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Allen Creek Railroad Berm Opening Feasibility Study

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(a2gov.org/AllenCreekBermStudy)

Project Update
The final public meeting for the Allen Creek Railroad Berm Opening Feasibility Study was held on Wednesday, December 4, 2013.

Click here for the study recommendations final report (PDF- 20.7 MB)

 

Project Objective

Explore options to install a hydraulic relief through the berm located between Depot St. and the Huron River to allow floodwaters to discharge more efficiently to the river, thereby reducing frequency and severity of flooding in the area. Examine the costs of adding a below-grade viaduct to double as a pedestrian access point and emergency flood discharge point.  Develop a Benefit-Cost analysis to demonstrate whether the potential reduction in flood damages would exceed the cost of the project.  If so, the City may be eligible to receive Pre-Disaster Mitigation Funding from FEMA to implement the project.


Study Area
Allen Creek Railroad Berm Opening Feasibility Study Area

Background

The railroad berm near the mouth of Allen Creek is oriented perpendicular to the overland flow and causes the floodplain depth to be as deep as 10 feet.  Upstream of the influence of this berm flood depths are more typically in the 3 to 5 foot range. In March of 2007 the City of Ann Arbor adopted a Flood Mitigation Plan; the plan includes 56 specific mitigation objectives or recommendations.  One of the objectives (Mitigation Objective Project 51) recommended a study of the Allen Creek railroad berm.  The full Flood Mitigation Plan can be viewed at www.a2gov.org/floodplains.

Study and Recommendations

Orchard, Hiltz & McCliment, Inc. (OHM) has been selected to perform the necessary tasks to determine the feasibility of opening up the railroad berm near the mouth of Allen Creek and compare the project cost to the decreased cost associated with the lowered risk to the structures currently in the floodplain.  Federal Emergency Management Agency (FEMA) Benefit-Cost Analysis (BCA) software will be used to determine the potential of a FEMA Pre-Disaster Mitigation Grant Program fundable project.

As a secondary effort, Orchard, Hiltz & McCliment, Inc. will determine the feasibility of providing a shared-use non-motorized path through the railroad berm from the Main Street/Depot Street area to the Huron River.  Opening the berm for flow conveyance may provide the opportunity to accomplish this connection. Final study recommendations will address feasibility, costs, and potential reduced flood risk benefits of a project.

 

Floodplain 

 

Project Schedule

December 19, 2012

 Project Kickoff

December –
February 2013

 Task 1: Information Gathering

  • Review topographic, utility, and InfoSWMM model data
  • Review the existing HEC-RAS model for information on floodplain geometrics and flow conveyance
  • Review April 2012 Flood Insurance Study
  • Survey first-floor elevations
  • Meet with property owners that may impact, or be impacted by, proposed hydraulic improvements along the berm
February – March 2013

Task 2: Option Development

  • Develop four alternatives to provide hydraulic relief
  • Develop planning level cost estimates for each alternative
  • Meet with TAC to discuss options
March 2013

 Task 3: Option Analysis and Stakeholder Engagement

  • Public Meeting #1 - 3/13/13 View the presentation (PDF - 6MB)
  • Narrow the options to a preferred alternative, based on discussions with railroad, impacted property owners, City staff, the TAC, and other stakeholders
  • Determine future operation and maintenance costs
April – June 2013

 Task 4: Conceptual Design Development

  • Develop a set of concept drawings to illustrate the project
  • Provide cost estimated to implement the preferred option, as well as anticipated life-cycle maintenance costs
  • Identify additional funding options for the preferred option
July - December 2013

 Task 5: Benefit-Cost Analysis

  • Perform a Benefit Cost Analysis (BCA) for the preferred option using FEMA's BCA software. This analysis will be performed for the 20%, 10%, 2%, 1%, and 0.2% annual chance flood events
  • Prepare a Final Report which summarizes the modeling effort, stakeholder coordination, alternatives analysis, planning-level cost estimates, and the results from the BCA tool
  • Final Public Meeting to discuss findings - 12/04/13  View the presentation (PDF - 37MB)

 

Updated December 18, 2013