Section 5.4.4 - Expansive Soils

Section 5.4.4: Risk Assessment – Expansive Soils

Hazard Mitigation Plan – Erie County, New York 5.4.4-1 Month 2021

5.4.4 Expansive Soils This section provides a hazard profile and vulnerability assessment of the expansive soils hazard.

5.4.4.1 Hazard Profile

This section presents the expansive soils hazard description, extent, location, previous occurrences and losses, and probability of future occurrences.

Hazard Description

Soils and soft rock that tend to swell or shrink due to changes in moisture content are known as expansive soils. Expansive soils are often referred to as swelling clays because clay materials are most susceptible to swelling and shrinking. Changes in soil volume present a hazard primarily to structures built on expansive soils. The most extensive damage occurs to highways and streets (FEMA 1997).

In the U.S., two major groups of rocks serve as parent materials of expansive soils and these are most common in the western portion of the country. The first group consists of ash, glass, and rocks of volcanic origin. The aluminum silicate minerals in these volcanic materials often decompose to form expansive clay minerals, known as montmorillonite. The second group consists of sedimentary rocks containing clay minerals, for example, the shales of the semiarid west-central states (FEMA 1997).

The current New York State Hazard Mitigation Plan (HMP) does not profile expansive soils. However, according to the 2014 NYS HMP update, expansive soils are any soil that expands when wet and shrinks when dry. Soils are tested using an accepted standard of measurement to determine swell potential. Expansive soils can exert pressures up to 14,000 pounds per foot, causing the breakdown of building foundations and structural integrity. Roadbeds may also be affected and could lead to avalanche and collapse when cutting into mountains and hillsides (NYS DHSES 2014).

Expansive soils contain minerals, such as smectite clays, that are capable of absorbing water. As these clays absorb water, they increase in volume. The more water absorbed, the more their volume increases. Expansions of 10% or more are not uncommon. This change in volume can exert enough force on a building or other structure to cause damage. When dry, expansive soils shrink and can remove support from buildings or other structures and result in damaging subsidence. Fissures in the soil can also develop. Fissures can facilitate the deep penetration of water when moist conditions or runoff occurs. This produces a cycle of shrinkage and swelling that places repetitive stress on structures (NYS DHSES 2014).

Issues associated with expansive soils include:

• Foundation cracks • Heaving and cracking on floor slabs and walls • Jammed doors and windows • Ruptured pipelines • Heaving and cracking of sidewalks and roads • Damage to the upper floors of the building (when motion in the structure is significant) (NYS DHSES

2014)



Extent

The extent to which soil expansion is present in an area or site can be measured using the Soil Expansion Potential standard (ASTM D-4829). The expansion index (EI) provides an indication of swelling potential of a compacted soil. The EI test is not used to duplicate any particular field conditions such as soil density, water content, loading, in-place soil structure, or soil water chemistry.

Table 5.4.4-1. Soil Expansion Index

Expansion Index Potential Expansion 0-20 Very Low

21-50 Low 51-90 Medium 91-130 High >130 Very High

Source: ASTM 2013 Note: The Uniform Building Code (UBC) mandates that special foundation

design consideration be employed if the EI is 20 or greater. Based on the expansion potential rating, mitigation may be required for building construction or repairs. The UBC mandates that special foundation design consideration be employed if the EI is 20 or greater. The New York Residential Building Code (Section R403.1.8) addresses consideration of expansive soils. Construction dangers are reduced when engineers incorporate cement or lime or other salts into expansive soils. These help to lessen the effects of expansion. Other methods of reducing expansive soil danger include replacing the top three to four feet of expansive soil with non-expansive soils or compacting existing expansive soil.

Linear extensibility is also used to determine the shrink-swell potential of soils. The shrink-swell potential is low if the soil has a linear extensibility of less than 3 percent; moderate if 3 to 6 percent; high if 6 to 9 percent; and very high if more than 9 percent (refer to Table 5.4.4-2.). If linear extensibility is more than 3, shrinking and swelling can cause damage to buildings, roads, and other structures and plant roots. As noted, special design is commonly needed; however, this data does not replace a geotechnical exploration and report used to determine expansive soil potential (USDA Natural Resource Conservation Services, 2020).

Table 5.4.4-2. Linear Extensibility Ratings

Percent Linear Extensibility Shrink-Swell Potential 0-3 Low 3-6 Moderate 6-9 High

9-13 Very High Source: USDA NRCA 2020

Location

A custom soil report was run for Erie County using USDA Natural Resources Conservation Area soils data. Out of the 211 types of soils in Erie County, 31 are considered to have moderate linear extensibility potential. These soils primarily occur in the northern half of the county and cover approximately 96,917 acres or 14.2 percent of the entire county. The highest-rated soils are Odessa Lakemont complex and Odessa silt loam soils, which have a median percent linear extensibility of 5.7 percent. This is considered to be moderate shrink-swell potential. Figure 5.4.4-1 illustrates the location of the linear extensibility potential in Erie County.



Figure 5.4.4-1. Expansive Soils in Erie County



Previous Occurrences and Losses

There have been no federally declared disasters for expansive soils in New York State. According to the New York State Geological Survey (NYSGS), historical records, including scientific study data for land subsidence in the state, is either sparse, not readily available, or does not exist in summary form. There may have been incidents of expansive soils causing damage, but these incidents have not been reported (NYS DHSES 2013).

Historic occurrences of damage caused by expansive soils are only known to be located in the Town of Amherst, generally in the area north of Main Street. In the 2015 Erie County HMP, the United States Armey Corps of Engineers (USACE) reported that between the years 1987 and 2005 – 3 to 4 percent of the total residential structures in the town reported slight to severe foundation-related damage and/or structural damage, in part due to building on expansive soils. New development generally has few reported problems. At that time, the USACE also determined that average total repair costs for damaged homes is about $7,900 but ranges from about $500 to $71,000.

Probability of Future Occurrences

In Section 5.3, the identified hazards of concern for Erie County were ranked. The probability of occurrence, or likelihood of the event, is one parameter used for hazard rankings. Based on historical records and input from the Planning Committee, the probability of occurrence for expansive soils in Erie County is considered “occasional”.

Although no reported incidents have occurred within the county, it is anticipated that Erie County may experience indirect impacts from expansive soils that may affect the general building stock and the local economy and may induce secondary hazards, such as fires and utility failure.

Climate Change Impacts

Climate change is beginning to affect both people and resources of Erie County, and the impacts of climate change will continue. Impacts related to increasing temperatures are already being felt in the county. ClimAID: the Integrated Assessment for Effective Climate Change in New York State (ClimAID) was undertaken to provide decision-makers with information on the state’s vulnerability to climate change and to facilitate the development of adaptation strategies informed by both local experience and scientific knowledge. Each region in New York State, as defined by ClimAID, contains attributes that will be affected by climate change. Erie County is part of Region 1, Western New York, Great Lakes Plain. In Region 1, it is estimated that temperatures will increase by 3.0 ºF to 5.5 ºF by the 2050s and 4.5 ºF to 8.5 ºF by the 2080s (baseline of 48.0 ºF, mid-range projection). Precipitation totals will increase between 0 and 10% by the 2050s and 0 to 15% by the 2080s (baseline of 37.0 inches, mid-range projection). w displays the projected seasonal precipitation change for ClimAID Region 1 (NYSERDA 2014).

Table 5.4.4-3. Projected Seasonal Precipitation Change in Region 1, 2050s (% change)

Winter Spring Summer Fall +5 to +15 0 to +10 -5 to +10 -5 to +10

Source: NYSERDA 2014

By the end of the century, the greatest increases in precipitation are projected to be in the northern parts of the state. Although seasonal projections are less certain than annual results, much of this additional precipitation is projected to occur during the winter months. During the late summer and early fall, in contrast, total precipitation is slightly reduced in many climate models. The projected increase in precipitation is expected to fall in heavy downpours and less in light rains. The increase in heavy downpours has the potential to affect drinking water;



heighten the risk of riverine flooding; flood key rail lines, roadways, and transportation hubs; and increase delays and hazards related to extreme weather events (NYSERDA 2018).

Average annual temperatures are projected to increase across New York State by 2.0–3.4 ˚F by the 2020s, 4.1–6.8 ˚F by the 2050s, and 5.3–10.1 ˚F by the 2080s. By the end of the century, the greatest warming is projected to be in the northern parts of the state. The state’s growing season could lengthen by about a month, with summers becoming more intense and winters milder (NYSERDA 2018).

Increasing air temperatures intensify the water cycle by increasing evaporation and precipitation. This can cause an increase in rain totals during events with longer dry periods in between those events. These changes can have a variety of effects on the state’s water resources (NYSERDA 2011). Figure 5.4.4-2 displays the project rainfall and frequency of extreme storms in New York State. The amount of rainfall in a 100-year event is projected to increase, while the number of years between such storms (return period) is projected to decrease. Rainstorms will become more severe and more frequent (NYSERDA 2011).

Figure 5.4.4-2. Projected Rainfall and Frequency of Extreme Storms

Source: NYSERDA 2011

Total precipitation amounts have slightly increased in the Northeast U.S. by approximately 3.3 inches over the last 100 years. There has also been an increase in the number of two-inch rainfall events over a 48-hour period since the 1950s (a 67 percent increase). The number and intensity of extreme precipitation events are increasing in New York State as well. More rain heightens the danger of localized flash flooding, streambank erosion, and storm damage (Cornell University College of Agriculture and Life Sciences 2011).

Increased heavy precipitation events are expected in New York State due to climate change. As previously stated, as expansive soils absorb more water, they increase in volume, creating the potential to exert enough force on a building or other structure to cause damage. Temperatures are expected to increase throughout New York State. Increasing temperatures can increase the rate at which soils dry. When expansive soils are dry, they shrink and can remove support from buildings or other structures, resulting in damaging subsidence.



5.4.4.2 Vulnerability Assessment

To understand risk, a community must evaluate what assets are exposed and vulnerable in the identified hazard area. An exposure analysis was conducted in GIS for the expansive soils hazard area utilizing Canadice silt loam soils. Refer to Section 5.1 (Methodology and Tools) for additional details on the methodology used to assess expansive soil hazard area risk.

As indicated by earlier sections, there are 31 soils considered to have moderate shrink-swell potential. The soils with the greatest median linear extensibility are Odessa silt loam and Odessa Lakemont complex (0 to 3 percent slopes). There are no soils with a median extensibility greater than moderate in the county.

Impact on Life, Health and Safety

According to the 2019 ACS annual estimate, Erie County had a population of 919,355 people. The Town of Amherst has the greatest population at risk of events caused by expansive soils (24,209 people). The Town of Grand Island has the greatest percentage of population exposed to expansive soils (78.2 percent of the total population). Table 5.4.4-4 shows that an estimated 7 residents and 92 residents live on the expansive soils hazard area in the Town of Southampton and Town of Southold, respectively.

Table 5.4.4-4. Population Exposed to Expansive Soil Hazard Areas

Jurisdiction American Community Survey

(2014-2018) Population

Estimated Population Exposed to Expansive Soils

Moderate Expansive Soils Number of People Percent of Total

Akron (V) 2,871 0 0.0% Alden (T) 7,418 660 8.9% Alden (V) 2,577 966 37.5% Amherst (T) 120,276 24,209 20.1% Angola (V) 2,373 70 3.0% Aurora (T) 7,599 743 9.8% Blasdell (V) 2,645 0 0.0% Boston (T) 8,042 650 8.1% Brant (T) 1,541 105 6.8% Buffalo (C) 256,480 2,384 0.9% Cheektowaga (T) 73,129 4,217 5.8% Clarence (T) 32,440 8,442 26.0% Colden (T) 3,328 281 8.4% Collins (T) 5,418 332 6.1% Concord (T) 4,186 408 9.7% Depew (V) 15,102 916 6.1% East Aurora (V) 6,184 772 12.5% Eden (T) 7,631 1,165 15.3% Elma (T) 11,732 2,147 18.3% Evans (T) 13,782 2,535 18.4% Farnham (V) 459 11 2.4% Gowanda (V) 1,043 0 0.0% Grand Island (T) 21,047 16,456 78.2% Hamburg (T) 45,985 17,156 37.3% Hamburg (V) 9,636 71 0.7% Holland (T) 3,355 319 9.5% Kenmore (V) 15,132 0 0.0% Lackawanna (C) 17,831 576 3.2% Lancaster (T) 27,625 12,789 46.3% Lancaster (V) 10,144 2,837 28.0% Marilla (T) 5,378 290 5.4% Newstead (T) 5,804 60 1.0%



Jurisdiction American Community Survey

(2014-2018) Population

Estimated Population Exposed to Expansive Soils

Moderate Expansive Soils Number of People Percent of Total

North Collins (T) 2,130 129 6.1% North Collins (V) 1,370 186 13.6% Orchard Park (T) 26,361 5,507 20.9% Orchard Park (V) 3,148 29 0.9% Sardinia (T) 2,780 53 1.9% Sloan (V) 3,562 73 2.1% Springville (V) 4,298 51 1.2% Tonawanda (C) 14,830 199 1.3% Tonawanda (T) 57,027 1,163 2.0% Wales (T) 3,020 56 1.8% West Seneca (T) 45,344 10,670 23.5% Williamsville (V) 5,233 309 5.9% Erie County Total 917,296 119,992 13.1%

Source: American Community Survey 2019; USDA/NRCS 2020 Notes: T = Town, V = Village, C = City, % = percent * Cattaraugus Tribal Territory and Tonawanda Tribal Territory were not included in the above totals, as the two tribes did not participate in this HMP update.

Impact on General Building Stock

Because of differences in building construction, residential structures and one-story commercial structures are more susceptible to damage by expansive soils compared to multi-story buildings. Multi-story buildings are heavier and can generally counter the swelling pressures. The exception is when multi-story buildings are built on wet clay and may experience damage by shrinkage of the clay if moisture levels are substantially reduced (by evapotranspiration or by evaporation from under heated buildings) (FEMA 1997).

FEMA’s Coastal Construction Manual recommends that any development along the coast should follow the 2012 IBC requirements (FEMA n.d.). The 2012 IBC requires that geotechnical investigations are conducted if expansive soils are likely to be present. Subsurface testing includes boring, creating test pits, soil sampling, and laboratory tests. If an expansive soil is present, it is recommended that development does not occur. Table 5.4.4-5. summarizes the estimated number of buildings currently built on expansive soil hazard areas. The Town of Amherst has the greatest number of buildings and associated replacement cost value within the expansive soil hazard area (7,726 buildings and $5.8 billion). The Town of Grand Island has the greatest percentage of its buildings exposed to expansive soils (77.8 percent).

Table 5.4.4-5. Estimated Building Exposure to the Expansive Soils Hazard Areas

Wildfire Hazard Area Number of Buildings

Total Replacement Cost Value

(RCV)

Estimated Building Stock Exposed to Moderate Expansive Soils

Number of Buildings

Percent of Total

Replacement Cost Value

(RCV)

Percent of Total

Akron (V) 1,275 $866,609,574 0 0.0% $0 0.0% Alden (T) 3,400 $1,748,473,245 298 8.8% $128,622,043 7.4% Alden (V) 1,102 $602,655,574 396 35.9% $185,379,522 30.8% Amherst (T) 38,528 $27,372,255,690 7,726 20.1% $5,813,313,261 21.2% Angola (V) 874 $525,704,230 24 2.7% $9,014,159 1.7% Aurora (T) 4,280 $2,496,885,036 417 9.7% $265,538,480 10.6% Blasdell (V) 1,026 $638,571,953 6 0.6% $24,596,890 3.9% Boston (T) 4,040 $1,702,475,276 321 7.9% $125,218,929 7.4% Brant (T) 1,325 $657,594,060 81 6.1% $21,483,054 3.3% Buffalo (C) 83,471 $58,603,851,634 756 0.9% $337,807,970 0.6%



Wildfire Hazard Area Number of Buildings

Total Replacement Cost Value

(RCV)

Estimated Building Stock Exposed to Moderate Expansive Soils

Number of Buildings

Percent of Total

Replacement Cost Value

(RCV)

Percent of Total

Cheektowaga (T) 30,938 $17,530,893,277 1,876 6.1% $1,626,137,655 9.3% Clarence (T) 13,660 $9,866,246,863 3,452 25.3% $2,524,048,964 25.6% Colden (T) 2,110 $854,417,381 182 8.6% $77,558,949 9.1% Collins (T) 2,521 $1,189,158,504 175 6.9% $74,129,751 6.2% Concord (T) 3,245 $1,338,570,261 292 9.0% $102,561,460 7.7% Depew (V) 6,532 $3,841,823,815 453 6.9% $682,322,037 17.8% East Aurora (V) 2,441 $1,723,816,550 290 11.9% $211,464,460 12.3% Eden (T) 4,290 $2,180,455,513 656 15.3% $470,796,887 21.6% Elma (T) 6,093 $3,775,039,302 1,104 18.1% $557,499,664 14.8% Evans (T) 7,952 $3,335,060,692 1,423 17.9% $492,675,750 14.8% Farnham (V) 189 $87,990,422 4 2.1% $1,548,017 1.8% Gowanda (V) 396 $249,516,940 0 0.0% $0 0.0% Grand Island (T) 8,426 $4,674,517,058 6,552 77.8% $3,563,177,171 76.2% Hamburg (T) 19,130 $11,911,210,828 7,030 36.7% $3,531,403,260 29.6% Hamburg (V) 3,794 $2,005,172,252 26 0.7% $7,279,494 0.4% Holland (T) 2,182 $1,151,194,342 250 11.5% $119,412,106 10.4% Kenmore (V) 6,017 $2,305,529,001 0 0.0% $0 0.0% Lackawanna (C) 6,751 $4,030,622,400 208 3.1% $67,179,569 1.7% Lancaster (T) 10,973 $6,845,493,469 5,006 45.6% $2,738,580,914 40.0% Lancaster (V) 4,323 $2,217,331,122 1,245 28.8% $868,235,822 39.2% Marilla (T) 2,956 $1,099,846,031 163 5.5% $60,177,050 5.5% Newstead (T) 4,202 $2,181,758,974 34 0.8% $14,132,607 0.6% North Collins (T) 1,898 $889,517,676 91 4.8% $32,629,027 3.7% North Collins (V) 551 $383,968,909 72 13.1% $33,965,891 8.8% Orchard Park (T) 10,748 $8,174,650,530 2,311 21.5% $1,728,383,735 21.1% Orchard Park (V) 1,211 $867,347,745 10 0.8% $4,680,599 0.5% Sardinia (T) 2,184 $1,068,523,829 49 2.2% $21,987,877 2.1% Sloan (V) 1,674 $634,998,253 32 1.9% $9,403,845 1.5% Springville (V) 1,816 $1,354,905,864 22 1.2% $24,631,650 1.8% Tonawanda (C) 6,452 $3,291,492,557 109 1.7% $134,382,200 4.1% Tonawanda (T) 23,999 $14,694,684,404 631 2.6% $1,183,390,054 8.1% Wales (T) 1,923 $833,853,270 40 2.1% $23,157,231 2.8% West Seneca (T) 17,970 $9,583,482,689 4,118 22.9% $1,810,406,742 18.9% Williamsville (V) 2,057 $1,126,868,443 114 5.5% $35,127,170 3.1% Erie County Total 360,925 $222,515,035,436 48,045 13.3% $29,743,441,914 13.4%

Source: Erie County GIS 2020; RS Means 2020; USDA/NRCS 2019 Notes: RCV = Total replacement cost value (structure and contents) T = Town, V = Village, C = City, % = percent * Cattaraugus Tribal Territory and Tonawanda Tribal Territory were not included in the above totals, as the two tribes did not participate in this HMP update.

Impact on Critical Facilities

Approximately 11.3 percent of the critical facilities in Erie County are considered exposed to the expansive soils hazard area. Of the 474 critical facilities in the county exposed to expansive soils, 441 are considered lifelines. Table 5.4.4-6. summarizes the number of critical facilities by type per jurisdiction in Erie County located on expansive soil hazard areas. Table 5.4.4-7 summarizes the number of critical facilities exposed to the expansive soil hazard area by FEMA’s lifeline categories. Table 5.4.4-8. summarizes the type of critical facilities exposed to expansive soils. Bridges, hazardous material sites, and secondary education locations are the three types of critical facilities that are the most exposed.



Table 5.4.4-6. Critical Facilities Located on Expansive Soils

Jurisdiction

Total Critical Facilities

Located in Jurisdiction

Total Lifelines Located in

Jurisdiction

Number of Critical Facilities and Lifeline Facilities in Expansive Soils

Critical Facilities

Percent of Total Critical

Facilities Lifelines

Percent of Total

Lifelines Akron (V) 30 26 0 0.0% 0 0.0% Alden (T) 76 68 6 7.9% 4 5.9% Alden (V) 19 17 1 5.3% 1 5.9% Amherst (T) 391 387 98 25.1% 97 25.1% Angola (V) 20 18 0 0.0% 0 0.0% Aurora (T) 95 81 14 14.7% 12 14.8% Blasdell (V) 22 22 2 9.1% 2 9.1% Boston (T) 81 75 6 7.4% 5 6.7% Brant (T) 39 39 2 5.1% 2 5.1% Buffalo (C) 751 748 5 0.7% 5 0.7% Cheektowaga (T) 224 221 27 12.1% 27 12.2% Clarence (T) 121 115 26 21.5% 25 21.7% Colden (T) 67 56 3 4.5% 3 5.4% Collins (T) 71 55 6 8.5% 6 10.9% Concord (T) 84 68 8 9.5% 7 10.3% Depew (V) 63 63 12 19.0% 12 19.0% East Aurora (V) 42 41 4 9.5% 4 9.8% Eden (T) 78 72 9 11.5% 9 12.5% Elma (T) 83 75 5 6.0% 4 5.3% Evans (T) 112 109 11 9.8% 10 9.2% Farnham (V) 10 10 0 0.0% 0 0.0% Gowanda (V) 7 7 0 0.0% 0 0.0% Grand Island (T) 69 66 41 59.4% 38 57.6% Hamburg (T) 189 181 48 25.4% 47 26.0% Hamburg (V) 27 23 1 3.7% 0 0.0% Holland (T) 90 70 9 10.0% 4 5.7% Kenmore (V) 14 13 0 0.0% 0 0.0% Lackawanna (C) 94 93 0 0.0% 0 0.0% Lancaster (T) 109 103 25 22.9% 22 21.4% Lancaster (V) 58 53 23 39.7% 21 39.6% Marilla (T) 48 37 0 0.0% 0 0.0% Newstead (T) 64 61 0 0.0% 0 0.0% North Collins (T) 69 56 5 7.2% 3 5.4% North Collins (V) 14 13 0 0.0% 0 0.0% Orchard Park (T) 141 129 15 10.6% 14 10.9% Orchard Park (V) 21 18 0 0.0% 0 0.0% Sardinia (T) 78 57 3 3.8% 0 0.0% Sloan (V) 8 8 0 0.0% 0 0.0% Springville (V) 35 32 2 5.7% 1 3.1% Tonawanda (C) 61 60 1 1.6% 1 1.7% Tonawanda (T) 266 265 36 13.5% 36 13.6% Wales (T) 82 68 4 4.9% 3 4.4% West Seneca (T) 145 140 16 11.0% 16 11.4% Williamsville (V) 16 14 0 0.0% 0 0.0% Erie County Total 4,184 3,933 474 11.3% 441 11.2%

Source: Erie County GIS 2020; USDA/NRCS 2019 T = Town, V = Village, C = City, % = percent * Cattaraugus Tribal Territory and Tonawanda Tribal Territory were not included in the above totals, as the two tribes did not participate in this HMP update.



Table 5.4.4-7. Number of Lifelines Located on Expansive Soils

Lifeline Categories Total Lifelines in

the County Expansive Soils

Exposure Communication 126 0

Energy 397 3 Food, Water, Shelter 1,458 1 Health and Medical 1,081 1 Safety and Security 1,956 0

Transportation 3,099 1 Total 8,117 6

Source: Erie County GIS 2020; FEMA 2020; USDA/NRCS 2019



Table 5.4.4-8. Critical Facility Types Located on Expansive Soils

Jurisdiction

Critical Facilities Exposed to Moderate Expansive Soils

Air

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Air

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Run

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Bri

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Com

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Fac

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Dam

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Sta

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Fire

Sta

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Haz

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Hig

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Gar

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Lib

rary

Nat

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Gas

Fac

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Oil

Faci

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Post

Off

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Prim

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Akron (V) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Alden (T) 0 0 0 0 0 0 2 0 0 0 0 0 0 0 0 0 0 0 0 4 0 0 0 0 0 0 0 Alden (V) 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Amherst (T) 0 0 17 0 3 0 1 2 6 7 0 0 0 0 0 3 0 0 0 0 5 51 0 3 0 0 0 Angola (V) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Aurora (T) 0 0 4 0 0 0 2 0 0 0 1 0 0 0 0 0 0 0 0 5 0 0 0 0 0 0 2 Blasdell (V) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 0 0 0 0 0 0 0 Boston (T) 0 0 2 0 0 0 1 1 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 1 0 0 0 Brant (T) 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 Buffalo (C) 0 0 3 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 1 0 0 0 0 0 0 Cheektowaga (T) 0 0 6 1 0 1 0 1 4 8 0 0 0 0 1 0 0 0 0 0 2 0 1 2 0 0 0 Clarence (T) 0 0 3 0 1 0 0 0 0 6 0 1 0 1 0 1 0 0 0 5 2 0 0 2 1 0 3 Colden (T) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 2 0 0 0 0 0 0 0 Collins (T) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 3 1 0 0 1 0 0 0 Concord (T) 0 0 2 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 5 0 0 0 0 0 0 0 Depew (V) 0 0 4 0 0 0 0 0 0 7 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 East Aurora (V) 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 2 Eden (T) 0 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 3 0 0 1 0 0 2 Elma (T) 0 0 1 0 0 0 1 1 0 0 0 0 0 0 0 0 0 2 0 0 0 0 0 0 0 0 0 Evans (T) 0 0 5 0 0 0 1 0 2 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 2 Farnham (V) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Gowanda (V) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Grand Island (T) 0 0 9 0 1 0 2 1 2 11 0 1 0 0 0 0 1 0 0 2 6 0 2 2 0 1 0 Hamburg (T) 0 0 16 0 1 0 1 0 1 10 0 0 0 0 0 1 1 0 0 0 7 0 0 0 0 0 10 Hamburg (V) 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Holland (T) 0 0 0 0 0 0 5 0 0 0 0 0 0 0 0 0 3 0 0 1 0 0 0 0 0 0 0 Kenmore (V) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Lackawanna (C) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0



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Lancaster (T) 1 2 3 0 2 0 3 0 1 6 0 0 0 0 0 0 3 0 0 1 0 0 0 0 0 0 3 Lancaster (V) 0 0 0 0 2 1 2 2 1 6 1 1 0 0 0 1 0 0 0 0 1 0 0 2 2 1 0 Marilla (T) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Newstead (T) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 North Collins (T) 0 0 0 0 0 0 2 0 0 0 0 0 0 0 0 0 0 0 0 3 0 0 0 0 0 0 0 North Collins (V) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Orchard Park (T) 0 0 5 0 0 0 1 0 2 1 0 0 0 0 0 0 0 1 1 1 2 0 0 0 0 0 1 Orchard Park (V) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Sardinia (T) 0 0 0 0 0 0 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Sloan (V) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Springville (V) 0 0 0 0 0 0 1 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Tonawanda (C) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 Tonawanda (T) 0 0 12 0 0 0 0 5 0 12 0 0 1 3 0 0 1 0 0 0 1 0 1 0 0 0 0 Wales (T) 0 0 1 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 2 0 0 0 0 0 0 0 West Seneca (T) 0 0 6 0 0 0 0 0 4 1 0 0 0 0 0 0 0 0 0 1 0 0 0 2 0 0 2 Williamsville (V) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Erie County Total 1 2 10

1 1 10 3 31 13 24 75 4 3 1 4 1 9 12 3 1 39 32 51 4 16 4 2 27

Source: Erie County GIS 2020; USDA/NRCS 2019 T = Town, V = Village, C = City, % = percent * Cattaraugus Tribal Territory and Tonawanda Tribal Territory were not included in the above totals, as the two tribes did not participate in this HMP update.



Critical facilities will experience similar impacts from expansive soils as highlighted in the general building stock section. Smaller structures built on expansive soils may be more susceptible to damages caused by the shrinking and swelling properties of expansive soils. Furthermore, roadways built on expansive soils that are major transportation routes leading to critical facilities or connect essential services to the community could also be affected. Roadways that become damaged from expansive soils could create a disruption to critical services. There are 892.1 miles of roadway exposed to the expansive soil hazard area out of a total of 5,818 miles of evacuation routes in the county.

Impact on the Economy

Expansive soils may impact the economy where structures and roadways are damaged. Businesses built on the hazard area may need to shut down for repairs or move to a new, potentially less profitable, location if the building does not meet the 2012 IBC code (FEMA n.d.). As discussed earlier, expansive soils may also cause damage to highways and roads. Damages result from differential vertical movement that occurs as clay moisture content adjusts to the changed environment. For pavement, differential movement of 0.4 inches with a horizontal distance of 20 feet can pose an engineering problem for fast travel (FEMA 1997). Infrastructure damage is costly and can impact the local and regional economy.

Impact on the Environment

As discussed in earlier sections, expansive soils shrink and swell based on available water content. Absorbing available water could reduce water availability for surrounding ecosystems. Shrinking soils from a lack of water could create cracks in the ground, impacted rooted plants. The instability of this soil type may not be the most ideal habitat for species in the county.

Cascading Impacts to Other Hazards

There are no known cascading impacts expansive soils cause to other hazards of concern for the county.

Future Changes That May Impact Vulnerability

Understanding future changes that impact vulnerability in the county can assist in planning for future development and ensuring that appropriate mitigation, planning, and preparedness measures are in place. Any areas of growth in the three jurisdictions where expansive soils exist could potentially be impacted by this hazard.

Projected Development

As discussed in Section 4, areas targeted for future growth and development have been identified across Erie County. The county areas targeted for potential future growth and development in the next five years have been identified across the county at the municipal level.

New development projects within the county will be advised to follow the 2012 IBC requirements (FEMA n.d.). The 2012 IBC requires that geotechnical investigations are conducted if expansive soils are likely to be present. Subsurface testing includes boring, creating test pits, soil sampling, and laboratory tests. If an expansive soil is present, it is recommended that development does not occur.

Projected Changes in Population

According to the U.S. Census Bureau, the population in Erie County has remained stable between 2010 and 2019 (919,040 persons in 2010 and 919,355 persons in 2019). Estimated population projections provided by the Cornell Program on Applied Demographics indicate that the county’s population will increase into 2040, bringing total population to approximately 945,891 persons (Cornell Program on Applied Demographics 2017).



More housing units in the jurisdictions most vulnerable to expansive soil impacts suggests that a greater number of persons will be at risk of being exposed to expansive soil hazard areas.

Climate Change

Most studies project that the State of New York will see an increase in average annual temperatures. Additionally, the state is projected to experience more frequent droughts, which may affect the availability of water supplies, primarily placing an increased stress on the population and their available potable water. A decrease in water supply or increase in water supply demand may increase the county’s vulnerability to expansive soil impacts. Critical water-related service sectors may need to adjust management practices and actively manage resources to accommodate for future changes.

Vulnerability Change Since the 2015 HMP

Since the 2015 HMP analysis, population statistics have been updated using the 5-Year 2015–2019 American Community Survey Population Estimates (American Community Survey 2019). The general building stock was also established using RS Means 2020 building valuations that estimated RCV for each building in the inventory. Additionally, a critical facility dataset was provided from the county. The most significant change is that a quantitative analysis was complete for the county using soils data from USGS/NRCS.

Documents

Section 5.4.4 - Expansive Soils