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Master Plan

Nashua Fire Rescue, NH

The Nashua Hazard Mitigation Action Plan includes a very thorough community risk assessment. The

following section summarizes the process that led to the development of the plan as well as the resulting
Hazard Assessments, Goals, and Objectives. ESCI will then correlate the Hazard Mitigation Plan with the
Historical Service Demand and Performance of the City of Nashua.

Hazard and Risk Identification Process

The hazards in the Hazard Mitigation Plan Update 2019 align with the hazard names identified in the State
of New Hampshire Multi-Hazard Mitigation Plan Update 2018. Two hazards identified in the State plan that
do not impact Nashua are Avalanche and Coastal Flooding.

Avalanche

Coastal
Flooding

Inland
Flooding

Figure 35. Natural Hazards in Jurisdiction

Hazard Type Hazard Location Hazard Extent impact

This hazard does not occur in Nashua

This hazard does not occur in Nashua

All special flood hazard areas; areas
have been identified that experience
localized flooding on a regular basis.
Slopes along Merrimack & Nashua
Rivers prone to erosion.

Roadways with the potential to flood
include:

FEE Turnpike: Southbound at crossing
of Spit Brook Rd

Circumferential Hwy: Within Floodway
Daniel Webster Hwy: In 1% and .2%
Floodplain at Royal Crest Dr

Canal St: From Merrimack River to
Salvail Ct

Bridge St: Within Area With Reduced
Risk Due to Levee

E Dunstable Rd: Proximity to
Floodway and .2% Floodplain but no
flooding

Main Dunstable Rd: Within .2%
Floodplain from Valhalla Dr to Memory
Ave;

Proximity to .2% Floodplain for much
of its run

Spit Brook Rd: Within 1% Floodplain at
intersection with FEE Turnpike

W Hollis St: Within Floodway at
Nashua River crossing

E Hollis St: Within Area With Reduced
Risk Due to Levee from Denton Street
to Crown Street/Merrimack River
Concord St: Within Floodway/1%
Floodplain at crossing of Pennichuck
Brook and change into DW Highway
Broad St: Within .2% Floodplain at
Canter Ct and Broadcrest Ln, proximity
to .2% Floodplain at Spar Ave

Main St: Within Floodway at Nashua
River crossing

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This hazard does not occur in Nashua

This hazard does not occur in Nashua

FEMA flood probability elevation:
1%
0.2%

In the 1960s, the United States
government decided to use the 1%
annual exceedance probability (AEP)
flood as the basis for the National Flood
Insurance Program. The 1% AEP flood
was thought to be a fair balance
between protecting the public and
overly stringent regulations. Because
the 1% AEP flood has a1in 100 chance
of being equaled or exceeded in any 1
year, and it has an average recurrence
interval of 100 years, it often is referred
to as the “100-year flood.”

More recently, people talk about larger
floods, such as the "5o0o0-year flood," as
tolerance for risk is reduced and
increased protection from flooding is
desired. The "soo-year flood"
corresponds to an AEP of 0.2%, which
means a flood of that size or greater has
a 0.2% chance (or 1 in 500 chance) of
occurring in a given year.

This hazard does not occur in Nashua

This hazard does not occur in Nashua

Water damage to structures and their
contents.

Damage or loss of infrastructure,
including roads, bridges, railroads,
power and phone lines, City
communications, City radio system,
power generation facility, domestic
water, and wastewater treatment
plant.

Environmental hazards resulting from
damage.

Isolation of neighborhoods resulting
from flooding.

Sewer backups.

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Master Plan

Nashua Fire Rescue, NH

Hazard Type Hazard Location Hazard Extent impact

Drought

Allds St: Within Floodway at Salmon
Brook crossing

Pine Hill Rd: Within .2% Floodplain
near intersection with Perimeter Rd

Manchester St: Within Floodway at
Harris Pond and within .2% Floodplain
near Tinker Rd

Broad Street Pkwy: Within .2%
Floodplain on approach to Nashua
River crossing and crosses Floodway

Types of Roads Included:

Highways: The top of the hierarchy.
They are limited access, provide largely
uninterrupted travel over long
distances and are designed for high
speeds. Example: Everett Turnpike
Arterial Roads: The next level of
roadways. They serve to move large
volumes of traffic through a town or to
connect one section of town with
another section. Example: NH 101A
Collector Roads: Act to feed traffic to
or from local roads and arterials.
Collector roads provide direct access to
abutting properties and distribute it to
or from arterials. Traffic using a
collector is usually going to or coming
from somewhere nearby. Example:
Henri Burke Highway

Entire jurisdiction NH DES Drought Management Plan:
Level 1—Alert
Level 2—Warning
Level 3—Emergency
Level 4—Disaster

U.S. Drought Monitor
Do—Abnormally Dry
Da—Moderate Drought
D2—Severe Drought
D3-Extreme Drought
D4—Exceptional Drought
S—Short term, typically less than 6
months
L—Long term, typically more than 6
months

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Do
Short term dryness slowing
planting, growth of crops
Some lingering water deficits
Crops not fully recovered

Da
Some damage to crops

Streams, reservoirs, or wells low,
some water shortages developing
or imminent
Voluntary water-use restrictions
requested

D2
Crop losses likely
Water shortages common
Water restrictions imposed

b3
Major crop losses
Widespread water shortages or
restrictions

D4
Exceptional & widespread crop
loss

Shortages of water in reservoirs,
streams, & wells creating water
emergencies

Impacts on agriculture

Impacts on hydrology & ecology

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Master Plan

Nashua Fire Rescue, NH

Hazard Type Hazard Location Hazard Extent impact

Earthquake Entire jurisdiction

Extreme Entire jurisdiction

Temperatures

High Wind Entire jurisdiction

Events

Infectious Entire jurisdiction

Diseases

Landslide Limited steep hills that are prone to

landslide in jurisdiction

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Richter Scale:
< 3.4 (detected only by
seismometers)
> 8 (total damage, surface waves
seen, objects thrown in air)
For full definitions of Richter Scale, see
Section 3.5 Vulnerability by Hazard

Extreme heat—period of 3 consecutive
days which air temperature reaches 9oF
or higher on each day.

Extreme cold—period of 3 consecutive
days of minimum temperatures at or
below oF

Enhanced Fujita Tornado Damage

Scale:
EFo—winds 65-85 mph
EFa—winds 86-110 mph
EF2—winds 111-135 mph
EF3—winds 136-165 mph
EF4—winds 166-200 mph
EFs5—winds over 200 mph

Disease epidemics

Large-scale incidents of food or water
contamination

Extended periods without adequate
sanitation services

While no universally accepted standard
or scientific scale has been developed
for measuring the severity of all
landslides, severity can be measured
several other ways:

Steepness/grade of the Slope

(measured as a percent)

Geographical Area

= Measured in square feet, square
yards, etc.

= More accurately measured using
LIDAR/GIS systems

Overall:
Loss of crops
Inadequate quantity of drinking
water
Loss of water for fire protection
Increased risk of fire

Structural damage or collapse of
buildings

Damage or loss of infrastructure,
including roads, bridges, railroads,
power and phone lines, City
communications, City radio system,
power generation facility, domestic
water, and wastewater treatment
plant

Loss of water for fire protection
Increased risk of fire from gas break
Risk to life, medical surge
Overburdened power systems may

experience failures due to extreme
heat

Shortages of heating fuel in extreme
cold due to high demand.

Medical surge

Loss of municipal water supply for
drinking water and fire protection due
to freezing temperatures

Wind damage to structures and trees

Damage or loss of infrastructure,
including roads, bridges, railroads,
power and phone lines, City
communications, City radio system,
power generation facility, domestic
water, and wastewater treatment
plant

Environmental hazards resulting from
damage

Medical surge

Loss of natural resources

Burden on healthcare facilities

Possible quarantine to prevent disease
from spreading.

Structural damage or collapse of
buildings

Damage or loss of infrastructure,
including roads, bridges, railroads,
power and phone lines, City
communications, City radio system,
power generation facility, domestic
water, and wastewater treatment
plant

Loss of water for fire protection
Increased risk of fire from gas break

Risk to life, medical surge

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Master Plan

Nashua Fire Rescue, NH

Hazard Type Hazard Location Hazard Extent impact

Lightning

Severe
Winter
Weather

Solar Storms
and Space
Weather

Entire jurisdiction

Areas with large populations present
outdoors and large open spaces are
particularly vulnerable

Entire jurisdiction

Entire jurisdiction

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Earthquake, either causing the event
or caused by the event (measured
using the Moment Magnitude
Intensity or Mercalli Scale)
There are also multiple types of
landslides:
Falls: A mass detaches from a steep
slope or cliff and descends by free-
fall, bounding, or rolling
Topples: A mass tilts or rotates
forward as a unit
Slides: A mass displaces on one or
more recognizable surfaces, which
may be curved or planar
Flows: A mass moves downslope
with a fluid motion. A significant
amount of water may or may not be
part of the mass
Like flooding, landslides are unique in
how they affect different geographic,
topographic, and geologic areas.
Therefore, consideration of a multitude
of measurements is required to
determine the severity of the landslide
event.

Lightning Activity Level:
Level 1
Level 2
Level 3
Level 4
Level 5
Level 6
For full definitions of Lightning Activity

Level, see Section 3.5 Vulnerability by
Hazard

Depth of snow ina given time frame
(ex. 2 or more inches per hour over a 12-
hour period)

Blizzard—violent snowstorm with
minimum winds of 35 mph and visibility
less than % mile for 3 hours
Ground snow load factor
Ice Storm—Sperry-Piltz Ice
Accumulation Index:
o—little impact
5—catastrophic damage to exposed
utility systems
For full definitions of Sperry-Piltz Ice
Accumulation Index, see Section 3.5
Vulnerability by Hazard

Geomagnetic Storms:
Gs—Extreme
G4—Severe
G3—Strong
G2—Moderate
G1a—Minor

Solar Radiation Storms:

Smoke and fire damage to structures

Disruption to power lines, traffic
control systems, and communications

Damage to critical electronic
equipment

Injury or death to people involved in
outdoor activity

Disruption to road network

Damage to trees and power lines,
communications, gas lines
Structural damage to roofs/collapse.

Increase in CO, other hazards

Space weather can produce
electromagnetic fields that induce
currents in wires, disrupting power
lines and causing widespread power
outages

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Master Plan

Nashua Fire Rescue, NH

Hazard Type Hazard Location Hazard Extent impact

Tropical and
Post-Tropical
Cyclones

Wildfire

Entire jurisdiction

Forested areas in jurisdiction,
particularly in northwest and southwest
quadrants as well as in Mine Falls Park

Areas outside of municipal water
supply system

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S5—Extreme
S4—Severe
$3—Strong
S2—Moderate
S1—Minor
Radio Blackout:
Rs5—Extreme
R4—Severe
R3—Strong
R2—Moderate
Ra—Minor
For full definitions of NOAA Space

Weather Scales, see Section 3.5
Vulnerability by Hazard

Saffir-Simpson Hurricane Wind Scale:
Category 1—sustained winds 74-95
mph
Category 2—sustained winds 96-110
mph
Category 3—sustained winds 111—
129 mph
Category 4—sustained winds 130-
156 mph
Category 5—sustained winds 157
mph or higher

NWGG Fire Size Classification:
A—greater than o but less than or
equal to 0.25 acres
B—o.26 to 9.9 acres
C—41o.0 to 99.9 acres
D—100-299 acres
E—300 to 999 acres
F—1,000 to 4,999 acres
G—5,000 to 9,999 acres
H—10,000 to 49,999 acres
I—§0,000 to 99,999 acres
J—100,000 to 499,999 acres
K—500,000 to 999,999 acres
L—1,000,000+ acres

Severe space weather can produce
solar energetic particles, which can
damage satellites used for
communications, global positioning,
intelligence gathering, and weather
forecasting

Wind damage to structures and trees

Water damage to structures and their
contents

Damage or loss of infrastructure,
including roads, bridges, railroads,
power and phone lines, City
communications, City radio system,
power generation facility, domestic
water, and wastewater treatment
plant

Environmental hazards resulting from
damage

Isolation of neighborhoods resulting
from flooding

Water pressure, quality, and capacity
issues impacting fire protection

Loss of natural resources

Smoke and fire damage to structures
in wildland/urban interface

Damage on habitat

Impacts on air quality

Impact to roadways

Loss of natural resources

Potential for urban conflagration

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Master Plan Nashua Fire Rescue, NH

Prioritizing Risk
Nashua used the following process to identify risks within the community.

1. Identification of Hazards: For each hazard type, the hazard location within the city, extent, and
impact are noted within the Hazard Mitigation Plan.

2. Description of Previous Hazards: The first step in determining the probability of future hazard
events in the City of Nashua was to examine the location, extent, and impact of previous hazards.

3. Probability of Future Hazard Events: After documenting the occurrence of previous hazard events
in the City of Nashua and the surrounding region, the Resilient Nashua Initiative stakeholders used
this information to calculate the annual probability of these events occurring in the future.

a. The first step was to determine how many times a particular hazard had occurred in a given
number of years. The year range is based upon the most detailed database being used for
the assessment. Because of this, there may be anumber of significant hazard event outliers,
primarily before 1960, that are not included in the probability calculation due to limited
historical data. The number of occurrences was then divided by the number of years to
determine the average number of events per year. For example, if history shows that a
particular hazard typically occurs 1 time every 4 years, the average number of events per year
is 0.25. The average number of events per year was calculated twice for each hazard. First,
the average number of events per year was calculated since the first recorded historical
occurrence of the event.

b. Second, the average number of events per year was calculated based on occurrences since
2000 (up to 2016) to reflect potential recent changes in hazard event occurrence rates.

c. Finally, the estimated probability of one or more hazard events in any year was calculated

using the Poisson Distribution.** For the Poisson Distribution, ) is the average number of

events per year and X is 1 (the number of years to be evaluated for probability). The
calculation looked at the greater to or equal likelihood of occurrence.

4. Critical Faculties and Their Vulnerabilities: The next step in determining the City’s overall
vulnerability was to inventory Nashua’s community assets and determine what assets would be
affected by each type of hazard event. The Resilient Nashua Initiative stakeholders began by
reviewing the City of Nashua Land Use Code to provide information on where and how the City builds
and to identify the corridors where critical facilities would likely be located. The stakeholders then
identified the broad categories of important assets within the City, including critical facilities
essential to health and welfare; vulnerable populations, such as children and the elderly; economic
assets and major employers; areas of high-density residential and commercial development; and
historical, cultural, and natural resources.

5. Vulnerability by Hazard: Finally, Nashua’s vulnerability to each hazard was identified and
categorized.

21 https://homepage.divms.uiowa. edu/~mbognar/applets/pois. html.

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Master Plan

Nashua Fire Rescue, NH

Hazard Mitigation Goals, Priorities, and Strategies

The Resilient Nashua Initiative stakeholders developed a plan that specifies who is responsible for
implementing the prioritized mitigation actions, how they will be funded, and when they will be completed.

After completing a Benefit-Cost Review for each action in the plan, the Resilient Nashua Initiative
stakeholders then prioritized the actions by conducting a STAPLEE Analysis, which stands for Social,
Technical, Administrative, Political, Legal, Economic, and Environmental factors. For each mitigation action,

the stakeholders asked the following questions:

Figure 36. STAPLEE Analysis

STAPLEE Analysis

Social

Technical

Administrative

Political

Legal

Economic

Environmental

Will the action unfairly impact any one segment of the population?
Will it disrupt established neighborhoods? Is it compatible with present
and future community values? Will it adversely affect cultural
resources?

How effective is the action in avoiding or reducing future losses? Will
it create more problems than it solves? What are some secondary
impacts? Does it solve a problem or only a symptom?

Does the community have the capability to implement the action?
Can the community provide the necessary maintenance? Can it be
accomplished in a timely manner¢

ls there public support both to implement and maintain the action? Is
the political leadership willing to support it? Does it present a financial
burden to stakeholders?

Does the community have the authority to implement the action? Is
enabling legislation necessary? What are the legal side effects? Will
the community be liable for the actions, support of actions, or lack of
actions?

Economic What are the costs of this action? How will the costs be
bome? Are state/federal grant programs applicable? Does the
action fit into existing capital inprovements or economic
development budgets?

How will this action affect the environment? Does it comply with
local, state, and federal environmental regulations? Is it consistent
with community environmental goals? Are endangered or
threatened species likely to be affected?

The cost and benefit of each mitigation action were then evaluated and assigned a quantitative score based

onthe STAPLEE criteria.

Benefit Score Range: o = Not Beneficial, 1 = Somewhat Beneficial, 2 = Beneficial, 3 = Very Beneficial

Cost Score Range: 0 = Not Costly, -1 = Somewhat Costly, -2 = Costly, -3 = Very Costly

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Master Plan Nashua Fire Rescue, NH

Next, the scores for each action were added to determine priority. Finally, the Resilient Nashua Initiative
stakeholders reviewed the scores and resulting prioritization to make sure it was consistent with the City’s
goals and Master Plan. The STAPLEE prioritized mitigation actions appear in the following figure. STAPLEE
scores of o or below were determined to have costs that outweigh the benefits and will be reassessed in the
next plan update. These actions were not continued to the implementation review.

Figure 37. Nashua Hazard Mitigation Actions

Nashua Hazard Mitigation Actions

1. Signal failure prevention through additional wireless communications and backup power
sources.

2. Mast arm inspections throughout City.

3. Improve drainage capacity of problem flood areas, particularly Wethersfield/Westwood,

Shelly Drive and Browning Ave, Victor Ave at Emmett St, Westchester Dr, Wilmington Rd at New
Searles Rd, Pemberton Rd at Belfast St, Park Ave/Lawndale Ave area, Courtland St/Hall Ave
area; C, D, E Streets, Marshall St (Bowers to East Hollis}, and Spaulding Ave.

4. Work with Pennichuck to increase public awareness of methods to reduce water
consumption during drought conditions.

5. Improve outreach and education regarding mold and other health concerns resulting
from flooding.

é. Increase the capacity of culverts and storm drains and ensure drainage systems are
properly engineered, citizens are included in the planning process, particularly as part of future
paving initiatives.

7. Continue to work with Eversource to harden electrical infrastructure, including trimming
trees near power lines.

8. Enforce building codes, particularly those related to wind and snow load.

9. Provide ongoing outreach and education regarding snow load.

10. Work with local utilities to conduct public outreach and education to ensure energy users

are operating systems efficiently during times of extreme temperatures and are aware of
heating and cooling assistance options.

11. Enforce fire permit regulations.

12. Make available NFIP, insurance, and building codes explanatory pamphlets or booklets.

13. Enhance local officials, builders, developers, local citizens, and other stakeholders’
knowledge of how to read and interpret the Flood Insurance Rate Map (FIRM).

14, Routinely clean and repair stormwater drains.

15. Ask residents to help keep storm drains clear of debris during storms (not to rely solely on
Public Works).

16. Collect rainwater and use natural runoff to water plants.

17. Provide grassy swales along roadsides.

18. Add building insulation to walls and attics and conduct overall weatherization upgrades.

19. Install generators, solar + storage, and quick-connect emergency generator hook-ups for

critical facilities and other residential, commercial, industrial, & specialty properties.

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Master Plan Nashua Fire Rescue, NH

Nashua Hazard Mitigation Actions

20. Adopt the most current International Building Code (IBC) and International Residential
Code (IRC).

21. Promote the installation of air conditioners and heat pumps and opportunities to subsidize
the equipment and energy costs for low-income families.

22. Promote the installation of low-flow water saving showerheads and toilets and
opportunities to subsidize the equipment for low-income families.

23. Increase tree plantings around buildings to shade parking lots and along public rights-of-
way.

24. Encourage the installation of green roofs, which provide shade and remove heat from the
roof surface and surrounding air.

25. Work with insurance industry representatives to increase public awareness of the
importance of multi-hazard insurance and coverage limitations.

26. Install, repair and/or replace HVAC systems at public facilities, particularly at schools, the
library, fire stations, police department.

27. Install redundancies in municipal fiber and fire alarm network.

28. Incorporate hazard mitigation principles into all aspects of public-funded building.

29. Incorporate mitigation retrofits for public facilities into the annual capital improvements
program.

30. Incorporate a stand-alone element for hazard mitigation & resilience into the upcoming

master plan.

31. Add at least a 1-foot "freeboard" requirement (feet above base flood elevation) in the
flood damage ordinance to maintain Nashua's Class 8 CRS Rating in 2020.

32. Prepare and adopting a community-wide stormwater management master plan to
maintain compliance with the City's MS4 permit.

33. Implement an inspection, maintenance, and enforcement program to help ensure
continued structural integrity of municipal dams and the Merrimack River Right Bank — Flood
Damage Reduction System levee. Recommendations from the Army Corps of Engineers
inspection reports should be resolved to bring the levee to an “Acceptable” status.

34. Promote the Resilient Nashua Toolkit interactive website for educating the public on
hazard mitigation and preparedness measures.

35. Designated local floodplain manager and CRS coordinator achieve CFM certification.

36. Install, Uograde, or maintain back-up generators for pUMping and lift stations in sanitary
sewer systems along with other measures (e.g., alarms, meters, remote controls, and switchgear
Upgrades).

37. Raise utilities or other mechanical devices above expected flood levels, particularly in

areas likely to be redeveloped soon in the Millyard.

38. Wet floodproof basements residential and non-residential structures, which may be
preferable to attempting to keep water out completely because it allows for controlled flooding
to balance exterior and interior wall forces and discourages structural collapse, particularly in
areas likely to be redeveloped soon in the Millyard.

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Master Plan Nashua Fire Rescue, NH

Nashua Hazard Mitigation Actions

39. Identify the best approach to prevent new development or to require flood-resilient site &
building design in developable parcels adjacent to the Merrimack River.

40. Develop a coordinated GIS Department. Find out who uses GIS, determine how it is used,
and identify other potential uses.

41. Obtain hazard data and using GIS to map risk for various hazards.

42. Develop and maintain a database to track community exposure to flood risk, particularly

smaller nuisance events, for future benefit-cost analysis use.

The City of Nashua is now working to integrate requirements of the Nashua Hazard Mitigation Plan into other
planning mechanisms. Additionally, the City’s Capital Improvement Plan includes many of the large-scale
City mitigation projects that were identified in the Hazard Mitigation Plan, and the Division of Public Health
and Community Services is working on incorporating public health mitigation strategies into its Community
Health Improvement Plan update cycle. The Resilient Nashua Initiative will be responsible for helping other
City departments to integrate the Hazard Mitigation Plan into its own planning mechanisms.

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