3315 BROADWAY 2017 HOPEWORKS STATION 2 Geotech Report 2022-10-25

HopeWorks Social Enterprises JN 17298 July 12, 2017 Page 5 dense soils and bracketed to the building foundations. Alternatively, narrow "slot-cuts" could be completed beneath the YWCA building footings to the proposed bottom-of-excavation depth on the subject site. The slot-cuts can then be formed and filled with concrete, extended the building loads downwards vertically such that the proposed excavation does not undermine the YWCA footings. The slot-cuts should be completed in horizontal sections no more than 5 feet in length. This underpinning program may be needed for the adjacent southern HopeWorks building once the depth of its footings is determined. Excavations taller than 10 feet are proposed along the western property line. If an excavation easement into Broadway Avenue cannot be obtained, temporary excavation shoring will be necessary along the western property line. We anticipate that cantilevered soldier piles will be the most appropriate shoring option considering the depth of excavation and the existing fill soils encountered upslope of the existing retaining walls. It appears the existing retaining walls will need to be removed prior to installing soldier piles due to the varying horizontal (east and west) alignment of the existing retaining walls.We recommend existing retaining walls be demolished in sections no longer that 10 feet in length. A berm of soil should be placed against the exposed section of soil at a 1:1 (H:V) inclination prior to continuing the next section of demolition. This is to provide adequate lateral support of the soil beneath the Broadway Avenue right-of-way until soldier pile shoring can be installed. The Temporary Shoring section contains an expanded discussion of cantilevered soldier piles. The onsite soils have a very low permeability due to their silty nature. Considering this, it is our opinion that infiltration of collected stormwater is not appropriate for the subject site. The erosion control measures needed during the site development will depend heavily on the weather conditions that are encountered. We anticipate that a silt fence will be needed around the downslope sides of any cleared areas. Existing pavements, ground cover, and landscaping should be left in place wherever possible to minimize the amount of exposed soil. Rocked staging areas and construction access roads should be provided to reduce the amount of soil or mud carried off the property by trucks and equipment. Wherever possible, the access roads should follow the alignment of planned pavements. Trucks should not be allowed to drive off of the rock-covered areas. Cut slopes and soil stockpiles should be covered with plastic during wet weather. Following clearing or rough grading, it may be necessary to mulch or hydroseed bare areas that will not be immediately covered with landscaping or an impervious surface. On most construction projects, it is necessary to periodically maintain or modify temporary erosion control measures to address specific site and weather conditions. The drainage and/or waterproofing recommendations presented in this report are intended only to prevent active seepage from flowing through concrete walls or slabs. Even in the absence of active seepage into and beneath structures, water vapor can migrate through walls, slabs, and floors from the surrounding soil, and can even be transmitted from slabs and foundation walls due to the concrete curing process. Water vapor also results from occupant uses, such as cooking and bathing. Excessive water vapor trapped within structures can result in a variety of undesirable conditions, including, but not limited to, moisture problems with flooring systems, excessively moist air within occupied areas, and the growth of molds, fungi, and other biological organisms that may be harmful to the health of the occupants. The designer or architect must consider the potential vapor sources and likely occupant uses, and provide sufficient ventilation, either passive or mechanical, to prevent a buildup of excessive water vapor within the planned structure. Geotech Consultants, Inc. should be allowed to review the final development plans to verify that the recommendations presented in this report are adequately addressed in the design. Such a plan GEOTECH CONSULTANTS,INC.