INDIAN BROOK RESERVOIR DAM REHABILITATION

NYSDEC Dam Safety Design Criteria and Ensuring A Sustainable Water Supply

September 19, 2018

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Today’s Presenters

24 September 2018

2

Certified Project Manager and Construction Engineer for the IBRD Rehabilitation855 Route 146 Clifton Park, NY 12065518 250 7304michael.kosier@arcadis.com

MIKE KOSIER, PEAssociate Vice President

Principal in Charge for the Village of Ossining

CAROLYN LOWE, PEVice President

44 South Broadway White Plains, NY 10602914 641 2725carolyn.lowe@arcadis.com

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Agenda

324 September 2018

• Learning Objectives (2 minutes)• The Basics (Dam Types, Terminology,

Purposes, Owner Responsibilities) (7 minutes)

• Dam Conditions and Failures (3 minutes)

• New York State Dam Safety Regulations (3 minutes)

• Case Study – Village of Ossining IBRD (10 minutes)

• Q&A – (5 minutes)

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Learning Objectives• Identify various types of dams, their functions and their hazard

classifications

• Understand how dams can fail

• Explain why dam regulations came into effect

• Describe some of the NYS DEC Dam Safety Requirements

• Apply dam safety design criteria to an existing Class C, High Hazard earthen dam through the use of a case study

The BasicsDam Types, Terminology, Purposes, Owner Responsibilities

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What is a Dam?Definition: An artificial barrier and appurtenant structures constructed for the purpose of storing water.

In NYS a permit is required to construct and operate a dam if: • It is at least 10 feet high.• Or it stores 1 million gallons or more (3.07 acre feet)• Or it has a drainage area of 1 square mile.

Note: Height and impoundment measured at top of dam

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Example Dam Types• Earthen / Embankment

• Masonry Gravity

• Concrete Gravity

• Concrete Arch

• Composite

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Earthen / Embankment Dam

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Typical Earthen Dam Cross Section

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Dam Components and Terminology

Embankment

Toe

Chute

Spillway

Stilling Basin

Impoundment

Abut

men

tAbut

men

t

Groin

CrestWave Protection

Indian Brook Reservoir Dam

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Dams in the U.S.• National Inventory of Dams ~90,580 Dams

• Dams as Part of our Nation’s Infrastructure:

- Water Supply (9.4%) - Tailings (9.4%)

- Flood Control (15.6%) - Irrigation (9.6%)

- Hydropower (3.0%) - Fire & Farm Ponds (13.7%)

- Navigation (0.3%) - Other Purposes (5.2%)

- Recreation (33.8%)

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Owner Responsibilities

• Inspection

• Maintenance & Repair

• Operation

• Monitoring

• Emergency Action

Dam safety programs oversee owner to protect downstream lives, property, and natural resources

Dam Conditions and Failures

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Condition of DamsU.S. Dams Received a "D" for "Poor" on ASCE’s 2017 Report Card for America’s Infrastructure

NYS Dams Received a “C-” in ASCE’s 2015 Report Card

• $152 Million Needed in NY State for the Rehabilitation of High and Intermediate Hazard Dams

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Principle Modes of Dam Failures

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Failures Have Lead to Dam Regulations• 1929 - CA enacts first dedicated dam safety

regulations - Following 1928 St Francis Dam Failure

• 1970’s failures lead to public concern over dam safety (178 people died & $1 billion estimated damages)

• 1970s to early 1980s dam inventory & inspections

• State Regulatory Programs

o ~ ½ by end of 1970so ~ ½ by end of 1980s o DE (2005) & AL (2006+)

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Regulatory AgenciesFederally Regulated Dams

• US Bureau of Reclamation

• US Army Corps of Engineers

• Federal Energy Regulatory Commission

• Unites States Department of Agriculture

Non-Federal Dams

• Federal Emergency Management Association (Administer the National Dam Safety Program)

• State Dam Safety Programs

New York State Dam Safety Regulations

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NY State Dam Safety Program

• NY dam safety provisions derive from the Conservation Law of 1911 (then 1985 Guidelines for Design of Dams - Revised 1989)

• Technical review of proposed work• Regulatory inspection by DEC engineers• Enforcement (repair or removal of unsafe dams)• Emergency planning and response• Bond Act Dam Safety Funding

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Dam Classification and Owner Responsibility

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How to Determine Hazard Classification?• Dam Break Analysis

• Develop Inundation Limits & Flood Velocities in Downstream Drainageway

– Class A: Damage to isolated farm buildings, undeveloped lands, country roads

– Class B: Damage to homes, main highway, public utilities– Class C: Potential for loss of life, serious damage to homes,

commercial buildings, etc.

• Hazard Classification Can Change!

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A Hazard Dam Owner Responsibility• Operate and maintain a safe dam

• Prepare and implement an Operation & Maintenance Plan

• Record property transactions for parcel containing the dam

• Conduct Hazard Class verification by a PE every 10 yrs

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B Hazard Dam Owner Responsibility• Operate and maintain a safe dam• Prepare and implement an Operation & Maintenance Plan• Record property transactions for parcel containing dam• Conduct an inspection by PE every 4 yrs• Conduct an engineering assessment by PE every 10 yrs• Prepare an Emergency Action Plan and conduct exercises• Report flow in auxiliary spillway• Submit annual certification

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C Hazard Dam Owner Responsibility• Operate and maintain a safe dam

• Prepare and implement an Operation & Maintenance Plan

• Record property transactions for parcel containing dam

• Conduct an inspection by PE every 2 yrs

• Conduct an engineering assessment by PE every 10 yrs

• Prepare an Emergency Action Plan and conduct exercises

• Report flow in auxiliary spillway

• Submit annual certification

• Demonstrate financial assurance for life of dam

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Actions for Dam Repair / RehabilitationPermits are required for work on all dams in NYS unless:

• Less than 15 feet high and 3 million gallons

• Less than 6 ft high regardless of impoundment

• Less than 1 million gallons regardless of height

Case Study – Indian Brook Reservoir Dam (IBRD) Rehabilitation

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About the IBRD• Built in 1889 to provide water storage for the Village

• Earthen embankment dam with a concrete/masonry core wall

• Improved in 1909, nothing significant since

• Maximum height 34 ft

• Maximum storage 365 acre-ft (119 mil gal)

• High Hazard, Class C• Minor flooding of two residential structures• Damage to the Croton Aqueduct and Quaker Bridge Road• Significant flooding and probable loss of life at the WTP

(staffed 24/7)

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Site Aerial – Before

Crest

Embankment

Toe

Chute

Spillway

Gate House

Stilling Basin

WTP

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Project History• NYCRR Part 673 Dam Safety Regulations revised in

August of 2009• April 30, 2010 Village received a letter from NYSDEC

citing unsound condition rating• May 2011 Engineering Assessment Report confirmed:

– Spillway, spillway chute and stilling basin did not have sufficient capacity

– Low level outlet (mud) pipe inadequate– Embankment stability didn’t meet all published safety factors– Crest elevation varied and did not provide adequate freeboard

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Design ImprovementsRequired:

• Modifications to the Spillway, Spillway Chute and Stilling Basin

• New Filtered Toe Drain

• New Intake Structure, Low Level Outlet and Supply Pipes

• Stump/Vegetation Removal along the Crest and Embankment

• Leveling of the Dam Crest and Corewall

• Wave Protection Improvements

Optional:

• New Floating Dock System to Access Sampling Locations

• Construction of a Safer Access Bridge

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Spillway and Access Bridge – Before• Multi-level broad crested weir

with two 4.6 ft wide openings

• Crest EL of 188.5

• Narrow footbridge for maintenance access

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Spillway and Access Bridge – After

• 2-cycle labyrinth weir

• Weir height EL 188.5

• Wider access bridge

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Spillway Outlet and Chute – Before• Masonry block lined,

trapezoidal channel

• 180 ft in length

• Channel depths of 4-6 ft

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Spillway Outlet and Chute – After

• Rectangular, smooth concrete channel

• Minimum height of 5 ft and width of 10 ft

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Stilling Basin – Before• Concrete overflow weir

• 28 ft wide, crest EL 162.8

• Concrete blocks on crest

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Stilling Basin – After

• Crest lowered to EL 159

• Sidewalls raised with fencing

• Low level outlet provided

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Embankment Toe – Before• Moisture at toe with

vegetation but

• No internal erosion, piping, soil heave or boil

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Embankment Toe – After

• 8” perforated pipe in drainage stone and filter sand

• (2) clean outs

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Embankment Toe – After• One of a number of

piezometers with new pedestal and access cover

• Routinely measuring ground water level

• Toe drain discharge chamber with weir for flow measurement

• Observe discharge quality

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Dam Crest and Wave Protection – Before• Undulating crest

• Minimal riprap and much vegetation on upstream side

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Dam Crest and Wave Protection – After

• Crest leveled to EL 193

• Corewall raised

• Riprap installed

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LLO & Supply Piping• Trenchless installation

• 60” casing pipe

• (2) 16” and (1) 18” pipe

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Successful Project!• Upgrade the almost 130-year old IBRD to meet current regulatory and

industry safety and operational standards

• Ensure sustainability for the Village’s water supply

• Deliver the best water quality available

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Assessment of Learning

• Can you identify various types of dams, their functions and their hazard classifications?

• How can dams fail?• Why did dam regulations come into

effect?• Can you describe some of the NYS

DEC Dam Safety Requirements?• Can you apply dam safety design

criteria to an existing Class C, High Hazard earthen dam?

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Thank you!Questions/Discussion

24 September 2018