244 HEATHER RD 2016-01-01 MF Import

U'(^8/1597 1a:15 2U63659973 OTTEN ENGIP�EEF.IP:G PFGE E+5 Mazk T. Otten, P.E. Engineering Consultant Rockeries are suitable for wall up to 8 feet high,when flie rocks are supported by dcnse native soils end the soil behind the rockery is well drained. For your property, a rockcry 3 to 8 feet high could be built west of the concrete patio along the entire length of the house. Since a rockery must be suppoRed by dense soil,it would bc located near a line between Borings B-1 aud S-2, which are 5 to 10 feet west of the patio. A rockery would not be appropriate aton6 the west side of the yard because it would not be supported by dense notive soil and would npt provide support for the loose sand fill. I understand that you are pla�ming to install a french drain system on the east a�id norih sides uf' the house and wlll be replacing a portion of Uie concrete driveway. Control of roof runoff, driveway runoff,and shallow groundwater around die house will significa�ttly improve thc stability and are highly recommended. As we discussed,I recommend that the french drxiu be built along d�e entire east side of the yard and that two catch basins be installed in the low points of the concrote driveway to collect surface runoff and discherge it down tlie slope. To be most effective, the french drain should t>e built from the ground surface down the to top of hazd, low- penneability soils(or hardpan). The drain trenches should be backfilled with a free-draining gravel and should have a perforated pipe at least 4 inches in diameter. The discharge from the drains and from roof drains should be dischazged t�the creek in a solid pipe. In otder to proceed with final design and to confirm that the house is on dense soil, l recouunend that a geotechnical engineer or geologist observe soil conditions during construction of d�e fre�ich drain. At die same time, tlie backiiot stwuld be used to excavate test pits along the west side of the housc to conf"irm the depth of the hard native in the west yard. The test pits would be 5 to & feet deep a�id could be excavated with a backlioe. The Uniform Building Code requires a building permit for walls over 4 feet higl� and requires a grading permit for excavatians over a specified a�nount. I expected that Everett's ce.;es have similar requirements. It is commou that the pcm»t application will require a topog rapl�ic survey map of the house and yard area and a site plan that shows the property bowidaries. Summory Tn my opinion,the house a�id yard can be stabilized by controlling surface nuioff a�id sliallow groundwater around the house and by lowering the yard elevation. Alternatively,the yard could be stabilized at its cumnt ele��ation by controlling nuioff and cUnstntcting a structural soldier pile or tied-back wall: These actions are e!cpected to protect tUe house for a design life of 50 to 100 years. These actions would improve th� stability of the west slope, but are not expected to prevent funue surficiat soil movement on the undeveloped po�tion of the pr�perty. Sincerely, Mark T. Otten, P.E. 0725LTR�DOC 4 ��18/9�