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Home My WebLink About965000348 Geotech Assessmento~- ~~~ STRATUM GROUP 1451 Grant Street, Bellingham, WA 98225 Phone (360) 714-9409 Apri128, 2008 Dave Goldsmith 536 Foster Street Port Townsend, WA 98368 Re: Geology Evaluation Proposed tree removal and tree trimming Bluffs Drive, Kala Point Dear Mr. Goldsmith: ~~~~~~~ r~~sf - 6 ~ooa ~5 ~~'i~`~f DAD W a tme.~. a uVt3i11 Stratum Group visited the proposed tree removal sites along the shoreline bluff at Kala Point. The purpose of our visit was to determine if proposed tree removal and proposed tree trimming would have a potential negative impact on slope stability. at Kala Point. The trees in question are located on the slope down slope from Bluffs Drive. We visited the shoreline bluff at Kala Point in March 2008 to evaluate bluff conditions, slope failure processes and to assess the role of the trees proposed for removal or trimming on the bluff stability. The locations of the trees in question were provided to us at the time of our site visit as well as via photographs of the trees provided to us. The photographs were taken from the back. yards of a condominium unit at 121-1 Bluffs Drive. This report provides an overview of the geology conditions of the bluff, erosion and landslide processes at the bluff and an evaluation of the role of trees relative to erosion and slope stability at this bluff site. GENERAL GEOLOGY Northwestern Washington has been occupied by continental-glaciers at least four times during the Pleistocene Epoch (1.6 million to 10,000 years ago).. During these glacial and accompanying interglacial periods, the underlying bedrock was eroded and a relatively thick layer of glacial related and interglacial fluvial sediments were deposited over the underlying bedrock in the vicinity of the subject property. The Surficial Geolo ig c Map of the Port Townsend 30- by 60-Minute Quadrangle, Puget Sound Region, Washington (Pessl, Dethier, Booth and Minard, 1989) and the Geolo imp of Northeastern Jefferson County, Washin tg_on (Birdseye, 1976) indicate the shoreline and bluff exposed on the bluff is underlain glacial till and advanced outwash deposits. The glacial till is described as consisting of a mixture of clay, silt, sand and gravel and is in a very compact condition. The advance outwash deposits consist of sand, gravel, silt and clay deposited by meltwater flowing from the advancing Puget lobe of the Fraser glaciation. The advance outwash Apri128, 2008 ~~~ o ~ 2~~8 Kala Point Bluff Tree Removal and Trimming Geology Evaluation sediments have been overridden and consolidated by glacial ice. ~' '`i' '`" Observations of the bluff face slopes and upland areas are consistent with the mapping described above. Glacial till at the top of the shoreline bluff at-the northwest end of the bluff along the Kala Point development and on the bluff at the -State Park. The till thins towards the southwest and is not present at the top of the bluff in the area where trees, are proposed to be removed and trimmed. The advance outwash deposits on the bluff consist primarily of sand with occasional lenses of. gravel and silt. The sediment generally grades coarser from the lower slopes of the bluff towards the upper slopes. This is consistent with the' unit being advance outwash (the coarser material being the result of the glacial ice front getting closer). Much of the sand lacks clay and as such lacks cohesion even though it has been highly compacted by the over ridding glacial ice. The lower. slopes may transition into preglacial deposits; however, no very old pre glacial deposits were observed on the lower slopes of the area below where trees -are proposed to be removed or trimmed. The base of the- bluff below the proposed tree removal and trimming area is underlain by early. advance outwash sand and gravel. SPECIFIC SITE OBSERVATIONS The shoreline bluff in the vicinity of the proposed tree removal and trimming area is approximately 120 feet high. The slope is fairly plainer and is covered with salal, ferns and evergreen huckleberry as well as second growth Douglas fir. The slope is approximately 35 degrees. -The base of the slope ends at a backwater wetland area behind a barrier beach. As such, there has been no erosion along the base of this section of bluff as it is protected by the beach in front of it. No areas of recent landslides are evident on the slope. No wet areas were present. The slope appears to be stable under current conditions. CONCLUSIONS Five trees are proposed to be removed and five trees are proposed to be limbed for view purposes. Based on the stable slope condition and well vegetated nature of the slope, the removal and limbing of trees as proposed will not have a negative impact on slope stability. Enough other trees are present and are spaced in a manner that no significant loss of root cohesion is anticipated on the slope. The presence of a very health understory of salal and evergreen huckleberry will also provide plenty of root cohesion. The canopy of trees will be left Stratum Group File:2.2.08 2 Apri128, 2008 Kala Point Bluff Tree Removal and Trimming Geology Evaluation in tact well enough that I do not anticipate that this will create any opportunity for invasive less desirable plants on the slope. The base of the bluff is not subject to erosion at this location due to the barrier beach. Hence large woody debris recruitment to provide natural shoreline armoring protection is not an issue at this section of bluff. Even then, the proposed tree removal is no more than a thinning and would not substantially impact large woody debris availability over time as the remaining trees will be more optimally situated for growth. Stratum Group appreciates the opportunity to be of service to you. Should you Have any questions please contact our office at (360) 714-9409. Sincerely yours, Stratum Group ~.., Dan McShane, M.Sc., L.E.G. Licensed Engineering Geologist ~~ ~~ p~~ M~~ - 6 2QQ8 w ~..::~ ~~~~~$~ ~° BCD Stratum Group File:2.2.08 3 _,- ,~ ~~ I ~.r - ~~~~ - ~' ~a~r ~ ,- r `t ., ~} ~1 '~ ~~~µ~p~ 1 ~~~~I~~~~ is i.~ Vrl R - ~ ~~~V .. t~ E6.E h~L+'e`~ii U~Y' ` A" "` 4 ti ~~ -.~ s~ t~ ~, °~: fS .~ '"RSi s V U ~~ !2 N +~ ~-1 N ~1 ~ ~ g 3 -i-) a n•( O N 0 ~V x t ~ m°O `~ am~ •~~__ ~. ~krtisfi: ~:.t ?~.s~ I ~ ~w:~ ~ ~ ~ ~r~ :~~3 ~ I ~ I ~~ ~ ~ ~ ~ ~~ x I I ~S~ ~~ ~ ~' ~ --~ y I~6 13is~ TREE ACTIONS-Bish 121-1 Bluffs Dr. h:360 385 0635 and c:360 774 0830 rbishna.uvic.ca Trees 1-8 are all directly in.front of the 121 building. Tree 10 is just slightly to the right. and tree 11 is just slightly to the left facing the water. The major problem is that after some limb removal years ago the bottom limbs on most of these trees have grown and sagged sufficiently to cut off major marine views, especially of Mt. Baker. This is now clregear since three trees below the slope were topped and their interference with views re,}~o ~, ~ ~~ uirements to restore the views are: / ~, TREES BY NUMBER as indicated on sketch plan All appear to be Douglas Fir ~ _ 6 2~0~ No action required: Tree No. 1 (it is numbered so all trees in the area are identified) Limb removal, approximately 6' but hazd to judge as limbs aze hard to distinguish from the g~oand ~'~ ~"~ ~ Trees #2, 3,~ 5, 8 and 9. 't Chrr..~q~ }~ f"~.t3vrr.~ 1~cE~c.:..cs ~ ~^~ Se~~ , d? tz`~ ~~/G~ I think all except Number 9 can be climbed without spikes. There are two kinds of spikes. The traditional wide relatively shallow ones that are associated with traditional logging and a narrower sharp spike that makes a smaller hole. Anderson Tree service recommends the narrower sharp spike for reduced damage although even they do not feel spike use on a tree that has not been climbed recently is really damaging to the tree. (The topper climbing without spikes to do the topping fell once from about 15' but the brush was think enough to prevent injury) . Tree removal -Number 7 has branches which block views and it is falling over; supported only by branches on an adjacent tree. It is unsafe to climb and should be cut off before all roots are raised out of the soil when it finally falls. Tree removal -Number 6. This tree is too thin to climb but still has some branches in the way. Tree removal -Number 10, this is a very thin tree that cannot be climbed and it blocks the view of the Glacier Peak area. Tree removal -number 11, this is not a healthy tree. Its needles are sparse and off color and will eventually block views as it grows taller. These actions will not restore the views that were present when the condo was constructed but they will open up the most important views and leave trees to frame those views. All of these trees have significant tops that block views from condo's behind but unless those residents request view restoration removing limbs is fine with us. LOCATION Tree Number 1 is a little less than 20' from the edge of the deck in front of 121-1. All except Number 11 are in the top third of the slope and a couple hundred feet from the beach itself. Number 11 is closer to the wet area below the slope but a little further back than the three trees that were previously topped. The entire slope is fully vegetated and there are no stability problems. -~ -~ - -~ -: ~ - -- --, NOV 1 fi 20Q7 ~- - ~ ~ ~ \ y ~1;} .. .~ ~ J ~; ~~:~ A i y .~.. <- r P ~ M1 ,~ t T ~~ a `Cl eZ ~ "' .. f ~. is T 1'. ~ Ji ~. .c l" r ~~ !"' ~' g{ O ~ ` T F '~. s_ , . ~x r-. 5 `~~ ~ : ~. ko,. ;~+ "q•~,I . _ 1T1s ~•t} ~~ 'F. ~_ ~~ G ~~~ ~ «ti. ~,. ~. 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