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 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

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

Curb Inlets Not Restricted Restricted

Catch Basin Covers Restricted Unrestricted Approximately 70-75% of sewers are restricted within the Village

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

August 2, 2001 Flooding (35% response rate to survey)

September 13 & 14 2008 Flooding Storm estimated to be a 3.5 year event, data based on 134 phone calls received.

Sewage in Basement June 19, 2009 Storm Reports of Sewage in Basement 2-3 Year Event, 160 Phone Calls

Incremental Village Actions  2004  Adopted a Stormwater Management Ordinance that requires new development to control water on-site  Bulk Regulations approved limiting the size of structures, which limits the amount of impervious surface on a lot

Incremental Village Actions  Received a grant to assist homeowners install flood control devices (164 homes participated)  Northeast Parkway construction removed large portion of 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

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” of rain per hour) with a goal of achieving such protection in 10 years.”

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

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.

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

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

Phase II Model Results

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

Sub-Surface Restrictor in Catch Basin Storm water Enters the Catch Basin Stormwater Enters Sewer from Curb Drain Inlet Outlet Pipe to Combined Sewer Manhole

Surface Storage

Benefits of Surface Storage  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

Cost for Surface Storage  The total cost for maximizing street storage is approximately $5,592,060

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

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

Conveyance and Detention Projects  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  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

Recommended Conveyance and Detention Projects

Engineer’s Project Priority Recommendations Homes Cost per Cost Description Priority Project # Protected Home Alternative Flow restrictors & containment berms 1 $ 5,592,060 1,700 $ 3,289 1 2 5 New North Shore Chanel Storm Outlet $ 1,335,398 210 $ 6,359 Storm sewer & ComEd Central detention 3 6 $ 1,710,210 152 $ 11,251 pond Storm sewer & ComEd South detention 4 3 $ 2,843,679 145 $ 19,612 pond 8,000 feet of 24 inch to 60 inch storm 5 9.3 sewer & abandoned Union Pacific ROW $ 9,427,386 detention 345 $ 34,269 3,020 feet of 36 inch storm sewer 6 4 $ 2,395,478 Storm sewer & ComEd North detention 7 2 $ 2,137,650 44 $ 48,583 pond Upsize 1,000-foot section of combined 8 8 sewer to 60 inch - 72 inch sewer along $ 1,933,168 Pratt Storm sewer & Polatan Park detention 154 $ 53,178 9 1.1 $ 3,908,687 pond 10 1.3 Detention Storage (3 sites) $ 2,347,500 Upsize 750-foot section of existing 11 7 combined sewer to 24 inch to 36 inch sewer (Merged with Project #2) Grand Total $ 33,631,216

Cost for Conveyance and Detention  $28,039,156 to implement the nine recommended projects  Protection will be provided to the remaining 43% of the area still at-risk during a 10-year storm once street storage is provided

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

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

Recommended Phase III Pilot Area

Funding Options  Low interest loans from the Illinois Environmental Protection Agency (payable from the sewer user charge)  Grants  Multi-year capital improvement program

Questions?