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The unsuitable and unreliable soil must be replaced with structural backfill. This backfill must be <br /> placed up to the sub-grades of foundations and structures, floor slabs, pavements, and structural <br /> - fill features. The over.-excavation must be made sufficiently wide to accommodate structural <br /> backfill replacement. Structural backfill must extend laterally outward at least 2 feet from the above <br /> planned features. Structural backfill must slope downward 1:1 (horizontal:vertical) to the bottom of <br /> over-excavations. Where over-excavation is made in very soft soil, this slope must be 2:1 and <br /> structural backfill must extend laterally outward at least 5 feet from these above planned features. <br /> The material type and filling placement specifications for structural backfill must meet <br /> recommendations in the EXCAVATION AND EARTHWORK section of this report. Based on our <br /> experience with similar projects, either crushed limestone screenings (3/8ths inch to dust sized) or <br /> roadstone used by the Minnesota Department of Transportation (MNDOT) work well as structural <br /> backfill material. ' <br /> WATERPROOFING <br /> As stated in the GROUND WATER section of this report, we observed in-filled water Borings 1 and <br /> _ 2 at respective depths near 5 and 4 feet at the end of drilling. Levels of ground water and <br /> "perched" water at the project site will vary with climatic conditions (for example seasonal <br /> fluctuations in these levels and extended.periods of drought or excessive precipitation), surface <br /> water drainage, topography and site relief. <br /> Moisture in soil above ground water levels can migrate into building enclosures with no <br /> waterproofing protection. Migration occurs where soil contacts building surfaces. Architectural <br /> designs must include waterproofing and dampproofing to protect buildings against migration. <br /> Waterproof drains intercept ground water below building enclosures. Drains prevent ground water <br /> from entering building enclosures. Drains eliminate hydrostatic water pressure build-up along <br /> building surfaces. This pressure can produce excessive water seepage into building enclosures or <br /> — bouyant uplift of the building. Dampproofing must be applied on exterior surfaces of the building, <br /> to block capillary migration of soil moisture into the building. Waterproofing drains are installed <br /> below the building enclosure along exterior walls and under floor slabs. Waterproofing membranes <br /> are applied on exterior walls and floors of the building. Membranes must resist water infiltration <br /> caused by a maximum anticipated water pressure head. Membranes can be bentonite panels or <br /> bituminous mastic. Drain lines intercept ground water to prevent water from entering the building. <br /> Drain lines permanently lower ground water levels to drain line levels. Drain lines must be placed <br /> below floor slab levels along building exterior walls and possibly under floor slabs in poor-draining <br /> -- soil. Drain lines must gravity drain to sump pumps or storm drains properly sized to reliably <br /> discharge anticipated ground water seepage. Discharge can vary due to fluctuating ground water <br /> levels, soil type and drain line spacing. The drainage system designer must apply a proper safety <br /> factor against failure with respect to the subsurface area to be waterproofed. <br /> Drain lines must be perforated or slotted PVC pipe at least 4 inches in diameter. Lines.must be <br /> radially surrounded by at least 6 inches of clean free-draining granular material with less than 5 <br /> percent fines passing #200 sieve. The drain line pipe and granular material must be encased in <br /> filter fabric that prevents both "piping" erosion in surrounding soil and drain line clogging. <br /> Allied Project 04049 13 July 27, 2004 <br />