little walnut creek – jamestown tributary stream
TRANSCRIPT
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Little Walnut Creek – Jamestown Tributary Stream Rehabilitation: 60% Design Update
Michelle Adlong & Rupali SabnisNACA Presentation
April 19, 2018
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WATERSHED PROTECTION DEPARTMENT MISSIONS
ErosionFloodingWater Qualityimprove reduce hazards of reduce hazards of
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WATERSHED PROTECTION DEPARTMENT MISSIONS
ErosionFloodingreduce hazards of reduce hazards of
• Erosion and flooding locations tracked: neighbors call 311 or from city staff
• WPD builds projects where there are clusters of high priority problems
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PROJECT LOCATION
Construction area
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Erosion• 19 active erosion sites
due to eroding banks• Threatened resources
are public and private infrastructure:
– Multifamily buildings & parking lots
– Yards, fences– Culverts, sidewalks– Utility poles, pipes
PROBLEM SUMMARY
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Erosion• 19 active erosion sites
due to eroding banks• Threatened resources
are public and private infrastructure:
– Multifamily buildings & parking lots
– Yards, fences– Culverts, sidewalks– Utility poles, pipes
PROBLEM SUMMARY
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Erosion• 19 active erosion sites
due to eroding banks• Threatened resources
are public and private infrastructure:
– Multifamily buildings & parking lots
– Yards, fences– Culverts, sidewalks– Utility poles, pipes
PROBLEM SUMMARY
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Flooding• Known local flooding
problems• Some buildings in the
floodplain• Roadways that cross
the creek are frequently flooded
PROBLEM SUMMARY
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• Stabilize an eroding 2,800 LF reach of the Jamestown Tributary between Thurmond St. and its confluence with Little Walnut Creek
• Reduce risk of flooding to residents along Jamestown Drive
• Reduce frequent roadway overtopping at Fairfield Drive
• Model the tributary’s floodplain
INTEGRATED PROJECT OBJECTIVES
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PROPOSED PROJECT ELEMENTS: CHANNEL STABILIZATION
Erosion protection will use: restoration with native plants and channel bank armoring with boulder walls and bank sloping
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PROPOSED PROJECT ELEMENTS: CHANNEL STABILIZATION
Restoration with Native Plants
Example project - before
Example project - after
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PROPOSED PROJECT ELEMENTS: CHANNEL STABILIZATION
Restoration with Native Plants
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PROPOSED PROJECT ELEMENTS: CHANNEL STABILIZATION
Stabilization with vertical boulder wall
Example project - before
Example project - after
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Stabilization with vertical boulder wall
PROPOSED PROJECT ELEMENTS: CHANNEL STABILIZATION
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PROPOSED PROJECT ELEMENTS: CHANNEL STABILIZATION
Stabilization with bank benching
Example project - afterExample project - before Example project - after
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PROPOSED PROJECT ELEMENTS: CHANNEL STABILIZATION
Stabilization with bank benching
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Downstream of Fairfield Drive: Existing
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Downstream of Fairfield Drive: Proposed (Photosimulation)
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• Culvert will be replaced with 46’ long bridge.
• Will reduce frequency and depth of flooding over Fairfield Drive
• Bridge will still be subject to flooding in major storms
PROPOSED PROJECT ELEMENTS – FAIRFIELD CROSSING
Looking downstream toward Fairfield Drive
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FAIRFIELD CROSSING – EXAMPLE BRIDGE
Example project – similar type but longer bridge Looking downstream toward Fairfield Drive
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FLOODPLAIN
• This project created an engineering model for the tributary. This better maps the existing floodplain.
• The anticipated post-project flood hazard is reduced, primarily around Fairfield Drive
• We recommend you consider flood insurance if you are near the floodplain or if you have flooded in the past
City of Austin Floodplain [email protected]
512-974-2843
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• What is localized flooding -Flooding that occurs away from the creek due to insufficient or lack of storm drain system
• 5,884 Total complaints
• No quick or easy solution
1,995 Buildings 2,409 Yards 1,480 Streets
LOCALIZED FLOODING CITYWIDE
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• Known local flooding problem in the area– Historical complaints– Feedback during last meeting– Postcard feedback
• Adding on already proposed erosion project • Lays ground work for future projects• Addresses some of the local flooding issues in the area, but
not all
PROPOSED PROJECT – LOCALIZED FLOODING
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WHAT IS A STORM DRAIN SYSTEM?
• System of streets, ditches, pipes and culverts
• Drains rainfall from streets to nearby creek
• Inlets are placed along curb to catch rainfall
• Streets should drain in most storms.
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COMPONENTS OF A STORM DRAIN SYSTEM
1. Inlets and curbs capture rain water
2. Underground pipes carry the water
3. Rain water is released into a creek atthe outfall. Sometimes it goes to awater quality or detention pond first
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PROPOSED STORMDRAIN IMPROVEMENTS Improvements to three systems along Jamestown
Drive – Systems B, D, E Addition of new outfall near Alden Drive –
System C New system at Bangor Bend Drive – System A All improvements designed to accommodate
future extension of the systems Local flood risk reduction for several properties
along Jamestown Dr
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SYSTEM A
10 ft curb inlet
10 ft curb inlet
20 ft curb inlet
5ft x 2ft box pipe
Connect to existing culvert at Bangor Bend
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SYSTEMS B, C, D, AND E Upgrades to existing systems B, D, and E New system C to take flows from Alden Several new inlets proposed Existing inlets to remain and connect to
proposed improved systems
42 inch pipe
4ft x 2ft box pipe
36 inch pipe
Existing 48 inch pipe to remain functional
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• An easement is a part of a property wherethe City has limited rights of access and/oruse. Land is still owned by owner.
• Drainage easement purpose - For the flow of storm water and to access and maintain drainage infrastructure.
• Easements should be maintained as grass or flowers
• Both permanent drainage easements and temporary work space easements will be needed in order to construct the project.
• Owners will be notified by mail and will work with Office of Real Estate Services.
EASEMENTS
Example Drainage Easements
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MOVING FORWARD
• There will be another neighborhood meeting before construction
Project KickoffSummer 2015
Preliminary EngineeringSpring 2016
30% Design
Summer 2017
60% Design& Neighborhood
MeetingSpring 2018
90% Design Fall 2018
ConstructionLate 2019-2021
Final Design, Permitting, Contracting
2019
Landscape Establishment
2021+
Estimated project schedule
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SUMMARY AND CONCLUSION
• These proposed improvements will:
– Protect property from eroding sections of streambank along the Jamestown Tributary between Thurmond St. and Payton Gin Pocket Park
– Reduce risk of localized flooding along Jamestown Drive
– Reduce frequent roadway overtopping at Fairfield Drive
• Total estimated project cost – $8 million
• Anticipated start of construction early 2020
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Michelle Adlong, P.E.Watershed Protection Department, City of AustinP: (512) 974-2826
Rupali Sabnis, P.E., CFMWatershed Protection Department, City of AustinP: (512) 974-3375