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Stormwater Management Improvements
Public Meeting March 13, 2013
Stormwater Management Improvements Public Meeting March 13, 2013 - - PowerPoint PPT Presentation
Stormwater Management Improvements Public Meeting March 13, 2013 - - PowerPoint PPT Presentation
Stormwater Management Improvements Public Meeting March 13, 2013 Village Aerial Combined Sewer System Sewer Surcharging Sewer System Overview Estimated in 2001 that the Villages system has the capacity to handle a 2-3 year storm
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Combined Sewer System
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Sewer Surcharging
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Sewer System Overview
Estimated in 2001 that the Village’s system
has the capacity to handle a 2-3 year storm (approximately 1.7 inches in 2 hours)
Periodic reports of sewers surcharging into
basements and streets
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Flooding is Not a Recent Phenomenon
Significant storms have occurred in:
1956, 1962, 1969, 1972, 1981, 2001, 9/08, 6/09
Following the 1981 storms, Village begins
installing surface storm sewer restrictors
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Not Restricted Restricted
Curb Inlets
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Approximately 70-75% of sewers are restricted within the Village Restricted Unrestricted
Catch Basin Covers
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Village Flood Survey
August 2, 2001 Storm
3” rain received in 2 hours 25 year rain event
The Village surveyed all residents to determine
extent and type of flooding
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August 2, 2001 Flooding (35% response rate to survey)
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Storm estimated to be a 3.5 year event, data based on 134 phone calls received. September 13 & 14 2008 Flooding
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Sewage in Basement
June 19, 2009 Storm Reports of Sewage in Basement 2-3 Year Event, 160 Phone Calls
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Incremental Village Actions
2004 Adopted a Stormwater Management Ordinance
that requires new development to control water
- n-site
Bulk Regulations approved limiting the size of
structures, which limits the amount of impervious surface on a lot
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Incremental Village Actions
Received a grant to assist homeowners install flood
control devices (164 homes participated)
Northeast Parkway construction removed large portion
- f Business Park from combined sewer system
2010- Sewer User Fee created for infrastructure
repairs/maintenance and upgrades
Crawford Avenue will be disconnected from sewer
system
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Stormwater Management Plan
2007-the Ad-Hoc Sewer Committee
recommended and the Village Board approved the following motion:
“The creation of a Stormwater Management Plan
(SMP) that would handle a 10-year rain event (2.1”
- f rain per hour) with a goal of achieving such
protection in 10 years.”
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Area Communities’ Stormwater Management Planning Goals
Municipality Capacity Goal Cost Park Ridge 10-year storm $16 million Wilmette 10-year storm $35 million Skokie 10-year storm $80 million Evanston 10-year storm $200 million
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Stormwater Modeling
Computer Model of Sewer System
Topography Geographical Information Systems (GIS) Data Manhole Locations Pipe Sizes & Locations Design Storms
Two Main Components
Hydrologic Watershed characteristics, imperviousness, topography, etc. Hydraulic Sewer size, slope, material, etc.
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Modeling Process
The Village identified a three-phase process:
Phase I - Pass/fail analysis: after model is prepared
determine if the system can handle a 10-year rain event
Phase II – Calibrate the model, then identify system
bottlenecks that are potentially causing problems. Identify system improvements to bring the system to the 10-year protection
Phase III - Design and construct the improvements
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Stormwater Study Results
Phase I
Computer generated model of sewer system
indicates that the system fails, cannot handle a 10- year rain event
Phase II
Real data is used to update the computer model to
evaluate the system, surface storage and underground storage of stormwater are recommended
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Phase II Model Results
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Surface Storage
What is surface storage?
The use of the street to store stormwater during and after a storm for a
designated period of time
How does it work?
Berms (on the street) and restrictors (inside the sewer) are used to
control the amount of water that enters the sewer so that it does not fill up too quickly
Water is stored on the street while waiting to enter the sewer
How much water will be on my street?
Max ponding depth at the center of the road: 6 inches Max ponding depth at the curb: 9 inches Max ponding width on the road: Back of sidewalk Max ponding duration (after rain stops) for residential roads: 120
minutes
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Sub-Surface Restrictor in Catch Basin
Stormwater Enters Sewer from Curb Drain Inlet Storm water Enters the Catch Basin
Outlet Pipe to Combined Sewer Manhole
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Surface Storage
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The level of protection for the Village will be
increased from a 2-3 year level of protection to a 4-5 year
55% reduction in the number of homes at-risk for
flooding during a 10-year storm
Most cost effective means of large scale detention
Benefits of Surface Storage
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Cost for Surface Storage
The total cost for maximizing street storage is
approximately $5,592,060
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Conveyance and Detention
In order to obtain protection for the remaining areas at-
risk during a 10-year event additional storage methods must be used
Nine projects are recommended that include:
Detention ponds New storm sewers in various locations Enlarging existing combined sewers
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Conveyance and Detention Projects
Project #1- Three alternatives: Project #1.1 – Detention pond in Pohatan Park Project #1.2 – In-line storage Project #1.3 – Surface detention via detention storage Project #2 – 2,600 feet of 8 inch to 36 inch storm sewer and North ComEd
detention facility
Project #3 – 3,350 feet of 15 inch to 48 inch storm sewer and South ComEd
detention facility
Project #4 – 3,020 feet of 36 inch storm sewer Project #5 – 2,000 feet of 18 inch to 60 inch storm sewer to South North Shore
Channel Outlet
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Project #6 – 1,860 feet of 21 inch to 36 inch storm sewer and
Central ComEd detention facility
Project #7 – Upsize 750-foot section of existing combined
sewer to 24 inch to 36 inch sewer (this project has been eliminated by extending Project #2 to west of Cicero)
Project #8 – Upsize 1,000-foot section of combined sewer to
60 inch – 72 inch sewer
Conveyance and Detention Projects
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Conveyance and Detention Projects
Project #9 – Three alternatives were given consideration as
follows:
Project #9.1 – 11,400 feet of 24 inch to 60 inch storm
sewer to North (Touhy) North Shore Channel outlet
Project #9.2 – Rather than construct a new storm sewer
along Touhy to the North Shore Channel, direct storm runoff to in-line storage via twin 96 inch storm sewers under the abandoned Union Pacific ROW
Project #9.3 – Rather than construct a new storm sewer
along Touhy to the North Shore Channel, direct storm runoff to a detention pond along the abandoned Union Pacific ROW
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Recommended Conveyance and Detention Projects
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Engineer’s Project Priority Recommendations
Priority Project # Description Cost Homes Protected Cost per Home 1
Alternative 1 Flow restrictors & containment berms
5,592,060 $ 1,700 3,289 $ 2 5
New North Shore Chanel Storm Outlet
1,335,398 $ 210 6,359 $ 3 6
Storm sewer & ComEd Central detention pond
1,710,210 $ 152 11,251 $ 4 3
Storm sewer & ComEd South detention pond
2,843,679 $ 145 19,612 $ 5 9.3
8,000 feet of 24 inch to 60 inch storm sewer & abandoned Union Pacific ROW detention
9,427,386 $ 6 4
3,020 feet of 36 inch storm sewer
2,395,478 $ 7 2
Storm sewer & ComEd North detention pond
2,137,650 $ 44 48,583 $ 8 8
Upsize 1,000-foot section of combined sewer to 60 inch - 72 inch sewer along Pratt
1,933,168 $ 9 1.1
Storm sewer & Polatan Park detention pond
3,908,687 $ 10 1.3
Detention Storage (3 sites)
2,347,500 $ 11 7
Upsize 750-foot section of existing combined sewer to 24 inch to 36 inch sewer (Merged with Project #2)
33,631,216 $ Grand Total 345 34,269 $ 154 53,178 $
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$28,039,156 to implement the nine recommended
projects
Protection will be provided to the remaining 43%
- f the area still at-risk during a 10-year storm once
street storage is provided
Cost for Conveyance and Detention
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Summary of Improvements
Street Storage Only
152 berms and 3,981 hanging trap inlet restrictors Provides 4-5 year storm protection during 10-year storm Protection is provided to approximately 55% of the area Approximately $5,592,060
Conveyance and Detention
10-year level of protection for entire Village 9 projects which include storm water conveyance and detention Approximately $28,039,156
Total estimated cost for 10-year level of protection $33,631,216
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Ad Hoc Sewer Committee’s Recommendation
Ad Hoc Sewer Committee recommends to move forward with
street storage within 15-20% of the Village as a pilot program and that project #5-2,000 feet of 18 inch to 60 inch storm sewer to South North Shore Channel Outlet be advanced to 30% design state so that grant funding may be applied for the project
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Phase III Pilot Area
Recommended
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Funding Options
Low interest loans from the Illinois
Environmental Protection Agency (payable from the sewer user charge)
Grants Multi-year capital improvement program
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