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