2001 W MUKILTEO BLVD 2016-01-01 MF Import

Proposed McGbe Residence Remodel Everett, Washington Projcct No. 6G-9701022 Page 5 �� l \ � �p.-1\C.,� � � i� � ,� i� .� i� r � During the site reconc►aissence, xveral ceoent "tlow" W�dslides w�a�e obxrved on slopes adjacent to the developed pert of t6e siu. The flows generslly involved movement of shsllow tayers of s�uface soils a� a r�ult of satucation by surface and subsurfece wata. T6e largest of the raxnt sGda appeared to have ban triB6� P��Y bY a�uation of surfice soila, hovreva Poor drainaBe mw4eaKnt aed slope maeagement practioes weie probably coMributory ca�na. 7Le tvro largest alide aars hsd piles of yard wavte or other debcia nar their up-slope limib, which probsbly held �anificant surfsce water and enhanced suface weta in6ltration at the tops of the siidw. Additionelly, the lerger siide to the east of the house had occu�red where a drainage pipe from tLe developed pert of the site was draped over the siope and pafo� to allow disct�arge direcdy oato the alope. Sius such ag this one are espxially prone to flow feilures as a rault of reladvely looae gcanular soils located above more denx, siltier soils, in a sloping environnxnt. The body of stcuctural RU beneath the deck en�a and extax�ing to tLe south on the east side of the Iwuse (B-3) is petticularly suspxt becaus�e of the very low densiry, abundac�ce of perched water within the 611, exposiue of � soil conditions W slopes ranging from approximately 30 W 40 degras, and the surcharge caused by the fill geometry. Several soil, groundwater, and topogrephic condi6ons are present on titis aite thet create the potential for slope movement, and numerous mxnt 8ow failuns were noted. It does not �ppear thet any of the previous slope movert�n►ts have raulted in significaat dart�ege W the site improvements, however some slope debris &om the site may have been depositai on the reilroed grade to the noKh or in the crak bed to the east. In Gtles' opinion, the potential for future �tope movema�b aimiler to those tlut are already known must be considered high. [t would not be feasible, within a reasonable cost �nd effoK, to nmove all risks of future slope movement and all potendal for dart�ege w sioe improvea�enb. 'tikre are, however, numerous measures that can be readily ac:complished that would redua risks aignificandy. Ultimately, only the hommwner can dccide what level of risk is Wlerable, and wttere the belance betw�cee costs and benefits for risk reduction measures lies. This is a particulerly good time to conaida risk reduction measures, as a pact of planning for the remodeling of the residenee which eould inerease the potential risk exposure. The following improvements would reduce the potentiel for slope movemenb, and therefore risk of damage to site irnprovements as a rosult of slope movement. The rawmmmdadons are presented generally in order of decreasing effectiveness, though it sheuld be realiud that the admation of effectiveness of these measures is subjective and based on our experience with similer projxts: • Begin a rcgular program of inspcction, maintenance, end cepair of site drainage systems. Any drainage component that collects surface water could potendally leek, clog, or overflow, resulting in uncontrulled discharge in undesirable locadons. Inspecdon� should be pedormed et least once each fall beforc the winter raii►y season.