1517 132ND ST SE 2024-12-09 - Laserfiche WebLink

Proposal for Geotechnical Engineering Services Proposed Bank: 1515 132nd Street Southeast, Everett, Washington March 15, 2019 approximate. The following is a generalized description of the soils encountered in the borings. Asphalt: All of our borings were located in asphalt pavement parking and drive areas. At our boring locations,we encountered four inches of asphalt surfacing. Fill: Below the asphalt, we encountered a surficial layer of fill. The fill generally consisted of sandy silt and silty sand with varying amounts of gravel and cobbles. The fill ranged from 3 to 41/2 feet thick and was characterized by the presence of trace amounts of organics, filter fabric, and charcoal seams. The approximate fill thickness is identified on the boring logs and on Figure 2. Vashon Till (Qvt): The native soil below the fill consists of medium dense to very dense silty fine to medium sand with gravel and sandy silt which we classified as Vashon Till. The till graded to dense to very dense at 3 to 7 below grade. Increased moisture was encountered in this unit at 7 to I I1/2 feet below grade in this unit. The Vashon till encountered at our boring locations is consistent with the geologic mapping. All of our borings were terminated in till. Our subsurface descriptions are based on the conditions encountered at the time of our exploration. Soil conditions between our exploration locations may vary from those encountered. The nature and extent of variations between our exploratory locations may not become evident until construction. If variations do appear, PanGEO should be requested to reevaluate the recommendations in this report and to modify or verify them in writing prior to proceeding with earthwork and construction. 3.4 GROUNDWATER Increased soil moisture and light groundwater seepage was encountered at 7 to 111/2 feet below grade at the time of drilling. This moisture is likely perched groundwater that has developed in lenses of more permeable soil within the till formation and may be related to the stormwater retention pond located to the east of the site. If seepage is encountered, we anticipate seepage rates will be light to moderate. Groundwater levels will change depending on the season, amount of rainfall, surface water runoff, and other factors. Generally,the water level is higher and seepage rates are greater in the wetter, winter months (typically October through May). During periods of significant precipitation, perched groundwater may also be present at the fill-till contacts. 19-049 1515 132nd St SE Page 4 PanGEO,Inc.