330 ELM ST VIEW RIDGE ESTATES 2022-04-04

« Geotechnical Engineering Evaluation NGA File No. 1085419 View Ridge Estates 330 Building Settlement March 22,2019 Everett,Washington Page 10 Drainage Improvements Surface Drainage: In general, the ground around the building should be regraded such that runoff is directed away from the building and collected in an appropriate stormwater collection system. Where possible, we suggest that the finished ground be sloped at a minimum gradient of three percent, for a distance of at least 10 feet away from the building. All surface water generated from paved areas and roof drains should be collected by permanent catch basins and drain lines, and be routed into an approved discharge system. No surface water should be allowed to flow towards the structure. Existing drains should be investigated and repaired, as needed, to ensure all runoff generated on this site is routed away from the building. Subsurface Drainage: During our site visit, we were unable to confirm the existence of a footing drain around the building. If it is determined that no foundation footing drains exist,we recommend that during the installation of the recommended foundation improvements an adequate foundation footing drain system be installed around the building. Footing drains should be installed at least six inches below bottom of the existing foundations. The drains should consist of a minimum 4-inch-diameter, rigid, slotted or perforated, PVC pipe surrounded by free-draining material wrapped in a filter fabric. We recommend that the free-draining material consist of an 18-inch-wide zone of clean (less than three- percent fines), granular material. Washed rock is an acceptable drain material. The free-draining material should extend up one foot below the finished surface. The top foot of backfill should consist of low permeability soil placed over plastic sheeting or building paper to minimize the migration of surface water or silt into the footing drain. Footing drains should discharge into tightlines leading to an approved collection and discharge point with convenient cleanouts to prolong the useful life of the drains. Roof drains should not be connected to wall or footing drains. CONSTRUCTION MONITORING We recommend that we be retained to provide construction monitoring services during foundation underpinning installation and drainage improvements to evaluate conditions encountered in the field with respect to anticipated conditions, to provide recommendations for design changes should the conditions differ from anticipated, and to evaluate whether construction activities comply with contract plans and specifications. \2�1 NELSON GEOTECHNICAL ASSOCIATES, INC.