Breaching the Mahar Regional School Dam Presentation to Ralph
C. Mahar Regional School Committee GZA GeoEnvironmental, Inc.
February 9, 2011
Slide 2
Presentation Outline Introductions Derek Schipper, P.E. and
Greg Hunt GZA GeoEnvironmental, Inc., Norwood, MA Existing Site
Information Project Background Summary of Dam Breach Feasibility
Study Proposed Dam Breach Design Permitting & Construction
Preliminary Cost Estimate Timeline Example Project Questions
Slide 3
Existing Site
Slide 4
Existing Dam Pond / Impoundment Dam Spillway & Low- level
Outlet with Culvert through Dam Concrete Core Wall Around
Spillway
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Dam Information Mahar Regional School Dam: Dam Size: Small
Hazard Rating: Significant Condition: Poor Main Deficiencies:
Growth of trees throughout dam Erosion on top of dam and near
waterline Embankment seepage
Slide 6
Project Background 1950s: Dam constructed 1960: Dam repaired
following spillway damage 2005: New MA Dam Safety Regulations go
into effect 2008: DCR Office of Dam Safety (DCR/ODS) ordered that
dam be inspected by professional engineer July 2009: GZA performed
Phase I Inspection/ Evaluation of Dam; found dam to be in Poor
condition Sept. 2009: School District ordered by DCR/ODS to repair,
breach, or remove dam by March 11, 2011and continue to have dam
inspected every 6 months.
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Project Background (Cont.) 2009 present: GZA has performed
three 6-month inspections, dam found to be in similar condition
2010: School Committee approves plan to address condition of dam
through dam removal/breach 2010: GZA prepares Dam Breach
Feasibility Study to evaluate potential dam breach
Slide 8
Dam Breach Feasibility Study GZA Scope of Work: Extension
request from DCR/ODS (11/30/2012 New Date) Field Work Site Survey,
Wetland Resource Evaluation, Sediment Analysis Technical Analysis
Hydrologic & Hydraulic Modeling, Conceptual Breach Design
Permitting Investigation Estimate of project impacts and required
local, state, and federal permits Cost Estimate & Funding
Sources Cost estimate to perform dam breach & potential
grants
Proposed Conditions Conceptual Design Restored Gulf Brook
Stream Channel Excavated Section of Dam for Breach Channel Concrete
Core Wall to Remain Below Ground Stone Erosion Protection Grassed
Slopes
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Permitting & Construction Environmental Permitting:
Numerous Local, State, and Federal permits required to work in
wetland resource areas Permit process will likely lasts 9 months 1
year Final Design and Specifications: Prepare final design plans
and specifications suitable for contractor bidding and construction
Construction: Once Final Design is complete and permits are in
place, work awarded to Contractor to perform breach work
Construction to take about 4 weeks
Slide 13
Preliminary Cost Estimate Permitting & Final Design
Engineering $ 85,000 Construction Work$ 170,000 Construction
Contingency (25%)$ 43,000 Construction Engineering (5 weeks)$
35,000 Total Estimated Cost$ 333,000
Slide 14
Preliminary Timeline Spring 2011: Submit Environmental
Permitting Summer 2011: Final Engineering Design &
Specifications Spring 2012: Award Construction Contract Summer
2012: Perform Dam Breach Work Fall 2012 - 2013: Revegetation
Monitoring & Maintenance by Contractor Note: Under current
timeline, dam breach work must be completed by November 30, 2012,
and Six-Month Follow-Up Inspections of Dam must continue until work
is completed.
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Questions?
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Before Dam Breach One Year After Dam Breach Example Project:
Champlin Pond Dam Breach
