NY Rising Reconstruction Program Project UpdateRye City Council Monthly Meeting

PRESENTERS:

Bradley Cantor

Governor’s Office of Storm Recovery

(GOSR)

Regional Lead

Brian Platt

O’Brien & Gere Engineers,

Inc. (OBG)

Engineer

Peter Johantgen

Dormitory Authority of the State of New York

(DASNY)

Project Manager

Kate Seely-Kirk

Dormitory Authority of the State of New York

(DASNY)

Director Construction Administration

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Bowman Dam Automation - Benefit-Cost-Analysis (BCA) Results Summary

Milton Road Drainage Improvements Results Summary

PRESENTATION OUTLINE

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Objective #2: Sluice Gate Operation – Assess effectiveness of previously proposed operating algorithm when combined with work performed in Objective #1

Objective #1: Expansion of Upper Pond – Refinement to match available funding ($2 million)

PREVIOUS STUDY - ANALYSIS OF UPPER POND RESIZING

Bowman Dam

2000 4000 6000 8000

10

20

30

40

50

BowmanDamProject Plan: 1) OBG_exist-10y 11/30/2016 2) OBG-Plan-13KCUT -10y 11/30/2016 3) OBG-Plan-13KCUT -10y-PB@I-287-new 12/1/2016

Main Channel Distance (ft)

Ele

vation

(ft)

Legend

WS Max WS - OBG_exist-10y

WS Max WS - OBG-Plan-13KCUT-10y

WS Max WS - OBG-Plan-13KCUT-10y-PB@I-287-new

Ground

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PREVIOUS STUDY – RESULTS COMPARISON – POND EXPANSION VS. SLUICE GATE OPERATION

I-95 I-287

Highland Rd.Purchase St.

10-YEAR FLOOD

EXCAVATION+

SLUICE GATE

13.5K EXCAV.

Existing WSE

Conclusion: The benefits associated with Upper Pond resizing are an order of magnitude less than the benefits from utilizing a gate operation strategy.

13.5k CY Excavation + Sluice Gate

Ap

pro

x. ~

0.7

ft.

Stream Bed

5

-0.50

0.00

0.50

1.00

1.50

2-Y

ear 1 2 3 4

5-Y

ear 1 2 3 4

10

-Yea

r 1 2 3 4

25

-Yea

r 1 2 3 4

50

-Yea

r 1 2 3 4

10

0-Y

ear 1 2 3 4

PB@Indian Village

PB@l-287

2-year 5-year 25-year10-year 50-year 100-year

PREVIOUS STUDY – RESULTS COMPARISON – PB ALGORITM BY CONTROL LOCATION

Conclusions: • The gate should

remain open for events < 5-yearreturn frequency

• Selection of algorithm control location may influence observed WSE reductions

• Majority of reduction is attributed to sluice gate control

Wat

er S

urf

ace

Elev

atio

n R

edu

ctio

n (

ft)

Locations (1 2 3 4)

SLUICE GATE AT BOWMAN DAM

6

Gate installed: 2013

EXISTING CONDITION

The dam in fixed “closed” position

Previously developed operational algorithms not implemented

Need for additional stream monitoring stations and system integration

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BENEFIT COST ANALYSIS STUDY OBJECTIVES

Compare the following:

Costs of stream gauge construction and sluice gate operation

Benefits associated with avoided property damage if stream gauges were constructed and integrated with existing sluice gate

Comparison is made by calculating a Benefit Cost Ratio

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BENEFIT COST RATIO

FEMA Benefit-Cost Analysis (BCA) Toolkit

The outcome is a Benefit-Cost Ratio (BCR)

BCR > 1A project is economically viable

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CONCEPTUAL DESIGN PROCESS – STREAM GAUGES

Site visit performed to identify potential gauge locations.

Radio survey performed to assess data transmission options

• Due to terrain and vegetation, cellular technology is proposed

Modeling performed to estimate potential water surface elevation reduction

Conceptual gauge and instrumentation design performed

Conceptual capital cost estimation

Operation and maintenance cost estimation

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COST ESTIMATION

Components: Stream gauge and gate control system design, construction, and operation

Stream monitoring system design

Means of gauge communication

Data storage and access

Existing infrastructure integration

Model & algorithm calibration

Implementation

Operation & maintenance

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PROPOSED GAUGE LOCATION BROOKSIDE WAY (UPSTREAM)

GAUGE

12

PROPOSED GAUGE LOCATION PURCHASE ST. (DOWNSTREAM)

GAUGE

13

BENEFIT ESTIMATION

Benefit Component: Potentially avoided property damage

If flood elevations are reduced by approximately 1 foot, how would residential flood damage be reduced?

• Estimate number of residences affected by reduction

• Estimate avoided damage costs

EXIS

TIN

G

PR

OP

OSE

D

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BENEFIT COST ANALYSIS SUMMARY

TOTAL ESTIMATED BENEFITS: $10,800,000 TOTAL ESTIMATED COST: $630,000

Benefit cost ratio (BCR) is 14

BCR is greater than 1, therefore the project is economically viable

AVOIDED PROPERTY DAMAGE: $8,800,000

SOCIAL BENEFITS: $2,000,000 ANNUAL MAINTENANCE: $25,000

INITIAL COST: $398,000

Notes:

1. Values are expressed in 2017 dollars

2. Annual maintenance portion of the total estimated cost is expressed in 2017 dollars assuming 7% annual discount rate. Annual maintenance would not be funded with NY Rising Project funding.

3. Project life assumed to be 15 years (i.e., instrumentation and controls are assumed to require updating after 15 years of use).

Notes:

1. Mental stress and anxiety includes treatment cost per person

2. Values are expressed in 2017 dollars

APPROXIMATE BENEFITS APPROXIMATE COSTS

Milton Road Drainage Improvements Study

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CATCH BASIN

MANHOLE

OUTLET

MILTON HARBOR HOUSE AREA

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DRAINAGE AREA

SYSTEM OUTFALL Flow generating rainfall

Tidal conditions in the bayAverage High Tide: 3.4 ft

(NAVD88)

MODEL INPUTS

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EXISTING CONDITIONS: CURRENT STORMWATER SYSTEM CONFIGURATION

MODELED CONDITIONS:TIDE: 3.4 ft

WITH CHECK VALVE AT SYSTEM OUTFALLRAINFALL EVENT: 10-YEAR STORM

MODEL VIEW: PLAN VIEW MODEL VIEW: PROFILE

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REPLACE WITH 24” PIPE

REPLACE WITH 24” PIPE

REPLACE WITH 24” PIPE

PROPOSED IMPROVEMENTS: REPLACE EXISTING PIPES

EXISTING CONDITIONSTIDE ELEVATION: 3.4 FT

WITH CHECK VALVE AT OUTFALLRAINFALL EVENT: 10-YEAR STORM

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REPLACE WITH 24” PIPE

REPLACE WITH 24” PIPE

REPLACE WITH 24” PIPE

PROPOSED CONDITIONSTIDE ELEVATION: 3.4 FT

WITH CHECK VALVE AT OUTFALLRAINFALL EVENT: 10-YEAR STORM

PROPOSED IMPROVEMENTS: REPLACE EXISTING PIPES

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MODELED CONDITIONS:TIDE: 3.4 ft

WITH CHECK VALVE AT SYSTEM OUTFALLRAINFALL EVENT: 10-YEAR STORM

PROFILE VIEW: EXISTING CONDITIONSPROFILE VIEW: PROPOSED IMPROVEMENTS

(INCREASE PIPE SIZES)

PROPOSED IMPROVEMENTS: REPLACE EXISTING PIPES

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NYS DEC SEA-LEVEL RISE PROJECTION REGULATION

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REPLACE WITH 24” PIPE

REPLACE WITH 24” PIPE

REPLACE WITH 24” PIPE

PROPOSED IMPROVEMENTS: REPLACE EXISTING PIPES

2050 CONDITIONSTIDE ELEVATION: 4.7 FT

WITH CHECK VALVE AT OUTFALLRAINFALL EVENT: 10-YEAR STORM

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REPLACED WITH 24” PIPE

REPLACED WITH 24” PIPE

REPLACED WITH 24” PIPE

PROPOSED IMPROVEMENTS: REPLACE EXISTING PIPES

PROPOSED CONDITIONSTIDE ELEVATION: 4.7 FT

WITH CHECK VALVE AT OUTFALLRAINFALL EVENT: 25-YEAR STORM

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CATCH BASIN

MANHOLEOUTLET

DIVERTING WATER BY CONNECTING DRAINAGE SYSTEMS

PROPOSED CONNECTION

EXISTING DRAINAGE

SYSTEM

OUTLET

MODEL CONDITIONSTIDE ELEVATION: 4.7 FT

WITH CHECK VALVE AT OUTFALLRAINFALL EVENT: 25-YEAR STORM

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MILTON HARBOR HOUSE AREA SUMMARY

Replacing existing pipes would reduce flooding on Milton Harbor House property during a 10-year

storm event

Flooding would be reduced for both the current high tide of 3.4 feet and projected 2050 high tide of

4.7 feet

In addition to replacing existing pipes, constructing a pipe to divert water to an adjacent storm sewer

system would provide additional capacity to manage larger storms

Hewlett Street Area

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HEWLETT STREET SYSTEM CONFIGURATION

RECOMMEND INSTALLING

CHECK VALVE

LOCATION OF PERIODIC

FLOODING

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HEWLETT STREET PROPOSED IMPROVEMENTS

Prevents water and sediment from entering the pipe

Creates additional storage for storm water

Slightly reduces flooding at Hewlett Street and

Milton Road intersection

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COST ANALYSIS SUMMARY

STORM SEWER IMPROVEMENT CONCEPTUAL CONSTRUCTION COST

Replace Existing Pipes (Milton Harbor House Area) $310,000

Replace Existing Pipes & Divert Water (Milton Harbor House Area) $647,000

Check Valve (Hewlett Street & Milton Road Intersection) $55,000

Note:Construction costs do not include engineering and construction oversight costs.

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NY Rising Reconstruction Program Project UpdateRye City Council Monthly Meeting

QUESTIONS?