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Wichita MS4 Program: “Unifying watershed management through an Off-site BMP Implementation
Program”
Ron Graber & Trisha Moore Kansas State University
Spring Stormwater SymposiumMarch 8, 2017
Storm Water Advisory Boardformed 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)
Storm Water Advisory BoardPurpose 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
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)
TMDLs in Wichita’s MS4 permit
• Many TMDL streams influenced by land use upstream of City
• Current TMDL regulated pollutants include Sediment, nutrients & bacteria
How its done Currently
Current Onsite BMP Program
Storm Water Advisory Board
Substantial onsite expense involved What if the SWAB could find a cheaper
method?
WRAPS
Targeted WRAPS
Little Arkansas WatershedAgricultural 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
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
Targeted Areas for Sediment
Load Reduction Needed – 6,571 tons/yr
(40 years)
Priority 1 Priority 2
Cost effectiveness: “Rural” BMPsLittle 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 $2.87Conservation Tillage $20 38% 7.0 $2.87Grassed Waterways $160 40% 18.6 $8.60Vegetative Buffers $67 50% 9.3 $7.17Nutrient Management $57 25% 11.6 $4.88Terraces $102 30% 5.6 $18.28Intensive Crop Rotations $20 25% 4.7 $4.30Cover Crops $60 25% 1.4 $43.01Water Retention Structures $125 50% 9.3 $13.44Permanent Vegetation $500 95% 17.7 $28.30Streambank 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)
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 $5,425Pervious pavement $179,840 88% 9.4 $19,130Extended detention basin $18,465 80% 8.7 $2,120Bioretention $35,500 75% 8 $4,440
Vegetative Buffers $4,500 90% 9.5 $475Grass 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
Evolution of offsite program• Clear: offsite program more effective
economically and, potentially, environmentally• But how to operationalize?
City of Wichita Stormwater Advisory BoardCity 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
MS4 Permit
Provision for offsite BMP program in current MS4 permit (2014)
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
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.
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
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 1Onsite BMP for 40-ac development
Scenario 2Onsite BMP for 1-ac development
Scenario 3Offsite BMP for any development
Marginal Cost for WQv
Excavation $46,464 Outlet Structure $8,000 Total Capital $54,464 Biannual inspection $500
Marginal Cost, hydro. sepHydrodynamic Separator cost $15,000Installation $7,500Total Capital $22,500Biannual inspection $500
$37.60 per acre
development per year
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 residentialOnsite BMP: Hydrodynamic sep. for 1-acre commercialOffsite BMP: $37.60 per acre per year
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 SystemNPDES: Non-Point Discharge Elimination SystemBMP: Best Management Practice
Where we are now City Council supports program – June 17 Authorize start up funds - $60,000 Amend ordinance Execute contract with program administration –August 9 Enrollment as of Jan. 17 - 108 acres urban, 115 acres rural
Onsite developers
City
WRAPS Producers
KDHE, EPA$
$
$
Pollutant reduction credits
Report TSS reductions
Report TSS
reductions
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
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
Ron Graber Watershed Specialist
rgraber@ksu.edu
Trisha Moore Bio & Ag Engineering tlcmoore@ksu.edu
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