Geology Task 2

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Western Governors University *

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Geology

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Jul 2, 2024

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Geology I: Physical Task 2: Mapping Michel E Deveau A.1. This task is a consideration of the Prentiss Woods as the site for a new 500 student, single story elementary school. A.2. Surficial and bedrock geologic maps are essential tools in construction when looking for possible school building sites. Bedrock geologic maps show the type and structure of solid rock that covers the surface or lies directly beneath the soil and vegetation. Knowing the type of bedrock is important for long term stability of structures. For instance, structures built over what is known as Karst topography jeopardize foundation integrity. Karst is formed when soluble bedrock such as limestone and gypsum suffer chemical weathering from groundwater, eventually forming fractures, caves and sinkholes (think Florida!). Bedrock geologic maps also show locations of any faults and folds, indicating fractured and weathered rock, not to mention possible earthquake activity. Bedrock maps indicate locations of aquifers, which are layers of underground rock formations that hold groundwater. Aquifers are an important source of water supply in urban areas. ( Reading Detailed Bedrock Geology Maps , 2016) Surficial geologic maps show deposits such as sand, gravel, clay, and other loose materials that overlie bedrock. Surficial materials are not soil types. They are an unconsolidated blanket of sediments produced because of weathering and erosion of the underlying bedrock. The surficial layer can go as deep as 1000 feet or be near non-existent over exposed bedrock. (Soller et al., 2009). Surficial geology maps are often best used in conjunction with related maps such as 1
significant sand and gravel and aquifer maps for complete information of what lies beneath the surface. For example, areas with significant sand and gravel can indicate better drainage for building home sites, whereas clay areas may be wetter. Clay areas may indicate possible swamp, or an area’s high susceptibility to erosion and landslides. Another advantage to using surficial maps is to assist in research for possible environmental concerns. Surficial materials tested for contaminants can indicate the nearby location of contamination sources such as landfills and underground storage tanks. ( Reading Surficial Geology 1:24,000-Scale Maps , 2012). A.3. Although most states have minimum recommendations for minimum size of elementary school sites (Maine is 5 acres), for this paper we will use a simple formula. According to GSE - Global Services in Education (2020), to determine total land area required we calculate the structure’s overall gross floor area (10m2 per student) and add it to the allocated outdoor area (10m2 per student). The calculations are as follows: GFA: 10m2 x 500 students = 5000m2 total Outdoor Area: 10mn2 x 500 students = 5000m2 Total minimum area required = 10000m2, or 107,640 feet, or 2 acres. I have selected 5 acres for building the new elementary school. This site is part of a 25.5-acre wooded area next to a newly constructed high school. Its location is at the edge of a growing suburb in east Bangor, with ongoing new home construction and an increasing population of young families. This means school accessibility will be within walking distance for many of the students. The forested site sits along an established public road. It has approximately 1000 feet of road front running east to west along Grandview Ave. Walking north from the road front, it has a 2
total 50-foot gain in elevation over a distance of 2000 feet before leveling off. The geologic maps indicate a surficial layer of forest duff (vegetative matter of a forest floor), over a layer of glacial till (glacial deposits), over bedrock. Overall, surficial depths in Maine are 50 feet or less. Specific testing will be required to know the depth to bedrock at this site (i.e. test borings, geophysical surveys) in order to determine if blasting will be required. ( Reading Detailed Bedrock Geology Maps , 2016). A.4. The geologic history recorded in Maine’s bedrock spans over 1 billion years and has been affected by several major cycles of deposition, deformation, and igneous activity. The Great Ice Age of the Pleistocene Epoch brought slow moving glacial ice across Maine. This glaciation lasted from 2.5 million to 10000 years ago. The glacier scraped away soil and loose debris down to the bed rock as it moved over the landscape , and then redistributed the sediment across the state. As it melted it dropped all that sediment material to cover Maine with a layer of glacial till. Glacial till, also called stony till, consists of unconsolidated material, essentially gravel, sand and rocks. Thanks to a warming climate 10000 to 15000 years ago, post glacial Maine was mainly forested much as it is to this day. ( Explore Maine Geology , 2012). This area has not suffered greatly from natural weathering and erosion. This area has continued to see spread of residential communities and shopping unaffected by natural geologic changes in landscape. However, recent flooding of nearby floodplains has caused careful planning as to where new construction be placed. (see next section) Maine has a history of seismic activity, although Maine earthquakes are mostly small in magnitude and often unnoticeable. The natural hazards of significance recently are related more 3
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