Laserfiche WebLink
AMERICAN ENGINEERING TESTING, INC. AET Project No. 22-00012 <br /> We recommend that you plan the construction schedule to accommodate a minimum 30 day <br /> waiting period between the completion of site grading in the building pad, and the start of <br /> footing construction. If the construction schedule cannot accommodate this waiting period, then <br /> we strongly recommend that you authorize us to complete a supplemental field and laboratory <br /> testing program to further assess the potential settlement, and evaluate potential alternative site <br /> preparation methods. <br /> If there is space on the site to open a borrow pit, some of the on-site clay, silty sand, and sand <br /> might be reusable as fill in the building pads. Much of the on-site cohesive soils have elevated <br /> water contents, up to 41% at our borings; we estimate that the optimum water content is about <br /> 16% to 18%, based on the Standard Proctor test (ASTM: D 698), and soils with water contents <br /> above about 18% to 20% would require drying before use as compacted fill. Cohesive soils used <br /> as backfill must be dried to within 2% of the optimum water content before placement or treated <br /> with Class C fly ash or hydrated lime to achieve the desired compaction with reasonable effort <br /> and without drying. However, lime or fly ash treatment requires that the soil temperature be no <br /> lower than about 45°F at the time of treatment. It is beyond our scope of services to calculate the <br /> amount of suitable fill that might be available on the site. <br /> For imported fill in the building pads, we recommend using a granular soil with less than 12% <br /> passing the No. 200 sieve, such as Mn/DOT 3149.2B2 having no gravel larger than 3 inches. <br /> Alternatively,a lean clay(USCS Classification of CL or CL-ML), clayey sand(SC), or silty sand <br /> (SM) could be used. If the contractor proposes a different type of fill, a sample should be <br /> submitted to our laboratory for testing and review by a Geotechnical Engineer. <br /> The use of sand fill may be advantageous since the initial lift can be placed in a thicker lift than <br /> clay, while still achieving compaction. This would reduce the potential for disturbing the <br /> excavation base. Furthermore, there are several risks associated with using the on-site clay or <br /> imported silty/clayey soils as fill. Wet weather can increase the water content of the clay and <br /> require drying before it is used as compacted fill; this could significantly delay construction. If <br /> Page 12 of 28 <br />