6. How its done Currently
Current Onsite BMP Program
7. Storm Water Advisory Board
Substantial onsite expense involved
What if the SWAB could find a cheaper
method?
10. Little Arkansas Watershed
Agricultural watershed
913,430 acres
78% cropland
19% grazingland
237 registered CAFO’s
TMDLs set for the watershed
52% of stream segments required
TMDLs
Water quality concerns include
bacteria, nutrients, sediments,
pesticides
Drinking water source for city of
Wichita and numerous smaller cities
and towns
205 public water supplies
7400 groundwater wells
11. WRAPS Implementation Goals
Atrazine from Cropland
Sediment from Cropland
Nutrients from Cropland and Livestock
Fecal Coliform Bacteria from Livestock
Sediment and Nutrients from Streambank and Riparian
Areas
12. Targeted Areas for Sediment
Load Reduction Needed
– 6,571 tons/yr
(40 years)
Priority 1 Priority 2
13. Cost effectiveness: “Rural” BMPs
Little Ark Watershed Cropland BMP Effectiveness
Best Management Practice
Cost Per
Treated
Acre
Erosion
Reduction
Efficiency
Total
Reduction*
Over lifetime $/Ton
No-Till $40 75% 14.0 $2.87
Conservation Tillage $20 38% 7.0 $2.87
Grassed Waterways $160 40% 18.6 $8.60
Vegetative Buffers $67 50% 9.3 $7.17
Nutrient Management $57 25% 11.6 $4.88
Terraces $102 30% 5.6 $18.28
Intensive Crop Rotations $20 25% 4.7 $4.30
Cover Crops $60 25% 1.4 $43.01
Water Retention Structures $125 50% 9.3 $13.44
Permanent Vegetation $500 95% 17.7 $28.30
Streambank stabilization $91/ft 85% 60 $2.30
*Assumes an erosion rate of 1.86 tons/acre/year, with the
exception of streambank stabilization (2.8 tons/ft/yr)
14. Cost effectiveness: “Urban” BMPs
Urban BMP Lifecycle Costs/ton sediment removed
Best Management
Practice
Cost Per
Acre treated
Erosion
Reduction
Efficiency
Sediment
Reduction*
Over lifetime (tons)
$/Ton
sediment
removed
Hydrodynamic
separator $28,750 50% 5.3 $5,425
Pervious pavement $179,840 88% 9.4 $19,130
Extended detention
basin $18,465 80% 8.7 $2,120
Bioretention $35,500 75% 8 $4,440
Vegetative Buffers $4,500 90% 9.5 $475
Grass filter strip $9,600 95% 10.3 $930
*Assumes an Erosion Rate of 0.43 tons/acre/year for Medium
Density Residential or Parking Lot
25-year lifetime assumed for all urban BMPs
15. Evolution of offsite program
• Clear: offsite program more effective
economically and, potentially, environmentally
• But how to operationalize?
City of Wichita Stormwater Advisory Board
City should administer the program WRAPS should administer the
program
Desired to own ground or easements Did not believe ownership was
necessary
Desired to operate/maintain offsite
practices
WRAPS should oversee maintenance
of offsite practices
City should provide reporting WRAPS annual report could meet
reporting requirements
17. Program Framework
Sediment credit ratio
– Ratio serves as “factor of safety” given uncertainty
in actual sediment delivery from offsite sediment
sources to downstream aquatic systems
– 2:1 selected to meet expectations of regulatory
community (KDHE)
1 ton TSS2 tons TSS
18. Program framework
Allowable offsite BMPs
– City’s comfort level with “non-permanent” (e.g.,
no-till) BMPs was initially low
– We accommodated by assuming that sediment
credits provided by non-permanent BMPs would
be replaced. The sediment credit fee reflects this
assumption.
19. Program framework
Sediment credit payment rate
– Developed spreadsheet tool to assist City in setting
payment rate in a transparent manner. Payment
rate based on:
• Cost to producer to adopt AND maintain practice
(selected no-till as a representative and “most-likely”
offsite BMP)
• Cost to replace offsite BMPs should be discontinued
• Administrative costs to enroll and track offsite BMPs
20. Program Framework
Sediment credit fee should (1) cover life-cycle
costs of offsite BMPs while (2) providing some
incentive for program participation. To illustrate:
McCann
Scenario 1
Onsite BMP for 40-ac development
Scenario 2
Onsite BMP for 1-ac development
Scenario 3
Offsite BMP for any developmen
Marginal Cost for WQv
Excavation $46,464
Outlet Structure $8,000
Total Capital $54,464
Biannual
inspection $500
Marginal Cost, hydro. sep
Hydrodynamic
Separator cost $15,000
Installation $7,500
Total Capital $22,500
Biannual
inspection
$500
$37.60 per
acre
development per
year
21. Program framework
Opting to pay an annual, sediment credit fee
to the offsite program is more economic than
traditional onsite measures.
Onsite BMP: pond
for 40-acre
residential
Onsite BMP:
Hydrodynamic sep. for 1-
acre commercial
Offsite BMP: $37.60
per acre per year
22. MS4 NPDES Permit Requirements
July 2014: MS4 permit issued for the City of Wichita now
requires the City to manage post-construction stormwater
runoff quality
Permitted Post-construction stormwater management options
include:
– On-site stormwater quality BMPs (traditional approach)
– Off-site stormwater program
KDHE continues to emphasize the MS4 Permittee should
develop a Stormwater Management Program which works for
their location and circumstances
MS4: Municipal Separated Storm Sewer System
NPDES: Non-Point Discharge Elimination System
BMP: Best Management Practice
23.
24. Where we are now
City Council supports program – June 17
Authorize start up funds - $60,000
Amend ordinance
Execute contract with program administration –August 9
Enrollment as of Jan. 17 - 108 acres urban, 115 acres rural
Onsite developers
City
WRAPS Producers
KDHE, EPA
$
$
$
Report TSS
reductions
25. Timeline
Nov. 2011 – SWAB formed
April 2012 – Ideas brought forward
Feb. 2013 – Brainstorm/ KDHE supportive
Nov. 2013 – WRAPS
June 2014 – RFP
Sept. 2014 – KSU contracted
June 2015 - Final Report
July 2015 – Public outreach
May 2016 – City council meetings
June 2016 – City council approval
Aug. 2016 – Approval to execute contract
Jan. 2017 – First payment to operator
26. What does it take?
Stakeholder buy-in (education)
– KDHE, City of Wichita, Sedgwick County,
development community
Watershed “champion”
– WRAPS – prioritize watershed efforts,
landowner/producer relationships
Monitoring
– Assess changes in eco service provision & adapt as
necessary