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Techmcal Requirements <br />CivO Engineering <br />Site soil stratigraphy generally consists of surficial topsoil with organics <br />overlaying silty and sandy clay till. The topsoil thickness ranges from O.T to <br />6' thick and is gener.\, quite soft The underlying till is soft to very stiff, <br />with the softer soils tending to be more prevalent in the east and south halves <br />of the site. Soil moisture content is generally high; four of the eight bonngs <br />exhibit free groundwater, probably representing a perched groundwater <br />Construction of the proposed ice arena will necessitate removal of all soft <br />soils and soils containing organics ft-om the proposed building area, includ­ <br />ing a perimeter oversize area. Building foundations shall penetrate to normal <br />frost depth and bear on firm to stiff till, or on granular structural fill placed <br />over the till and up to the underside of the building foundations. Building <br />floor areas will be simularly supported, except the initial layers of fill may be <br />compacted non-expansive clays from on-site, overlaid by compacted <br />granular soils. <br />Because the proposed parking lot area generally contains weak soil unable to <br />provide adequate support for pavements, a procedure of subgrade correction <br />will be required. While the weaker soils exist to depths of several feet, rather <br />than replace these soils totally, we propose that correction of subgrade be <br />limited to the upper 30" or so. and incorporate a geotextile fabric and <br />imported granular fill layer over the weak soils. This appproach will provide <br />reasonably competent subgradcs for pavement, but with higher than normal <br />settlement over time, and associated maintenance requirements. <br />The building location as presently depicted on the site plan honors a 50 <br />setback fnim both the west and north property lines. This location was <br />chosen for both design and economic reasons. In general, the better soils of <br />the site are closer to proposed design elevations at this location, thus requir­ <br />ing less subgrade correction for building foundation and floor support. <br />Further, the existing topography between the west property line and building <br />west face lends itself well to the design solution, resulung in less alteration of <br />existing grade and providing the opportunity to use -.nplace soils for suppport <br />of interior seating. . , u <br />Other building location options that would honor a 100’ setback from the <br />west property line would increase cost significanUy. primarily due to a much <br />greater subgrade correction requirement. Further, because Minnehaha Creek <br />Watershed District requires treatment of stormwater before discharge off-aite, <br />a so-ategically place wet basin is required. Honoring a 100’ building seback <br />from the west property line would likely result in a visually tortured soluuon <br />to wet basin design. <br />Storm sewerage in the site vicinity is limited to culverts and ditches, gener ­ <br />ally associated with rural roadway sections. However, because the site ;^ea <br />is within the Minnehaha Creek Watershed District, we must respond to their <br />criteria regarding discharge rate and storm water quality. Accordingly, <br />management of storm water discharge rate will require temporary inundauon <br />GEOTECHNICAL <br />BUILDING LOCATION <br />STORM se\vt :rage <br />tra /hga /ka <br />Orono Ice Arena