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Upper Malletts CreekStormwater Conveyance StudyProject UpdateMay 21, 2013
Meeting Purpose
•Update on study progress
•Gather public feedback
Items to Review and Discuss•Analysis
▫Review website & data collection▫Storm sewer inspection & cleaning ▫Soil boring information▫Storm drain inlet capacity analysis
•March 15 storm event modeling•Potential stormwater management solutions•Discussion•Next step – create flood management
alternatives
Project Goals
•Reduce probability of flooding by improving stormwater management
•Identify cost of implementation per level of service
•Do not adversely impact downstream interests
•Maintain and/or enhance water quality •Long term sustainability
Review of Data Collection
•Website▫Online at www.uppermallettsstudy.org
•Online Flood Reporting Tool•On-site interviews
▫To date have met with 14 homeowners, progressing with additional meetings
▫Information used to improve model results
Storm Sewer Inspection & Cleaning•Completed for
over 65,000 feet of the system, 100%
•System generally in good working order
•Minor deterioration and sediment deposits
Soil Boring Information
•Twelve borings taken within project boundary
•Most soil was firm clay•Groundwater
observations generally between 5’ and 15’
•Long term groundwater modeling at two points
Storm Drain Grate Capacity Analysis
•Completed inspections of 200 storm drains to determine type, size, and condition
•Three areas don’t have inlet capacity to handle larger storms.▫Hanover between Waverly & Winsted▫Scio Church between 7th & Main▫Within Lawton Elementary playground
•Relatively easy fix with immediate results, some areas currently being improved
Storm Event Modeling
•Modeling is iterative process▫Combine model output with site observation
and make adjustments ▫Ultimately will help determine benefits and
level of service •Preliminary modeling of March 15, 2012
event▫Shows flooding in many areas where actual
flooding occurred▫Does not show flooding in all areas
Detention Site Screening•Engineering field review
of 22 areas to determine suitability
•Evaluate several factors for comparison▫Property type &
ownership▫Current land use▫Relative elevation▫Outlet suitability▫General analysis
Detention Site Considerations• Potential areas for improvement to existing
detention (additional volume)▫Ann Arbor Ice Cube (Pittsfield Twp.)▫Meadowinds Detention Pond (Pittsfield Twp.)▫Cardinal Homes Detention Basin▫Lans Lake▫Lans Basin
• Potential areas for new surface detention▫Churchill Downs▫Las Vegas Park▫Ann Arbor Schools – Pioneer HS
• Potential areas for underground detention▫Lawton Park
Ann Arbor Ice CubeArea (ac)
0.70
OwnershipPrvt,
Commercial
Volume (cu ft)90,000
Benefit Potential
Expected Cost
Meadowinds BasinArea (ac)
1.16
OwnershipPrvt, HOA
Volume (cu ft)50,000
Benefit Potential
Expected Cost
Cardinal Homes Detention Basin
Area (ac)0.83
OwnershipPrvt, HOA
Volume (cu ft)70,000
Benefit Potential
Expected Cost
Lans LakeArea (ac)
4.37
OwnershipPrvt, HOA
Volume (cu ft)475,000
Benefit Potential
Expected Cost
Lans BasinArea (ac)
1.86
OwnershipPrvt, HOA
Volume (cu ft)200,000
Benefit Potential
Expected Cost
Churchill Downs ParkArea (ac)
2.25
OwnershipPublic, City
Volume (cu ft)630,000
Benefit Potential
Expected Cost
Las Vegas ParkArea (ac)
0.18
OwnershipPublic, City
Volume (cu ft)4,000
Benefit Potential
Expected Cost
Pioneer HS (West of 7th)Area (ac)
0.60
OwnershipPrvt, AA Schools
Volume (cu ft)80,000
Benefit Potential
Expected Cost
Pioneer HS (East of 7th)Area (ac)
0.88
OwnershipPrvt, AA Schools
Volume (cu ft)40,000
Benefit Potential
Expected Cost
Lawton ParkArea (ac)
2.61
OwnershipPublic, City
Volume (cu ft)825,000
Benefit Potential
Expected Cost
Additional Management Considerations
• Potential areas for storm sewer improvements▫Scio Church Road-pipe storage▫Chaucer/Ascot/Lans-size increase▫Hanover/Dogwood-size increase▫Wiltshire/Churchill/Delaware-relief sewer▫Mershon–size increase
• Green techniques▫Porous pavement for select road
reconstructions and private parking lots▫Road diets to reduce impervious area▫Rain gardens at surface detention areas & rear
yards - private
Potential Detention VolumesAreas Within City Boundary
NameArea (ac)
Depth (ft) Ownership Volume (ft3)
Volume (ac-ft)
Benefit Potential
Expected Cost Potential Area
Lawton Park 2.62 7.25 public, City of AA 825,000 18.9 High High 114,000 sqft
Churchill Downs Park 2.23 6.50 public, City of AA 630,000 14.5 High Medium 97,000 sqft
Lans Lake 4.36 2.50 private, HOA 475,000 10.9 High Medium 190,000 sqft
Lans Basin 1.86 2.50 private, HOA 200,000 4.6 Medium High 81,000 sqft
Pioneer HS (W of 7th) 0.60 3.00 private, AA Schools 80,000 1.8 Low Low 26,000 sqft
Pioneer HS (E of 7th) 0.87 1.00 private, AA Schools 40,000 0.9 Low Low 38,000 sqft
Cardinal Homes 0.83 2.00 private, Condo Assoc. 70,000 1.6 Low Medium 36,000 sqft
Las Vegas 0.18 0.50 public, City of AA 4,000 0.1 Low Low 8,000 sqft
Subtotal Potential Volume 2,324,000 53.4
Areas Outside of City Boundary
Ice Cube 0.37 5.50 private, commercial 90,000 2.1 Medium Low 16,000 sqft
Meadowinds Basin 1.17 1.00 private, HOA 50,000 1.1 Low Low 51,000 sqft
Subtotal Potential Volume 140,000 3.2
Total Potential Volume within Watershed 2,464,000 56.6
Discussion
Next Steps •Develop comprehensive stormwater
management alternatives▫Combination of many ideas/management
techniques and tools▫Cost/benefit considerations will be a factor▫Funding potential will be a consideration
•Citizens Advisory Group meeting•Public informational meeting
Gather Information
Public Engagement
Upper Malletts Creek Stormwater Conveyance Study TimelineP
roje
ct A
ward
Jan
uary
2013
Ap
ril
201
3
Preliminary Alternatives Analysis &
Memo
Draft Study Report
Final Study Report
Finalized Alternativ
es Analysis &
Memo
July
2013
Dece
mb
er
201
3
Jan
uary
2014
Feb
ruary
2014
Marc
h 2
013
Data Collection, Monitoring, &
Modeling
Feb
ruary
2013
Sep
tem
ber
201
3
Upper Malletts CreekStormwater Conveyance StudyProject UpdateMay 21, 2013