13 - RESOLUTION ADOPTING THE 2017 LAMAR COUNTY MITIGATION PLAN

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Lamar County Multi- Jurisdictional Hazard Mitigation Plan Chapter Three 3. Extent The most extensive damage from expansive soils can occur to bridges, highways and streets. Homes, buildings and other structures can have extensive damage resulting in sticking doors, uneven floors and cracks in the foundation, floors, walls, and ceilings. The greatest damage occurs when structures are constructed when clays are dry (such as during a drought) and then subsequent soaking rains swell the clay. Damage can become so severe that the cost of repair can exceed the value of the building. Both public and private structures can develop extreme foundation problems during times of shrink -swell events. The most common signs of damage are cracks in foundations, brick exteriors, drywall interiors, sidewalks and other concrete structures within the building. Sewer and water lines are also affected by shrink swell soils. The action of the movement of the soils can snap water and sewer lines, producing a minimum of area discomfort, and a maximum of a serious health and welfare risk. 4. Previous Occurrences Since this hazard develops gradually and seldom presents a threat to life, problems may not be recognized as being related to expansive soils or may be considered only nuisances and therefore never repaired or reported. No records of specific incidences of structure loss due to expansive soils in Lamar County were found. 5. Probability of Future Events Since no records of specific incidences of loss associated with expansive soils were found and no specific areas of expansive soils were identified within the county, Probability of Future Events cannot be determined at this time. However, according to public opinion, the probability of future events of loss due to expansive soils within the county is possible. 6. Vulnerability The effects of expansive soils are most prevalent when periods of moderate to high precipitation are followed by drought and then again by periods of rainfall. Other cases of damage result from increases in moisture volume from such sources as broken or leaking water and sewer lines. Dry clays are capable of absorbing water and will increase in volume in an amount proportional to the amount of water absorbed. Areas capable of these changes in soil volume present a hazard to buildings, slabs, concrete, asphalt and other structures built over them and to the pipelines buried in them. Houses and one -story commercial buildings are more apt to be damaged by the expansion of swelling clays than are multi -story buildings, which are usually heavy enough to counter swelling pressures. However, if constructed on wet clay, multi -story buildings may also be damaged by clay shrinkage when moisture levels are substantially reduced. 141