HomeMy WebLinkAboutItem VI
PLAN COMMISSION STAFF REPORT JUNE 3, 2025
ITEM VI: MUNICIPAL CODE CHAPTER 14: POST-CONSTRUCTION STORM WATER
MANAGEMENT ORDINANCE UPDATE ANALYSIS
GENERAL INFORMATION
Petitioner/Owner: City of Oshkosh
City Engineering Division Staff, in conjunction with Brown and Caldwell, are currently
evaluating the post-construction pollution control requirements within Municipal Code Chapter
14. The need for this evaluation was originally identified as part of the City of Oshkosh Stormwater
Quality Management Plan, November 2022 (Citywide SWMP), which was approved by the
Common Council (Council) on December 13, 2022. This Citywide SWMP was completed in
response to the completion of the Total Maximum Daily Loads for Total Phosphorus and Total
Suspended Solids Upper Fox and Wolf Basins, February 2020 (Upper Fox and Wolf TMDL) which
was prepared by the Wisconsin Department of Natural Resources (WDNR) and approved by the
Environmental Protection Agency (EPA).
City Staff held a workshop with Council on April 29, 2025 to discuss the history of the City of
Oshkosh’s Stormwater Requirements and the analysis for updating the post-construction numeric
standards of Municipal Code Chapter 14. The workshop was recorded by Oshkosh Media and
can be found using the following link:
https://youtu.be/T9QyKWa8Rw4?list=PLqRylHmMyMndr54ZAonVK3EtZ4NR-g_iM
Staff is looking for a recommendation from the Plan Commission to move forward with one (1) of
the five (5) Scenarios presented to Council. In addition to Plan Commission, we will be giving this
information to Sustainability Advisory Board for a similar recommendation. After Sustainability
Advisory Board and Plan Commission give their recommendations, we will work to make the
changes to Municipal Code Chapter 14 and bring them forward for full approval by Council in
late fall 2025 for implementation on January 1, 2026.
Attachments: April 29, 2025 Council Workshop Handouts (pages 2-43)
May 8, 2025 Council Follow-up Information (pages 44-81)
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TO: Honorable Mayor and Members of the Common Council
FROM: Justin Gierach, Engineering Division Manager / City Engineer
DATE: April 25, 2025
RE: Municipal Code Chapter 14: Post-Construction Stormwater Management
Ordinance Update Analysis
City Engineering Division Staff, in conjunction with Brown and Caldwell, are currently
evaluating the pollution control requirements within Municipal Code Chapter 14. This effort is
partially funded by a grant from the Wisconsin Department of Natural Resources (WDNR). The
resolution authorizing applying for the grant was approved by the Common Council on March
28, 2023 and the Brown and Caldwell agreement associated for this effort was approved on
August 28, 2024.
The need for this evaluation was originally identified as part of the City of Oshkosh Stormwater
Quality Management Plan, November 2022 (Citywide SWMP), which was approved by the
Common Council on December 13, 2022. This Citywide SWMP was completed in response to the
completion of the Total Maximum Daily Loads for Total Phosphorus and Total Suspended Solids Upper
Fox and Wolf Basins, February 2020 (Upper Fox and Wolf TMDL) which was prepared by the
WDNR and approved by the Environmental Protection Agency (EPA).
The Upper Fox and Wolf TMDL establishes limits, called wasteload allocations, on the amount of
Total Phosphorus (TP) and Total Suspended Solids (TSS) that can be discharged into the Fox
River, Lake Winnebago, Lake Butte des Morts, and Sawyer Creek by the City’s Municipal
Separate Storm Sewer System (MS4). WDNR has provided literature for the general public on
what is a TMDL that can be found attached to this memo. The City’s MS4 Permit, which is issued
by the WDNR, contains requirements the City must meet to comply with the TMDL. As part of
this permit, the City must complete various activities related to the storm sewer system, including
making progress towards reducing TSS and TP loads to the levels required by the Upper Fox and
Wolf TMDL.
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One of the approaches that was considered in the Citywide SWMP was to incrementally increase
TP and TSS reduction requirements associated with the City’s Post-Construction Storm Water
Management Code. Several scenarios were evaluated and it was determined that modifying the
current code would positively impact TMDL reductions from new development (existing
greenfield/no impervious surfaces) and redevelopment (existing impervious surfaces) in the City.
Based on that analysis, the Citywide SWMP implementation plan included a recommendation to
conduct an additional evaluation of potential code modifications.
The City first implemented a Post-Construction Storm Water Management Code in the early
1990’s. That Code only contained a peak flow control (flood control) requirement. The last major
code update occurred in 2012, responding to a provision in the City’s MS4 Permit to incorporate
WDNR performance standards contained within NR 151 (WDNR’s code for Runoff
Management) into the Municipal Code that focused on storm water discharge quality. An
Erosion and Sediment Control Code and Illicit Discharge Detection and Elimination Code
were also developed in compliance with MS4 Permit requirements.
The City of Oshkosh is not the first municipality to consider ordinance changes modifying TP
and TSS reduction requirements for new development and redevelopment. As part of the
agreement with Brown and Caldwell, code requirements of other municipalities were reviewed
for their pollution reduction requirements and code applicability. Eight (8) municipalities (half
of those reviewed) have incorporated TMDL reduction requirements.
JER/tlt
Enclosures: Definitions
WDNR TMDL Literature
TMDL Basin Maps
Code Revision Scenarios
SMP Performance Standards
Workshop Presentation
Page 3
–MS4: Municipal Separate Storm Sewer
System
–Reachshed: Drainage area to a waterbody
–SMP: Stormwater Management Practice
–SWMP: Stormwater Management Plan
–TMDL: Total Maximum Daily Load
–The amount of pollution a water body can
receive and still meet water quality standards
–TP: Total Phosphorus
–TSS: Total Suspended Solids
Brown and Caldwell
Background: Definitions
Blue Green Algae – Lake Winnebago (Source: WDNR)
Fernau Watershed - North Main Street Wet Detention Basin
Total Maximum Daily Load (TMDL)
What is a TMDL?
A Total Maximum Daily Load (TMDL) is the maximum amount of a pollutant that a body of water can receive
while still meeting water quality standards. A waterway that exceeds water quality standards is often no longer
suitable for its designated uses, such as wildlife habitat, fishing, or other recreational activities.
Municipal Wastewater
Industrial Wastewater
Stormwater (MS4s)
Naturally occurring from
wetlands and forests
Runoff from the
landscape
TMDL Assessment
In order to develop the
TMDL and answer the
questions above, the
watershed is studied to
determine the amount of
pollution currently entering
the waterway from the
sources shown in the
adjacent figure.
Fish and aquatic life
Recreation
Phosphorus
Toxic algae blooms
Public health risks
Why develop a TMDL?
The ultimate goal of a TMDL is to
improve water quality by reducing
pollutants, such as phosphorus and
sediment. To help achieve this, a
TMDL answers the following
questions:
1. What is the current amount of
pollution entering the waterway
and how much is each source
contributing?
2. How much does pollution need
to be reduced in order for each
waterway to meet water quality
standards?
3. How will the needed pollutant
load reductions be achieved for
each waterway?
A TMDL study and implementation
plan provides a strategic framework
and prioritizes resources for water
quality improvement.
Photo credit: Herbert Lange
Photo credit: Jim Ziegler
Created by Susan Sandford - Wisconsin Department of Natural Resources Bureau of Water Quality Page 5
Brown and Caldwell Page 6
Brown and Caldwell Page 7
Summary of Code Revision Scenarios (4/29/2025)
Code Revisions Scenario Summary
Scenario
TSS Reduction Requirement TP Reduction Requirement
New Development Redevelopment New Development Redevelopment
Current Code 80% 40% None None
Scenario 1 85% 58.4% 57.4% 39.4%
Scenario 2 90% 52% 61% 35%
Scenario 3 80% 58.4% (Sawyer Cr)
40% (Other Areas) 54% 30%
Scenario 4 80% 72.2% 40.5% 40.5%
Scenario 5 80% 58.4% 54% 30%
Page 8
–Considered what could be done
at site to meet different scenarios
–Increased SMP sizes
–i.e. larger wet pond
–Different SMPs
–i.e. Sand filter instead of biofilter
Brown and Caldwell
Analysis: Code Revisions
Potential SMP Performance
TPTSSSMP
>50%> 80%Wet Pond
None80%Biofilter*
35%80%Sand Filter*
35%65%Permeable Pavement*
50%80%Proprietary Filter
15%25%Catch Basin
*TSS/TP reductions can be increased with infiltration.
SMPs listed are accepted as part of WDNR Technical
Standards.
April 29, 2025
Common Council Workshop:
Municipal Code Ch. 14 Update
Page 10
Agenda
1.Background
2.Analysis of Other Communities
3.Analysis of Code Revisions
4.Next Steps
Page 11
–MS4 Permit from DNR requires City to
comply with the TMDL
–Update Council regarding the Municipal
Code Ch. 14 Updates project
–Get input from Council on analysis and
recommendations
Brown and Caldwell
Why are we here?
–City Engineering Division, with Brown and Caldwell (BC), is evaluating
changes to Municipal Code Chapter 14
–Changes focused on stormwater pollution reduction requirements
–Will include other minor revisions
–Partially funded by WDNR Grant
–3/28/2023: Grant application authorized by Common Council
–8/28/2024: BC Contract approved by Common Council
Brown and Caldwell
Background
–Flooding incidents since 1990
–Presidential Disaster Declarations
–1990, 1993, 2001, 2004, 2008
–Other Incidents
–1996, 1999 (2), 2000, 2010, 2012
–Source: Winnebago County Hazard Mitigation Plan
–Project will not modify peak flow
control requirements targeted at
flood reduction
Brown and Caldwell
Background: Flooding
–MS4: Municipal Separate Storm Sewer
System
–Reachshed: Drainage area to a waterbody
–SMP: Stormwater Management Practice
–SWMP: Stormwater Management Plan
–TMDL: Total Maximum Daily Load
–The amount of pollution a water body can
receive and still meet water quality standards
–TP: Total Phosphorus
–TSS: Total Suspended Solids
Brown and Caldwell
Background: Definitions
Blue Green Algae –Lake Winnebago (Source: WDNR)
Fernau Watershed -North Main Street Wet Detention Basin
–City’s storm sewer system is regulated by WDNR Municipal Separate
Storm Sewer System (MS4) General Permit
–Initial permit issued in 2007
–5-year permit cycle
–Last issued in 2019, waiting for updated permit
–TMDL was prepared by WDNR and approved by US EPA (2020)
–Requirements for City associated with TMDL is incorporated into MS4
Permit
–City must make progress towards TMDL requirements
Brown and Caldwell
Background: MS4 Permit
–City Municipal Code governing stormwater management
–Established in the early 1990’s (as Chapter 24)
–Peak flow control requirements only
–Last major revision in 2012 (became Chapter 14)
–Added pollution control (TSS reduction) requirements
–Minor updates in 2014 and 2023
Brown and Caldwell
Background: Chapter 14
–Current Pollution Control
Requirements
–Redevelopment: 40% TSS reduction
–New Development: 80% TSS reduction
–Applies to sites with more than 20,000 ft2
of impervious surface
Brown and Caldwell
Background: Chapter 14
Biofilter at City Hall Parking Lot
Catch basins in 9th Avenue
–Upper Fox and Wolf River TMDL
–Established limits for TP and TSS
–Considers agricultural, industrial,
stormwater, and wastewater
sources
Brown and Caldwell
Background: TMDL
–Established limits the City’s storm
sewer system can discharge to:
–Fox River
–Lake Winnebago
–Lake Butte Des Morts
–Sawyer Creek
–Established limits for the City’s
wastewater treatment plant
Brown and Caldwell
Background: TMDL
–Requirements
Brown and Caldwell
Background: TMDL
TMDL Reach Required TSS
Reduction
Required TP
Reduction
Sawyer Creek 58.4%85.6%
Lake Butte des Morts 20.0%85.6%
Fox River 20.0%85.6%
Lake Winnebago 20.0%85.6%
Neenah Slough (Lower
Fox River TMDL)52.0%40.5%
–November 2022: Most Recent Citywide SWMP completed
–Established City’s current TSS & TP control levels
Reachshed TMDL Target TSS
Load Reduction %
“With Controls”
TSS Reduction %
TMDL Target TP
Load Reduction %
“With Controls” TP
Reduction %
Upper Fox/Wolf TMDL
Sawyer Creek 58.4%28.7%85.6%20.9%
Lake Butte des Morts 20%23.2%85.6%18.3%
Fox River 20%38.3%85.6%28.6%
Lake Winnebago 20%30.8%85.6%24.8%
Lower Fox River TMDL
Neenah Slough 52%0%40.5%0%
Brown and Caldwell
Background: Citywide SWMP
–Considered how City can reduce TSS and TP
–Potential SMPs
–Wet Detention Ponds
–Biofilters
–Rain Gardens
–Enhanced Settling for Wet Ponds
–Revisions to Chapter 14
–Increased requirements for new development and redevelopment
Brown and Caldwell
Background: Citywide SWMP
–Considered Revisions to
Chapter 14
–Evaluated Citywide impact of
future development
–Current code & 2 scenarios
–Evaluated site specific impact to
3 past developments
–Included added evaluation in
implementation plan
Brown and Caldwell
Background: Citywide SWMP
Implementation Plan Element Scheduled Year(s)
Research / integrate additional
existing Non-Regional SMPs
2023 (recent sites)
2024-2025 (older sites)
Additional evaluation of Municipal
Code Modifications 2023-2024
Build WinSLAMM models for
Southwest Industrial Park ponds 2026
Additional leaf management
evaluation 2027
Preliminary design study of enhanced
settling 2028-2029
Citywide SWMP Update –evaluate
new technology and alternative
compliance options (i.e. trading)
2030-2032
–Scope of Work
–Look at what other municipalities are doing.
–Evaluate additional scenarios.
–Consider how changes could impact development sites.
–Communicate with stakeholders.
Brown and Caldwell
Analysis: Current Project
–State Requirements
–Wisconsin Administrative Code NR 151
–Runoff Management
–Redevelopment: 40% TSS Reduction
–New Development: 80% TSS Reduction
–Other municipalities were reviewed
to determine if higher requirements
were implemented
Brown and Caldwell
Analysis: Other Municipal Code Requirements
–Local Ordinance Requires TMDL
Reductions (TSS & TP control)
–Appleton
–Menasha
–Neenah
–Calumet County
–Fox Crossing
–Grand Chute
–Kaukauna
–Outagamie County
–Local Ordinance Requires NR 151
Reductions (TSS control)
–Town of Algoma
–Eau Claire*
–Fond du Lac
–Green Bay
–Janesville
–La Crosse*
–Wausau
–Winnebago County
Brown and Caldwell
Analysis: Other Municipal Code Requirements
*Municipality not within a TMDL area
Other Communities Code Requirements
Brown and Caldwell
City Reachshed
New Development Redevelopment
TSS TP TSS TP
Appleton
Lake Winnebago 80%85.6%40%85.6%
Fox River 80%40.5%72.2%40.5%
Bear Creek 84%85.6%84%85.6%
Garners Creek 80%68.6%59.9%68.6%
Mud Creek 80%48.2%42.8%48.2%
Apple/Duck Creeks 80%40.5%52%40.5%
Neenah
Lake Winnebago 80%-40%-
Neenah Slough 80%41%52%41%
Fox River 80%41%72%41%
Menasha Lake Winnebago 80%60%40%30%
Lower Fox River 80%41%72%41%
–Specific pollution
reduction
requirements from
selected communities
with TMDL reduction
requirements
Page 28
–Criteria
–Progress toward TMDL
–Feasible for sites to meet targets
–Consider Cost
Brown and Caldwell
Analysis: Code Revisions
–Pollution reduction scenarios considered
–Developed scenarios based on TMDL, SMP effectiveness, and nearby
community requirements
Brown and Caldwell
Analysis: Code Revisions
Code Revisions Scenario Summary
Scenario
TSS Reduction Requirement TP Reduction Requirement
New
Development Redevelopment
New
Development Redevelopment
Current Code 80%40%None None
Scenario 1 85%58.4%57.4%39.4%
Scenario 2 90%52%61%35%
Scenario 3 80%58.4% (Sawyer Cr)
40% (Other Areas)54%30%
Scenario 4 80% 72.2% 40.5% 40.5%
Scenario 5 80%58.4%54%30%
–MS4 Permit requires continual progress each permit term
towards TMDL numeric standards
–Assessing Progress Towards TMDL
–Considered Citywide Impact of Code Changes
–Used a 30-year planning horizon
–Projected rate of development based on past
–Would not fully comply with TMDL targets under any scenario
–Amount of anticipated new development and re-development happening over the next 30-years is limited
–Additional SMPs will have to be designed and installed by the City to treat existing development
Brown and Caldwell
Analysis: Code Revisions
–Redevelopment Sites Evaluated
–Ceape / Otter Parking Lot*
–Field Operations Facility*
–Freddy’s Oshkosh**
–New Development Sites Evaluated
–The Wit Apartment Complex*
–Valley Veterinary Hospital**
Brown and Caldwell
Analysis: Code Revisions
Permeable Pavement at Ceape/Otter Parking Lot
Biofilter at Field Operations Facility
*Site evaluated as part of Citywide SWMP.
**Site evaluated as part of current project.
–Considered what could be done
at site to meet different scenarios
–Increased SMP sizes
–i.e. larger wet pond
–Different SMPs
–i.e. Sand filter instead of biofilter
Brown and Caldwell
Analysis: Code Revisions
Potential SMP Performance
SMP TSS TP
Wet Pond > 80%>50%
Biofilter*80%None
Sand Filter*80%35%
Permeable Pavement*65%35%
Proprietary Filter 80%50%
Catch Basin 25%15%
*TSS/TP reductions can be increased with infiltration.
SMPs listed are accepted as part of WDNR Technical
Standards.
–Does existing
site design
meet code
scenarios?
Redevelopment Site
(current TSS / TP reductions)
Would Updated Municipal Code be Met? (Redevelopment)
Scenario 1
(58.4% TSS /
39.4% TP)
Scenario 2
(52% TSS /
35% TP)
Scenario 3
(58.4% TSS /
30% TP)
Scenario 4
(72.2% TSS /
40.5% TP)
Scenario 5
(58.4% TSS /
30% TP)
Ceape/Otter Parking*
(63.2% TSS / 34.7% TP)
Partial
(TSS only)
Partial
(TSS only)Yes No Yes
Field Operations*
(56.8% TSS / 23.1% TP)No Partial
(TSS only)No No No
Freddy’s Oshkosh**
(42.9% TSS / 36.3% TP)No Partial
(TP only)
Partial
(TP only)No Partial
(TP only)
Brown and Caldwell
Analysis:
Code Revisions
*Site evaluated as part of Citywide SWMP.
**Site evaluated as part of current project.
New Development Site
(current TSS / TP reductions)
Would Updated Municipal Code be Met? (New Development)
Scenario 1
(85% TSS /
57.4% TP)
Scenario 2
(90% TSS /
61% TP)
Scenario 3
(80% TSS /
54% TP)
Scenario 4
(80% TSS /
40.5% TP)
Scenario 5
(80% TSS /
54% TP)
The Wit Apartments*
(85.5% TSS / 62.7% TP)Yes Partial
(TP only)Yes Yes Yes
Valley Vet. Hospital**
(80.0% TSS / 35.0% TP)No No Partial
(TSS only)
Partial
(TSS only)
Partial
(TSS only)
–Is it feasible to
meet scenarios?
–Evaluated
potential site
changes that
could be used to
meet an updated
municipal code
Redevelopment
Site
Could Updated Municipal Code be Met? (Redevelopment)
Scenario 1
(58.4% TSS
/ 39.4% TP)
Scenario 2
(52% TSS /
35% TP)
Scenario 3
(58.4% TSS
/ 30% TP)
Scenario 4
(72.2% TSS
/ 40.5% TP)
Scenario 5
(58.4% TSS
/ 30% TP)
Ceape/Otter
Parking*Yes Yes Yes No Yes
Field Operations
Facility*Yes Yes Yes No Yes
Freddy’s
Oshkosh**Yes Yes Yes Yes Yes
Brown and Caldwell
Analysis:
Site Revisions
*Site evaluated as part of Citywide SWMP.
**Site evaluated as part of current project.
New
Development
Site
Could Updated Municipal Code be Met? (New Development)
Scenario 1
(85% TSS /
57.4% TP)
Scenario 2
(90% TSS /
61% TP)
Scenario 3
(80% TSS /
54% TP)
Scenario 4
(80% TSS /
40.5% TP)
Scenario 5
(80% TSS /
54% TP)
The Wit
Apartment
Complex*
Yes Yes Yes Yes Yes
Valley Veterinary
Hospital**
Partial
(TSS only)No Yes Yes Yes
Brown and Caldwell
Potential Site Impacts: Freddy’s Oshkosh
Alternative
TSS Load
Reduction
(%)
TP Load
Reduction
(%)
Is Municipal Code Met?
Current Scenario 1 Scenario 2 Scenario 3 Scenario 4 Scenario 5
TSS
(40%)
TP
(N/A)
TSS
(58.4%)
TP
(39.4%)
TSS
(52%)
TP
(35%)
TSS
(58.4%)
TP
(30%)
TSS
(72.2%)
TP
(40.5%)
TSS
(58.4%)
TP
(30%)
Site Design 42.9%36.3%Yes N/A No No No Yes No Yes No No No Yes
Alt. 1 53.7%42.3%Yes N/A No Yes Yes Yes No Yes No Yes No Yes
Alt. 2 58.6%35.8%Yes N/A Yes No Yes Yes Yes Yes No No Yes Yes
Alt. 3 72.5%57.2%Yes N/A Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
Alt. 4 66.1%49.0%Yes N/A Yes Yes Yes Yes Yes Yes No Yes Yes Yes
Alt. 5 64.9%72.2%Yes N/A Yes Yes Yes Yes Yes Yes No Yes Yes Yes
–Site Design: 6 –4’ dia catch basins with sumps & grass swale
–Alternative 1: 6 -10’ dia catch basins with sumps & grass swale
–Alternative 2: 2 –800 sq ft underground detention areas (no catch basins or swales)
–Alternative 3: 2 permeable pavement areas (2,500 sq ft and 3,000 sq ft; 0.5 in/hr infiltration rate)
–Alternative 4: 2 –400 sq ft sand filters (2 –4’ dia catch basins and grass swale remain)
–Alternative 5: Proprietary filter
Page 36
Brown and Caldwell
Potential Site Impacts: Freddy’s Oshkosh
Alternative SMPs Estimated
Construction Cost
Estimated Annual
Maintenance Cost
Estimated
Non-Routine
Maintenance Cost
Total Annualized
Cost
Site Design 6 -Catch Basins (4' dia), Grass
Swale $35,600 $400 N/A $2,100
Alt. 1 10' dia Catch Basins, Grass Swale $150,000 $1,400 N/A $8,400
Alt. 2 2 -800 sq ft Underground Detention
Area $192,000 $400 $4,400 $9,800
Alt. 3 2,500 & 3,000 sq ft Permeable
Pavement Areas $207,800 $200 $12,375 $13,700
Alt. 4 2 -400 sq ft Sand Filters, Grass
Swale, 2 -Catch Basins (4' dia)$43,900 $2,000 $17,800 $5,400
Alt. 5 Proprietary Filter $42,400 $3,300 N/A $5,300
–All SMPs: 4% Interest rate, 50-year lifespan
–Catch Basins: Annual cleaning
–Permeable Pavement: Annual site inspection, cleaning every 3-years,
resealing every 5-year
–Proprietary Filter: Annual cleaning & filter replacement
–Sand Filter: Annual inspection & minor maintenance, rehabilitation every
20-years
–Underground Detention: Annual inspection, sediment removal every 15-
years Page 37
Brown and Caldwell
Potential Site Impacts: Valley Veterinary Hospital
Alternative
TSS Load
Reduction
(%)
TP Load
Reduction
(%)
Is Municipal Code Met?
Current Scenario 1 Scenario 2 Scenario 3 Scenario 4 Scenario 5
TSS
(80%)
TP
(N/A)
TSS
(85%)
TP
(57.4%)
TSS
(90%)
TP
(61%)
TSS
(80%)
TP
(54%)
TSS
(80%)
TP
(40.5%)
TSS
(80%)
TP
(54%)
Site Design 80.0%35.0%Yes N/A No No No No Yes No Yes No Yes No
Alt. 1 86.6%57.1%Yes N/A Yes No No No Yes Yes Yes Yes Yes Yes
Alt. 2 80.5%60.2%Yes N/A No Yes No No Yes Yes Yes Yes Yes Yes
–Site Design: Sand filter with clay liner (no infiltration)
–Alternative 1: Sand filter with infiltration rate of 0.24 in/hr (same footprint as designed sand filter)
–Alternative 2: Wet detention basin in place of biofilter (3-inch orifice outlet, 0.05 acre permanent pool)
Page 38
Brown and Caldwell
Potential Site Impacts: Valley Veterinary Hospital
Alternative SMPs Estimated
Construction Cost
Estimated Annual
Maintenance Cost
Estimated
Non-Routine
Maintenance Cost
Total
Annualized
Cost
Site Design Sand Filter $92,600 $845 $30,200 $7,400
Alt. 1 Over-excavated Sand Filter $103,300 $845 $51,500 $9,500
Alt. 2 Wet Pond $87,600 $800 $16,000 $5,800
–All SMPs: 4% Interest rate, 50-year lifespan
–Sand Filter: Annual inspection & minor maintenance, rehabilitation every 20-years (assumes replacement of top half of sand media)
–Wet Pond: Site inspection & minor maintenance, dredging every 35-years
Page 39
1.Site specific conditions can limit potential SMPs that are applicable
2.Peak flow control requirements often result in site exceeding current
TSS reduction targets
3.Impact of infiltration (even at low rates) can be significant
4.Cost impacted by variety of factors
5.Higher reduction requirements will lead to more maximum extent
practicable requests
Brown and Caldwell
Analysis: Takeaways
Page 40
–Pending direction from Common Council
–Which scenario would you like us to move forward with?
–Next Steps Proposed
–Sustainability Advisory Board Recommendations
–Plan Commission Recommendations
–Revise Code Language
–Council Approval of Code Updates
–Complete by End of 2025 (Grant Deadline)
Brown and Caldwell
Next Steps
–Questions?
Thank you.
Page 42
Brown and Caldwell Page 43
TO:Honorable Mayor and Members of the Common Council
FROM:Justin Gierach, Engineering Division Manager/City Engineer
DATE:May 13, 2025
SUBJECT:Municipal Code Chapter 14: Post-Construction Storm Water Management
Ordinance Update Analysis – Follow-up
BACKGROUND
As a follow up to the workshop (Oshkosh Media recording of the workshop) from April 29,
2025, the Common Council (Council) had asked for further analyses of additional sites to
see how they would compare to the different scenarios. The additional sites were a
combination of new and redevelopment, and were slightly more recent than the ones that
were originally studied.
As you can see by the attached Updated Site Scenario analysis, Scenario 3 was the only
scenario that each of the sites met both the TSS and TP for the newly-studied Red Earth
Development (new development), Mill on Main (redevelopment), and ThedaCare
(redevelopment). Please note that this conclusion was somewhat expected, as the current
code would have required the 40% TSS removal for the redevelopment sites to be in
compliance and none of these sites were in the Sawyer Creek Reachshed, which is the only
reachshed that has the higher 58.4% TSS removal requirements.
Staff intend to take this information to the Sustainability Advisory Board on June 2, 2025 and
Plan Commission on June 3, 2025 for a scenario recommendation to Council. Once staff
has the recommendations from these advisory boards, we will work to make the changes to
Chapter 14 and bring them forward for full approval by Council in late fall.
Attachments
24-24 Workshop slides
24-24 Code Revision scenarios
24-24 Updated site scenario analysis
Page 44
April 29, 2025
Common Council Workshop:
Municipal Code Ch. 14 Update
Page 45
Agenda
1.Background
2.Analysis of Other Communities
3.Analysis of Code Revisions
4.Next Steps
Page 46
–MS4 Permit from DNR requires City to
comply with the TMDL
–Update Council regarding the Municipal
Code Ch. 14 Updates project
–Get input from Council on analysis and
recommendations
Brown and Caldwell
Why are we here?
–City Engineering Division, with Brown and Caldwell (BC), is evaluating
changes to Municipal Code Chapter 14
–Changes focused on stormwater pollution reduction requirements
–Will include other minor revisions
–Partially funded by WDNR Grant
–3/28/2023: Grant application authorized by Common Council
–8/28/2024: BC Contract approved by Common Council
Brown and Caldwell
Background
–Flooding incidents since 1990
–Presidential Disaster Declarations
–1990, 1993, 2001, 2004, 2008
–Other Incidents
–1996, 1999 (2), 2000, 2010, 2012
–Source: Winnebago County Hazard Mitigation Plan
–Project will not modify peak flow
control requirements targeted at
flood reduction
Brown and Caldwell
Background: Flooding
–MS4: Municipal Separate Storm Sewer
System
–Reachshed: Drainage area to a waterbody
–SMP: Stormwater Management Practice
–SWMP: Stormwater Management Plan
–TMDL: Total Maximum Daily Load
–The amount of pollution a water body can
receive and still meet water quality standards
–TP: Total Phosphorus
–TSS: Total Suspended Solids
Brown and Caldwell
Background: Definitions
Blue Green Algae –Lake Winnebago (Source: WDNR)
Fernau Watershed -North Main Street Wet Detention Basin
–City’s storm sewer system is regulated by WDNR Municipal Separate
Storm Sewer System (MS4) General Permit
–Initial permit issued in 2007
–5-year permit cycle
–Last issued in 2019, waiting for updated permit
–TMDL was prepared by WDNR and approved by US EPA (2020)
–Requirements for City associated with TMDL is incorporated into MS4
Permit
–City must make progress towards TMDL requirements
Brown and Caldwell
Background: MS4 Permit
–City Municipal Code governing stormwater management
–Established in the early 1990’s (as Chapter 24)
–Peak flow control requirements only
–Last major revision in 2012 (became Chapter 14)
–Added pollution control (TSS reduction) requirements
–Minor updates in 2014 and 2023
Brown and Caldwell
Background: Chapter 14
–Current Pollution Control
Requirements
–Redevelopment: 40% TSS reduction
–New Development: 80% TSS reduction
–Applies to sites with more than 20,000 ft2
of impervious surface
Brown and Caldwell
Background: Chapter 14
Biofilter at City Hall Parking Lot
Catch basins in 9th Avenue
–Upper Fox and Wolf River TMDL
–Established limits for TP and TSS
–Considers agricultural, industrial,
stormwater, and wastewater
sources
Brown and Caldwell
Background: TMDL
–Established limits the City’s storm
sewer system can discharge to:
–Fox River
–Lake Winnebago
–Lake Butte Des Morts
–Sawyer Creek
–Established limits for the City’s
wastewater treatment plant
Brown and Caldwell
Background: TMDL
–Requirements
Brown and Caldwell
Background: TMDL
TMDL Reach Required TSS
Reduction
Required TP
Reduction
Sawyer Creek 58.4%85.6%
Lake Butte des Morts 20.0%85.6%
Fox River 20.0%85.6%
Lake Winnebago 20.0%85.6%
Neenah Slough (Lower
Fox River TMDL)52.0%40.5%
–November 2022: Most Recent Citywide SWMP completed
–Established City’s current TSS & TP control levels
Reachshed TMDL Target TSS
Load Reduction %
“With Controls”
TSS Reduction %
TMDL Target TP
Load Reduction %
“With Controls” TP
Reduction %
Upper Fox/Wolf TMDL
Sawyer Creek 58.4%28.7%85.6%20.9%
Lake Butte des Morts 20%23.2%85.6%18.3%
Fox River 20%38.3%85.6%28.6%
Lake Winnebago 20%30.8%85.6%24.8%
Lower Fox River TMDL
Neenah Slough 52%0%40.5%0%
Brown and Caldwell
Background: Citywide SWMP
–Considered how City can reduce TSS and TP
–Potential SMPs
–Wet Detention Ponds
–Biofilters
–Rain Gardens
–Enhanced Settling for Wet Ponds
–Revisions to Chapter 14
–Increased requirements for new development and redevelopment
Brown and Caldwell
Background: Citywide SWMP
–Considered Revisions to
Chapter 14
–Evaluated Citywide impact of
future development
–Current code & 2 scenarios
–Evaluated site specific impact to
3 past developments
–Included added evaluation in
implementation plan
Brown and Caldwell
Background: Citywide SWMP
Implementation Plan Element Scheduled Year(s)
Research / integrate additional
existing Non-Regional SMPs
2023 (recent sites)
2024-2025 (older sites)
Additional evaluation of Municipal
Code Modifications 2023-2024
Build WinSLAMM models for
Southwest Industrial Park ponds 2026
Additional leaf management
evaluation 2027
Preliminary design study of enhanced
settling 2028-2029
Citywide SWMP Update –evaluate
new technology and alternative
compliance options (i.e. trading)
2030-2032
–Scope of Work
–Look at what other municipalities are doing.
–Evaluate additional scenarios.
–Consider how changes could impact development sites.
–Communicate with stakeholders.
Brown and Caldwell
Analysis: Current Project
–State Requirements
–Wisconsin Administrative Code NR 151
–Runoff Management
–Redevelopment: 40% TSS Reduction
–New Development: 80% TSS Reduction
–Other municipalities were reviewed
to determine if higher requirements
were implemented
Brown and Caldwell
Analysis: Other Municipal Code Requirements
–Local Ordinance Requires TMDL
Reductions (TSS & TP control)
–Appleton
–Menasha
–Neenah
–Calumet County
–Fox Crossing
–Grand Chute
–Kaukauna
–Outagamie County
–Local Ordinance Requires NR 151
Reductions (TSS control)
–Town of Algoma
–Eau Claire*
–Fond du Lac
–Green Bay
–Janesville
–La Crosse*
–Wausau
–Winnebago County
Brown and Caldwell
Analysis: Other Municipal Code Requirements
*Municipality not within a TMDL area
Other Communities Code Requirements
Brown and Caldwell
City Reachshed
New Development Redevelopment
TSS TP TSS TP
Appleton
Lake Winnebago 80%85.6%40%85.6%
Fox River 80%40.5%72.2%40.5%
Bear Creek 84%85.6%84%85.6%
Garners Creek 80%68.6%59.9%68.6%
Mud Creek 80%48.2%42.8%48.2%
Apple/Duck Creeks 80%40.5%52%40.5%
Neenah
Lake Winnebago 80%-40%-
Neenah Slough 80%41%52%41%
Fox River 80%41%72%41%
Menasha Lake Winnebago 80%60%40%30%
Lower Fox River 80%41%72%41%
–Specific pollution
reduction
requirements from
selected communities
with TMDL reduction
requirements
Page 63
–Criteria
–Progress toward TMDL
–Feasible for sites to meet targets
–Consider Cost
Brown and Caldwell
Analysis: Code Revisions
–Pollution reduction scenarios considered
–Developed scenarios based on TMDL, SMP effectiveness, and nearby
community requirements
Brown and Caldwell
Analysis: Code Revisions
Code Revisions Scenario Summary
Scenario
TSS Reduction Requirement TP Reduction Requirement
New
Development Redevelopment
New
Development Redevelopment
Current Code 80%40%None None
Scenario 1 85%58.4%57.4%39.4%
Scenario 2 90%52%61%35%
Scenario 3 80%58.4% (Sawyer Cr)
40% (Other Areas)54%30%
Scenario 4 80% 72.2% 40.5% 40.5%
Scenario 5 80%58.4%54%30%
–MS4 Permit requires continual progress each permit term
towards TMDL numeric standards
–Assessing Progress Towards TMDL
–Considered Citywide Impact of Code Changes
–Used a 30-year planning horizon
–Projected rate of development based on past
–Would not fully comply with TMDL targets under any scenario
–Amount of anticipated new development and re-development happening over the next 30-years is limited
–Additional SMPs will have to be designed and installed by the City to treat existing development
Brown and Caldwell
Analysis: Code Revisions
–Redevelopment Sites Evaluated
–Ceape / Otter Parking Lot*
–Field Operations Facility*
–Freddy’s Oshkosh**
–New Development Sites Evaluated
–The Wit Apartment Complex*
–Valley Veterinary Hospital**
Brown and Caldwell
Analysis: Code Revisions
Permeable Pavement at Ceape/Otter Parking Lot
Biofilter at Field Operations Facility
*Site evaluated as part of Citywide SWMP.
**Site evaluated as part of current project.
–Considered what could be done
at site to meet different scenarios
–Increased SMP sizes
–i.e. larger wet pond
–Different SMPs
–i.e. Sand filter instead of biofilter
Brown and Caldwell
Analysis: Code Revisions
Potential SMP Performance
SMP TSS TP
Wet Pond > 80%>50%
Biofilter*80%None
Sand Filter*80%35%
Permeable Pavement*65%35%
Proprietary Filter 80%50%
Catch Basin 25%15%
*TSS/TP reductions can be increased with infiltration.
SMPs listed are accepted as part of WDNR Technical
Standards.
–Does existing
site design
meet code
scenarios?
Redevelopment Site
(current TSS / TP reductions)
Would Updated Municipal Code be Met? (Redevelopment)
Scenario 1
(58.4% TSS /
39.4% TP)
Scenario 2
(52% TSS /
35% TP)
Scenario 3
(58.4% TSS /
30% TP)
Scenario 4
(72.2% TSS /
40.5% TP)
Scenario 5
(58.4% TSS /
30% TP)
Ceape/Otter Parking*
(63.2% TSS / 34.7% TP)
Partial
(TSS only)
Partial
(TSS only)Yes No Yes
Field Operations*
(56.8% TSS / 23.1% TP)No Partial
(TSS only)No No No
Freddy’s Oshkosh**
(42.9% TSS / 36.3% TP)No Partial
(TP only)
Partial
(TP only)No Partial
(TP only)
Brown and Caldwell
Analysis:
Code Revisions
*Site evaluated as part of Citywide SWMP.
**Site evaluated as part of current project.
New Development Site
(current TSS / TP reductions)
Would Updated Municipal Code be Met? (New Development)
Scenario 1
(85% TSS /
57.4% TP)
Scenario 2
(90% TSS /
61% TP)
Scenario 3
(80% TSS /
54% TP)
Scenario 4
(80% TSS /
40.5% TP)
Scenario 5
(80% TSS /
54% TP)
The Wit Apartments*
(85.5% TSS / 62.7% TP)Yes Partial
(TP only)Yes Yes Yes
Valley Vet. Hospital**
(80.0% TSS / 35.0% TP)No No Partial
(TSS only)
Partial
(TSS only)
Partial
(TSS only)
–Is it feasible to
meet scenarios?
–Evaluated
potential site
changes that
could be used to
meet an updated
municipal code
Redevelopment
Site
Could Updated Municipal Code be Met? (Redevelopment)
Scenario 1
(58.4% TSS
/ 39.4% TP)
Scenario 2
(52% TSS /
35% TP)
Scenario 3
(58.4% TSS
/ 30% TP)
Scenario 4
(72.2% TSS
/ 40.5% TP)
Scenario 5
(58.4% TSS
/ 30% TP)
Ceape/Otter
Parking*Yes Yes Yes No Yes
Field Operations
Facility*Yes Yes Yes No Yes
Freddy’s
Oshkosh**Yes Yes Yes Yes Yes
Brown and Caldwell
Analysis:
Site Revisions
*Site evaluated as part of Citywide SWMP.
**Site evaluated as part of current project.
New
Development
Site
Could Updated Municipal Code be Met? (New Development)
Scenario 1
(85% TSS /
57.4% TP)
Scenario 2
(90% TSS /
61% TP)
Scenario 3
(80% TSS /
54% TP)
Scenario 4
(80% TSS /
40.5% TP)
Scenario 5
(80% TSS /
54% TP)
The Wit
Apartment
Complex*
Yes Yes Yes Yes Yes
Valley Veterinary
Hospital**
Partial
(TSS only)No Yes Yes Yes
Brown and Caldwell
Potential Site Impacts: Freddy’s Oshkosh
Alternative
TSS Load
Reduction
(%)
TP Load
Reduction
(%)
Is Municipal Code Met?
Current Scenario 1 Scenario 2 Scenario 3 Scenario 4 Scenario 5
TSS
(40%)
TP
(N/A)
TSS
(58.4%)
TP
(39.4%)
TSS
(52%)
TP
(35%)
TSS
(58.4%)
TP
(30%)
TSS
(72.2%)
TP
(40.5%)
TSS
(58.4%)
TP
(30%)
Site Design 42.9%36.3%Yes N/A No No No Yes No Yes No No No Yes
Alt. 1 53.7%42.3%Yes N/A No Yes Yes Yes No Yes No Yes No Yes
Alt. 2 58.6%35.8%Yes N/A Yes No Yes Yes Yes Yes No No Yes Yes
Alt. 3 72.5%57.2%Yes N/A Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
Alt. 4 66.1%49.0%Yes N/A Yes Yes Yes Yes Yes Yes No Yes Yes Yes
Alt. 5 64.9%72.2%Yes N/A Yes Yes Yes Yes Yes Yes No Yes Yes Yes
–Site Design: 6 –4’ dia catch basins with sumps & grass swale
–Alternative 1: 6 -10’ dia catch basins with sumps & grass swale
–Alternative 2: 2 –800 sq ft underground detention areas (no catch basins or swales)
–Alternative 3: 2 permeable pavement areas (2,500 sq ft and 3,000 sq ft; 0.5 in/hr infiltration rate)
–Alternative 4: 2 –400 sq ft sand filters (2 –4’ dia catch basins and grass swale remain)
–Alternative 5: Proprietary filter
Page 71
Brown and Caldwell
Potential Site Impacts: Freddy’s Oshkosh
Alternative SMPs Estimated
Construction Cost
Estimated Annual
Maintenance Cost
Estimated
Non-Routine
Maintenance Cost
Total Annualized
Cost
Site Design 6 -Catch Basins (4' dia), Grass
Swale $35,600 $400 N/A $2,100
Alt. 1 10' dia Catch Basins, Grass Swale $150,000 $1,400 N/A $8,400
Alt. 2 2 -800 sq ft Underground Detention
Area $192,000 $400 $4,400 $9,800
Alt. 3 2,500 & 3,000 sq ft Permeable
Pavement Areas $207,800 $200 $12,375 $13,700
Alt. 4 2 -400 sq ft Sand Filters, Grass
Swale, 2 -Catch Basins (4' dia)$43,900 $2,000 $17,800 $5,400
Alt. 5 Proprietary Filter $42,400 $3,300 N/A $5,300
–All SMPs: 4% Interest rate, 50-year lifespan
–Catch Basins: Annual cleaning
–Permeable Pavement: Annual site inspection, cleaning every 3-years,
resealing every 5-year
–Proprietary Filter: Annual cleaning & filter replacement
–Sand Filter: Annual inspection & minor maintenance, rehabilitation every
20-years
–Underground Detention: Annual inspection, sediment removal every 15-
years Page 72
Brown and Caldwell
Potential Site Impacts: Valley Veterinary Hospital
Alternative
TSS Load
Reduction
(%)
TP Load
Reduction
(%)
Is Municipal Code Met?
Current Scenario 1 Scenario 2 Scenario 3 Scenario 4 Scenario 5
TSS
(80%)
TP
(N/A)
TSS
(85%)
TP
(57.4%)
TSS
(90%)
TP
(61%)
TSS
(80%)
TP
(54%)
TSS
(80%)
TP
(40.5%)
TSS
(80%)
TP
(54%)
Site Design 80.0%35.0%Yes N/A No No No No Yes No Yes No Yes No
Alt. 1 86.6%57.1%Yes N/A Yes No No No Yes Yes Yes Yes Yes Yes
Alt. 2 80.5%60.2%Yes N/A No Yes No No Yes Yes Yes Yes Yes Yes
–Site Design: Sand filter with clay liner (no infiltration)
–Alternative 1: Sand filter with infiltration rate of 0.24 in/hr (same footprint as designed sand filter)
–Alternative 2: Wet detention basin in place of biofilter (3-inch orifice outlet, 0.05 acre permanent pool)
Page 73
Brown and Caldwell
Potential Site Impacts: Valley Veterinary Hospital
Alternative SMPs Estimated
Construction Cost
Estimated Annual
Maintenance Cost
Estimated
Non-Routine
Maintenance Cost
Total
Annualized
Cost
Site Design Sand Filter $92,600 $845 $30,200 $7,400
Alt. 1 Over-excavated Sand Filter $103,300 $845 $51,500 $9,500
Alt. 2 Wet Pond $87,600 $800 $16,000 $5,800
–All SMPs: 4% Interest rate, 50-year lifespan
–Sand Filter: Annual inspection & minor maintenance, rehabilitation every 20-years (assumes replacement of top half of sand media)
–Wet Pond: Site inspection & minor maintenance, dredging every 35-years
Page 74
1.Site specific conditions can limit potential SMPs that are applicable
2.Peak flow control requirements often result in site exceeding current
TSS reduction targets
3.Impact of infiltration (even at low rates) can be significant
4.Cost impacted by variety of factors
5.Higher reduction requirements will lead to more maximum extent
practicable requests
Brown and Caldwell
Analysis: Takeaways
Page 75
–Pending direction from Common Council
–Which scenario would you like us to move forward with?
–Next Steps Proposed
–Sustainability Advisory Board Recommendations
–Plan Commission Recommendations
–Revise Code Language
–Council Approval of Code Updates
–Complete by End of 2025 (Grant Deadline)
Brown and Caldwell
Next Steps
–Questions?
Thank you.
Page 77
Brown and Caldwell Page 78
Summary of Code Revision Scenarios (4/29/2025)
Code Revisions Scenario Summary
Scenario
TSS Reduction Requirement TP Reduction Requirement
New Development Redevelopment New Development Redevelopment
Current Code 80% 40% None None
Scenario 1 85% 58.4% 57.4% 39.4%
Scenario 2 90% 52% 61% 35%
Scenario 3 80% 58.4% (Sawyer Cr)
40% (Other Areas) 54% 30%
Scenario 4 80% 72.2% 40.5% 40.5%
Scenario 5 80% 58.4% 54% 30%
Page 79
–Does existing
site design
meet code
scenarios?
–Redevelopment
projects
Would Updated Municipal Code be Met? (Redevelopment)
Redevelopment Site
(current TSS / TP reductions)
Scenario 5
(58.4% TSS /
30% TP)
Scenario 4
(72.2% TSS /
40.5% TP)
Scenario 3
(58.4% or
40% TSS /
30% TP)
Scenario 2
(52% TSS /
35% TP)
Scenario 1
(58.4% TSS /
39.4% TP)
YesNoYesPartial
(TSS only)
Partial
(TSS only)
Ceape/Otter Parking*
(63.2% TSS / 34.7% TP)
NoNoPartial
(TSS only)
Partial
(TSS only)NoField Operations*
(56.8% TSS / 23.1% TP)
Partial
(TP only)NoPartial
(TP only)
Partial
(TP only)NoFreddy’s Oshkosh**
(42.9% TSS / 36.3% TP)
Partial
(TP only)NoYesYesNoMill on Main**
(56.1% TSS / 39.0% TP)
Partial
(TP only)
Partial
(TP only)YesPartial
(TP only)
Partial
(TP only)
Thedacare**
(49.8% TSS / 54.7% TP)
Brown and Caldwell
Analysis:
Code Revisions
*Site evaluated as part of Citywide SWMP.
**Site evaluated as part of current project.
Page 80
–Does existing
site design
meet code
scenarios?
–New
Development
Projects
Brown and Caldwell
Analysis:
Code Revisions
*Site evaluated as part of Citywide SWMP.
**Site evaluated as part of current project.
Would Updated Municipal Code be Met? (New Development)
New Development Site
(current TSS / TP reductions)
Scenario 5
(80% TSS /
54% TP)
Scenario 4
(80% TSS /
40.5% TP)
Scenario 3
(80% TSS /
54% TP)
Scenario 2
(90% TSS /
61% TP)
Scenario 1
(85% TSS /
57.4% TP)
YesYesYesPartial
(TP only)YesThe Wit Apartments*
(85.5% TSS / 62.7% TP)
Partial
(TSS only)
Partial
(TSS only)
Partial
(TSS only)NoNoValley Vet. Hospital**
(80.0% TSS / 35.0% TP)
YesYesYesPartial
(TP only)
Partial
(TP only)
Red Earth
Development**
(83.7% / 62.1% TP)
Page 81