7100 HARDESON RD 2016-01-01 MF Import

Fisher S Sons, Inc. JN 97282 August 19, 7997 Page 2 soil appears to be fill, although the fili coutd extend to 20 feet. In Boring 4, similar soils were encountered, with standard penetration blow counts, even in the nearvsurtace soils varying from 25 to 50 blows per foot. Borings 2 and 3 were drilled on the southwest and southeast building comers, respectively. These borings encountered looser fill soils near the ground surtace. The penetration of blow counts at 5 foot in Boring 2 were 9 blows per foot, and in Boring 3, 16 blows per foot. The fili and native soil below a depth of about 8 feet was relativeiy dense. The nati:re soils are gray gravelly sands that have been glacially conso��dated. Similar soil con�itions we�B found in two previous test borings conducted near the proposed building. The final logs represent our interpretations of the field togs. The straGfication lines on the logs represent the approximate boundaries belween soil types at the exploration Iocations. The actual transition between soil types may be gradual, and subsurface conditions can vary between exploration locations. The logs provide specific subsurface information only at the locations tested. If a transition in soil type occurred belween samples in the borings, the depth of the transition was interpreted. It was very difficult in several of the boring locations to deiineate the fili from the native soils based on the limited size of the sampies. The relative densities and moisture descriptions indicated on the test boring logs are interpretive descriptions based on the conditions observed during drilling. Groundwater Groundwater seepage was encountered within the naGve sands at a depth of 20 to 25 feet belc..r the ground surface. Because this seepage was observed in relaUvely clean sands, we anUcipate that a significant amount of deep groundwater is likely present. The test borings were left open for only a short time period. Therefore, the seepage levels on the logs represent the location of transient water seepage and may not indicate the static groundwater Ievel. It should be noted that groundwater Ieveis vary seasonally with rainfall and other factors. CONCIUSIONS AND RECOMMENDATIONS General There ar� several foundation altematives that could be used for the construction of this building. We considered the use of concrete drilled piers, however, the presence of groundwater would cause caving in an open drilled pier hole. Therefore, the only economical way of constructing concrete piers would be to utilize the augercast method. Augercast piers would limit buiiding settlement. The piers would have a relatively high load-bearing capaciry and would be on the order of 25 to 30 feet in length. The existing community transit building to the north was preloaded prior to its construction. The preload was conducted because a portion of the building was placed over an old detention pond that had been filled with relatively sok silty soils. It is our opinion that a preload is not practicai at the subject building location. Because the fill soils are moderately dense and granular, we anticipate that the consolidation achieved from a preload would be relatively minimal. The type of settlement that will occur under the building will be long term, since the fill soils are unsaturated. Foliowing initial primary consolidation under the new loads, foundation settlement will take place siowly over a period of at least 10 to 20 years, as soil creep occurs and as groundwater conditions change. If long-tertn total settlements on the order of GEOTECH CONSULTA1vT5. I� iC.