millbrook dam environmental assessment study dan marinigh cao/secretary-treasurer otonabee region...

Millbrook Dam Environmental Assessment Study

Dan MarinighCAO/Secretary-Treasurer

Otonabee Region Conservation AuthorityOctober 20, 2015

Otonabee Conservation …. providing leadership to achieve healthy watersheds

Objectives for Today

• Recap the history of the project• Provide an update of the more recent work• Seek your input


Why an EA Study

• The Millbrook Dam– 120-metre long earth-filled embankment dam

constructed in the early 1800’s– The dam suffers from issues and problems common of

dams of this age– Hazard potential classification is “high”– The existing overflow weir and spillway are incapable of

discharging flood flows and the dam is inadequate to prevent toppling and/or sliding

– Dam failure could result in loss of life, property damage, environmental harm and economic and social disruption


Purpose of the EA study

To identify, evaluate and investigate a reasonable range of options to resolve the

problem of incremental flooding caused by the potential failure of the dam


The EA Study

• Launched in 2012 – draft completed in late 2013• Evaluated a range of options and subject to public

consultation• Recommended preferred option:

– Removal of existing 7 m wide weir and spillway and replaced with a new, 36 m stepped weir capable of passing 100 m3/second

– Crest height of new weir would be 0.5 m lower than the crest height of the present weir

– Headpond would be excavated to natural depth– Earthen embankment would be strengthened and made

impermeable.


The EA Study

• The EA Study Report was presented to the ORCA Board in November 2013.

• The Board deferred a decision on the approval of the EA Study, primarily because it needed to better understand the financial implications of the recommended preferred option

• ORCA continues to consider the EA Study report to be a draft report


Meanwhile

• The province adopts new dam safety guidelines – came into effect April 1, 2013

• ORCA commissions a review of its earlier dam safety assessment for the Millbrook Dam to ensure that it will satisfy the new dam safety guidelines

• The review identifies some issues with the “inflow design flood” value, a key value that determines the design criteria to be met when contemplating a new dam or repairs to an existing dam


Challenges

Before moving forward ORCA had to find solutions to two key issues:

1. How to pay for the project2. Understanding the significance of a new “inflow

design flood” value and its implication to the draft EA study.


Solutions to The Challenges

How to Pay for the Project:– In April the ORCA Board adopted a policy on the

management of water and ice control structures.– The policy identifies how ORCA will pay for major

repairs and replacements of its portfolio of water & ice control structures.

– ORCA received a provincial and federal grants under the Small Communities Fund for $2.238 million


Solutions to The Challenges

Inflow Design Flood Value:– ORCA has entire dam safety assessment re-done;

all previous work is reviewed, input values are validated and documented and all analysis is brought together into one standalone report

– Analysis undergoes a peer review process – Review finds that the “inflow design flood”

changes from 100 m3/second to 181 m3/second– Review completed in January 2015 – ORCA Board

adopts the findings


Moving Forward

• The goal for moving forward is to achieve the following outcomes:– To ensure that the requirements of the Class EA

process for revising the EA study and selecting the preferred solution are met.

– That the preferred solution must meet the design criteria established under the Lakes and Rivers Improvement Act so that it may ultimately be approved for construction.


Approach for Moving Forward

Step 1:– Investigate, evaluate and select a structural

solution that retains the head pond, safely passes the “inflow design flood” value and mitigates issues with the earthen embankment (new way to implement the preferred option)

– Review and update cost estimates for the new preferred option and the previous options A & B

– Consult on the revised preferred option


Approach for Moving Forward

Step 2:– Update evaluation of environmental effects – Obtain Board approval for the revised EA Study

Report

Step 3:– Undertake mandatory Notice of Filing of an

Addendum and Filing of Project Approval


May Jan2016

Jul Sept Oct Nov DecAugJun

Retain Consultant

1st Public Info Session

Investigate/ Evaluate & Select Design Alternative & Update Cost Estimates

Public Review of Design & Updated Cost Estimates

Notice of Filing an Addendum

Update Environmental Effects Evaluation

Notice of Project Approval

May 15- Jul 6

Jun 10

Jul 6- Sept 18

Oct 15- Nov 16

Nov 16

Jan 15- Feb 15

Mar 15

Proposed Millbrook Dam EA Process & Timeline

Feb MarApr 2015

CLC Meeting

CLC Meeting

Board Decision to Proceed Apr 16

Board Adoption of Revised EA Study ReportDec 17

Progress to Date

Public Engagement:– June 10 Information Session– Updated materials on ORCA website– Letter updating parties on mailing list– Letter updating Aboriginal communities and organizations– Newspaper ads for the today’s Public Information Centre

Funding:– Announcement of SCF grant for $2.238 million– Special benefiting capital levy to be included in 2016 proposed budget

Revision to EA Study:– Retained HATCH to identify a new structural solution for option C,

update costs and prepare documentation for addendum


Next Steps

October – November:– Today’s Public information Center– 30 day comment period– Consider public input and update evaluation of environmental effects

December:– Meet with Community Liaison Committee– Board decision on proposed Addendum

January – February:– Issue Notice of Filing an Addendum– 30 day comment period

March:– Issue Notice of Project Approval– Issue tender for design and construction project management


millbrook dam environmental assessment study dan marinigh cao/secretary-treasurer otonabee region...

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