Pierce County's education network was analyzed of its land use footprint to investigate facility sites contribution to impervious surface area (ISA) coverage in the region.  To limit the scope of this analysis, the school system (1) was queried and limited to elementary schools and private institutions omitted.  Points where designated as either urban or non-urban based on the condition of falling within the Urban Area Cluster (UAC) established by sourced through the US census (2).

 

Method:

By restricting UAC (3) to the routine Pierce County base map with Pierce H2o dissolved extent, an index of school grounds was established with a binary key (0,1) and further exported as elementary types in an added feature dataset.  Based on shape area (acre) sites were classified as in a relative scale (Small – Large) with an inverted heat ramp.  An extraction by mask was performed to isolate pierce county ISA (2) and school grounds points where joined as polygons expressing designated footprint (ground) that contained a percentage of ISA coverage.  Similar to the relative size key established previously, a scale of coverage is provided to show impervious coverage relational to footprint size by analyzing though the zonal statistics tool.  To provide a visual reference to the general size of elementary schools, a proximity to grounds was generated in the creation of Thiessen polygons.

   

Discussion:

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Of the 135 public elementary schools in Pierce county, the mean size was 10.19 acres with 1.84-5.29 acres occupied by the smallest (27) schools and 13.90-45.95 acres occupied by the largest (28) in the county with 122 existing in the designated urban cluster.  Zonal statistics of impervious surface land data provided from the MRLC (3) showed elementary school grounds land possessing on average 7.2% ISA in which groupings where established to designate low/med/high ranks by % covered.

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Further examination of ISA reveals a mean coverage of 7.8% over a mean footprint of 9.97 acres of elementary sites in urban clusters, and 4.76% of 12.31 acres of footprint of schools in non-urban clusters.  ISA 1 with 27% of all queries breaks down to 17% and 10% Urban/Non-Urban respectively, and ISA 3 with 56% of all queries breaks down to 54% and 2% in the same abstraction.