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Degan comment 2.pdfClugston, Michael From: Marilyn Degan [t.mdegan@gmail.com] Sent: Wednesday, February 13, 2013 9:49 PM To: Clugston, Michael Attachments: T.Russeff Ltr.pdf; IMG_2741.JPG Dear Mr Clugton, Regarding the project at 15500 75th pl w I previously sent the City a letter regarding concerns including; a property line issue, street drainage for our properties, and the need for a soldier wall on the west side bluff over the tracks. The enclosed letter from an arborist discusses the importance of trees on the property in retaining soils. The picture enclosed shows a slough on the south end of our property which recently occured. This is into the ravine which was the easment for 156th st SW which the City vacated to us previously. As the soils on the two properties are essentially the same I believe, the topsoil overlying a clay srtata which allows slides when wet or essentially liqufies and slides with vibration, (ie. train) which I have actually witnessed myself on my property prior to the soldierwall. .I think these enclosures re -enforce the need for a soldier wall to retain soils, as we have done, and as you required for development of the property to our south (Fong).since I would certainly expect a significant number of the trees will be removed during the development of the property. Respectfully, Thomas J Degan Terry Russeff 10802 29"' Dr. SE Everett, WA 98208 02/12/13 Thomas Degan RE: This letter is in reference to planned developments of property located at 15500 75a` Place West, Edmonds, Washington. Dear Dr. Degan; As a point of consideration and introduction, with increasing slide activity recently between Edmonds and Mulilteo, the impact of bluff stability and the interruptions to rail traffic may well set off a series of litigations against property owners, municipalities, construction companies, and more. The importance of bluff stability cannot be overlooked from standpoints of public safety, ecological aspects, and financial investments or losses. In the past I have witnessed or heard of investors violating ecological ordinances knowing they would have to pay the fines involved. The fine was calculated and balanced against the value of profit accrued through the violation and the whole process was just seen as a part of doing business. In an effort to gain control over this, the local municipalities have developed more thoughtful ecological standards through their planning and development departments. In recent years I have changed professions and am no longer active within either the International Society of Arboriculture or the National Arborist Association. However, in the past, because of projects I have done, planning, and reports, I had been asked to provide input to the City of Mukilteo as they developed their tree ordinances. With that said, I will speak of tree physiology, vegetation, and its importance as it blends with local geology and erosion control. At this time I am not certified, nor have I done a detailed site survey and report. The first thing to consider is the geological makeup of soil in the Puget Sound region. To simplify this, we are looking at glacial till covered with sediments, then a layer of topsoil. Add a tree to this, consider its physiology, and what goes on below the surface becomes more interesting. On the surface of the tree roots there are tiny lenticels. Their purpose is to provide the roots with oxygen that is trapped within the air pockets of the soil. Without retrieving this oxygen from the soil, respiration in the roots will not occur as oxygen is required for the digestion of the food that is produced in other parts of the tree. Ideal soil conditions for a tree are 50% air space and 50% particulate matter. Small anchor roots may grow into the glacial till, but many of these die off as the oxygen required for respiration is insufficient. And many times the ground water level is simply too high as the glacial till will not allow the water to penetrate this compacted layer. For these reasons, even trees that genetically develop taproots will pattern their root systems with most of their roots in the top two to three feet of soil and of these, 90% in the top six to eight inches. Exceptions to this do occur, but only when soil conditions permit. With the foliage area equal to the root mass, it is not uncommon to find roots out away from the tree anywhere from two to three times the height of the tree. These roots are valuable, not just for providing a structural maze to hold the soil, but also to transpire ground water out of the ground through the tree. A single tree can transpire hundreds of thousands of tons of water out of the ground. In transpiration, as temperature increases, stoma open up on the bottom side of the leaves and water is brought up from the roots and through the tree to be evaporated to cool the tree. As we remove these trees we not only lose the stability of the soil, but we increase our ground water content. And once the soil becomes saturated it loses a substantial amount of its strength. At this point and case the intermittent loading caused by the vibration of a passing train could cause liquefaction and gravity will do the rest. Now above the surface we have other considerations. To simplify concepts, only a few salient points will be necessary. Ideally we need three levels of protection. The upper, canopy level, will act as the first buffer to slow down the wind and rain. Mid-level, we have the understory which acts as a second level buffer, also absorbing the energy from the wind and rain. Both of these layers assist in protecting the last layer. Ground cover is thus the final layer which impedes surface run-off. When you think about this it is easy to see why guidelines suggest a mixture of native vegetation. So in conclusion, when all of the aspects are thought out, it is easy to see the significant roles of how a combination of engineered retaining walls and a mixture flora aid in erosion control. The vast root mass of the trees play an important role in both soil stabilization and ground water removal, while a variety of native plants protect the surface. Sincerely, Terry Russeff References: "Vegetation Management: A Guide For Puget Sound Bluff Property Owners" Washington State Department of Ecology Publication 93-31 "The Landscape Below Ground" Neely & Watson "Trees and Development: A Technical Guide to Preservation of Trees During Land Development' by Mathney and Clark "A Photographic Guide to the Evaluation of Hazard Trees in Urban Areas" by Mathney and Clark "Arboriculture: Integrated Management of Landscape Trees, Shrubs, and Vines" by Harris, Clark, and Matheny "Design in Nature: Learning from Trees" by Mattheck "The Body Language of Trees: A Handbook for Failure Analysis" by Mattheck and Breloer "Arboriculture and the Law" by Merullo and Valentine Personal notes from Pacific Northwest Chapter ISA Conference: `Bluff Management and Erosion Control"