1621 ENGLAND AVE 2016-01-01 MF Import

1'ebruary 27. 2U09 Sultnn Crossing I.&A Job No. 9A008 Pagc 3 emcrging water can crodc lhe soils in the scepage zonc and cause thc ovcrlying soils to slough and slide. The Whidbcy formation deposits in their undisturbed nati��e state are capablc of providin�good foundation support to structures. CALISG OF CONCRG'1'F. PIER TILTING 13aseu on mtd gcologic and soil conditions indicated on the above-referenced geologic map and our cxperience in the ncighborhood of the subject residencc, we belicvc the surficial soil unit at the subject residencc site is consisted of Gsperancc s,nd deposits. The back (northern portion) of thc site over which the deck is locatcd is likcly manticJ by a luyer of loose sand oC cither sloughed-off and red��posited soils or of loose fill pushed over the original slope during gmding of thc resiJcnce �i!�•. Somc of tlic concrete piers supporiing the deck arc likely not seated dceply cr.ough into the. underlying dcnsc sand soils. Thc laycr oC loosc surticial sand soils woulJ creep slowly downhill during extended hcavy rainstomis or strong carihquakcs and, therefore, causing the insufficienUy embedded concrete picrs to lean dotvnhill. 'fhe movement of thcse concrete piers would then kick thc hottom of the deck timher outward. The above arc the causes wc belicvc havc caused somc of thc concrete picrs supporting lhe deck to Ican outward. RGMEUIr�I. RGCOMM11I'sNUAT10NS The tilted concrcte picrs should be strengthened for their vertical bearing capacity as well as laterul load resistance. To achicve bod�, our rccommendations :ue sho�vn on 1'late 1 attached hereto. A pit shoufd bc excavated in Gont of the concrete piers to be strengthcned to get sufficicnt exposure of the embedded portion of thc picrs for construction work. A 2-inch stecl pipe pile (Schedule 80, 2.375-inch outside diameter x 0.218-inch wall) should be driven into the ground next to and in front of the cach concrete �,ier to be strcngilicned. The stccl pipe pilcs should bc driven to into thc unclerlying dense sand with a 90-pound pneumatic jackhammer to a rclusal defincd as "no more than onc inch of pcnetration I�;r 60 seconds of continuous driving". LIU & ,�►SSOCIATES, INC. 3�5