Upper Malletts CreekStormwater Conveyance StudyProject UpdateMarch 14, 2013

Items to Review and Discuss

•Review of study area•Stormwater management approaches •Project timeline•Information collected to date •Public input•Discussion•Next steps

Engineering Parameters

•Reduce probability of flooding by enhancing management of stormwater

•Identify cost of implementation per level of service

•Do not adversely impact downstream interests

•Maintain and/or enhance water quality •Long term sustainability

Stormwater Management Approaches•Catchbasin enhancements•Street maintenance•Clean/repair existing drainage infrastructure •Enhance/modify existing detention facilities•Overland stormwater flow management•Construct new surface stormwater detention •Construct new underground stormwater

detention •Upsize/enhance storm sewer capacity•Bio-retention/rain gardens

Catchbasin Enhancements

•Evaluate impact of installing additional catchbasins▫What is the design

capacity of grates?▫Is existing capacity

sufficient?▫Will additional

catchbasins provide significant improvements?

Street Maintenance

•Street sweeping•Clean inlet grates•23,000 catchbasins in City

Clean/Repair Existing Storm Drains

• Identify adequacy of existing storm drains▫Does modeling show drains

to be adequate? ▫Do public comments

suggest problem with drain?

•Complete targeted inspections of storm drains to establish locations for repairs and maintenance

Enhance Existing Detention • Review feasibility to

enhance existing detention▫ Is site acceptable? ▫Do modeling results

show benefit? • Evaluate increasing

capacity of basins and ponds▫Sediment removal▫Lowering of water levels▫ Increase surface area

Overland Flow Management •Evaluate changing ground

and street elevations to enhance overland flow▫Map and model ▫Review pictures and

comments▫Complete on sites reviews▫Can overland flow be

better managed?

New Surface Detention

•Evaluate construction of new surface detention facilities ▫Where is there

space to build?▫Will significant

impacts be realized?

▫Is this space cost beneficial for detention?

Storm SewerEnhancements•Evaluate installation

of new or larger storm drains▫Modeling and

analysis of storm drain system

▫What is adequate level of service?

▫Where are optimal and cost effective locations?

Underground Detention•Identify need for underground detention

▫Is adequate space for surface detention available?

▫Is underground detention affordable?▫What are groundwater impacts?

Bio-retention or Rain Gardens•Evaluate using in

conjunction with other management practices

Stormwater Management Recommendation

•Combination of these management practices

•Other practices may be added •Cost/benefit considerations will be a

factor•Recommendations must be authorized in

City capital improvement plan and funding secured

•Looking for grant assistance

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

Information Collected to Date •Infrastructure records/GIS layers •Model of the City's stormwater

infrastructure •Past studies and study area maps •Record of homes where FDD has occurred•Past soil boring data •LIDAR information for this area •Rainfall records from the March 15 2012

storm •Records/complaints of known flooding

Public Input and Engagement

•Public informational meetings▫Each 4 to 6 weeks

•Citizens advisory meetings▫Each 4 to 6 weeks

•Website▫Online at www.uppermallettsstudy.org

•Online Flood Reporting Tool

Discussion

Next Steps •On-line data collection and web updates•On-site interviews and data collection •Catchbasin grate capacity •March 15 storm event modeling•Soil boring location evaluation•Screening of management approaches•Citizens Advisory Group meeting•Public informational meeting

▫4 to 6 weeks

Upper Malletts CreekStormwater Conveyance StudyProject UpdateMarch 14, 2013