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HomeMy WebLinkAbout09A-GEOTECH REPORTArboricultural Assessment Helen Smith 1353 Thorndyke Road Port Ludlow WA Richard R Hefley— Consulting Arborist PO Box 177, 101 Reinier Road Nordland WA A P R 2 6 2021 Page 2 of 15 Arboricultural Assessment Client: Helen Smith 1353 Thorndyke Road Port Ludlow WA Author: Richard R Hefley Consulting Arborist Site Visit Date: 08/26/2020 Report Date : 09/13/2020 Amended: 04/06/2021 OBJECTIVES: Create a vegetation management plan for Lots #950100308 and 309, given these lots are designated as moderate landscape and erosion hazards. BACKGROUND I was contacted by Helen Smith of 1353 Thorndyke Road regarding concerns she had for acquiring and managing two lots adjacent to her residence. Richard R. Hefley — Consulting Arborist — 360-385-2921— rkheflev@olypen.com Page 3 of 15 CONTENTS: Page 04 ..... Executive Summary Page 05 ..... Observations — Aerial Photo, View Corridor Delineation Page 06 ..... Aerial Photo: Vegetation Zones of Slope Page 07 ..... Mid -Slope Zone: Douglas Firs Pages 08-09 ..... Upper Slope Zone: Blackberries, Sword Ferns, Salal Pages 10-11.... Lower Slope Zone: Bigleaf Maples Discussion Page 12 .... Waiver of Liability, Contact Information Pages 13-14 ..... Pruning Notes Richard R. Hefley Consulting Arborist — 360-385-2921— rkhefley@olypen.com Page 4 of 15 EXECUTIVE SUMMARY: I was contacted by Helen Smith of 1353 Thorndyke Road regarding concerns she had for acquiring and managing two lots adjacent to her residence. There are essentially three "Zones" associated with the slope of these two lots. The crown of the slope, the upper zone, consists of a groundcover of native salal and sword fern, a non-native low juniper, and Himalayan Blackberry (a noxious weed). The middle zone consists primarily of Douglas Fir and Western Hemlocks. The toe of the slope, the lowest zone, consists primarily of Bigleaf Maples and red Alder. Given that these lots are designated as moderate erosion and landslide zones, it is important to maintain healthy evergreen vegetation to mitigate the associated hazards. This vegetation maintenance should consist of pruning and the replacement of noxious weeds with appropriate vegetation, bearing in mind the importance of encouraging an evergreen covering of the ground using native low plants and trees. The current pruning and thinning necessity lies with the Douglas Fir and Western Hemlock trees that have grown to obscure the View Corridor associated with this property. Several suppressed and diseased trees may be removed without exposing any ground to erosion hazard. Remaining trees may be pruned using approved methods including "thinning, windowing, and crown raising." Details on pruning techniques are noted in the appendices. I attached aluminum tags and colored tape to trees. Orange tape designates trees that may be removed. Blue tape designates trees that may be pruned. The trees to be removed are numbered; 02, 04, 08, 10. Other scattered young Bigleaf Maples with trunks less than 6" in diameter located on the lower slope are not numbered but may be removed without any measurable environmental degradation to the area. The remaining conifers appear to be in good health and can sustain pruning of 25% of the canopy area with no measurable impact to their immediate environment. Removed foliage should be mulched and left in place for decomposition or removed from the slope entirely to mitigate the buildup of "fuel" for wildfire. Trunks of larger removed trees may be anchored across the slope by affixing them to remaining trees or tree stumps. In time the Bigleaf Maples and Red Alder located in the mid and lower slope may begin to obstruct the view corridor. These may be successfully controlled using "crown reduction" pruning techniques to retain the health and integrity of the tree. Smaller Maples and Alders measuring approximately 6" or less in diameter trunks may be removed. There is an abundance of the noxious weed, Himalayan Blackberry, primarily in the upper portion of the slopes. I recommend that these blackberry canes be removed and, at a minimum, be replaced with native evergreen groundcover and small shrubs that thrive in this area such as sword fern and salal. Other suitable additions to this slope may include groundcovers like mahonia and evergreen Richard R. Hefley — Consulting Arborist — 360-385-2921— rkheflev@olypen.com Page 5 of 15 huckleberry, or even Shore Pine, a native evergreen tree whose roots will bind the soils at a deeper level. Likewise, the lower portions of the lots below the canopies of the Bigleaf Maples would benefit from the addition of native evergreens to mitigate soil erosion and aid in the transpiration of stormwater in the cool and rainy seasons. Sword Fern and Evergreen Huckleberry are also excellent choices for this shady area. Suitable evergreen trees for this area are Western Red Cedar, though bearing in mind that these will eventually require pruning to keep the View Corridor open in a few decades. All work should be performed when soils are not waterlogged. Working on slopes when soils are saturated leads to soil damage and erosion if care is not exercised. All pruning will be done in accordance with ANSI A300 standards and adhering to AND Z133 Safety Standards, as well as Best Management Practices Revised 2008, Edward F Gilman and Sharon J Lilly. OBSERVATIONS: Richard R. Hefley — Consulting Arborist — 360-385-2921— rkheflev@alypen.com Page 6 of 15 The aerial photo above shows the Smith residence at 1353 Thorndyke Road. The red lines extending east roughly approximate the boundaries of two lots to acquire and manage the vegetation in a manner consistent with limiting potential erosion or landslide conditions. 1353 Thorndyke Road - Vegetation Areas �.I Write a description for your map The lots are divided into three basic vegetation types that correspond with the slope. The crown (top) of the slope is located immediately left of the Blue area and the toe (bottom) of the slope is located to the right of the yellow area (east). BLUE — This is the upper portion of the slope and most arid. It primarily consists of the native evergreen groundcovers salal and western sword fern, but also contains abundant amounts of Himalayan blackberry (a noxious weed) and scattered small trees and shrubs of a deciduous nature. RED — The middle portion of the lot is dominated by Douglas Fir trees, a conifer crucial to maintain to retain the integrity of the slope and mitigate potential erosion and landslides. Conifers, and indeed ALL evergreen trees and shrubs are critical to reduce the effects of stormwater erosion. Evergreen foliage deflects and scatters rain in the winter months when rain is (by far) most abundant and potentially damaging in this region. YELLOW — This portion is primarily associated with the lower, flatter portions of the lots where erosion and landslides are less likely to be a factor. The lowest portion is dominated by the native Bigleaf Maple (Acer macrophyllum) though a few trees are also scattered throughout the slope. There is a small number of red Alders (Alnus rubra) here as well. While their canopies aid somewhat in the mitigation of erosion, their greater benefit comes from their root systems that bind the soils. Richard R. Hefley — Consulting Arborist — 360-385-2921— rkheflev@olvQen.com Page 8 of 15 There are eleven Douglas Firs (Pseudotsuga menziesii) and Western Hemlocks (Tsuga heterophylla) located mid -slope on these two lots. Their continued health and stability is of primary importance to maintain the integrity of the soils around them. Most of these trees appear to be in good health and structurally sound. Tree #02 is in poor health and condition and should be removed. Tree #04 is in moderate health and suppressed by closely growing neighboring trees and should be removed. Tree #08 is suppressed and should be removed. Tree #10 is suppressed by closely growing larger neighboring trees and should be removed. Remaining conifers may be pruned using windowing, thinning, and crown raising techniques to regain lost views without compromising health and functions. The most important factor to bear in mind is that the canopy extends to cover the maximum square footage of the slope as possible. Consider them from the "bird's eye" point of view when pruning. The goal is to have foliage disrupt rain before it reaches the ground. The "rule of thumb" for maximum pruning of a healthy tree is 25% of the canopy though this amount may be adjusted for various factors not visible on the initial examination. I leave the final judgement to the tree professionals present at the job site. Richard R. Hefley — Consulting Arborist — 360-385-2921— rkhefley@olypen.com Page 9 of 15 Upper portion of Lots. Low vegetation includes non-native Juniper, the noxious weed Himalayan Blackberry, Western Sword Fern and Salal. The dense evergreen border of Salal/Fern/Juniper that marks the transition from lawn grass to slope at the crown of the slope should be maintained in place. This is the first line to capture and disperse stormwater from the impervious areas associated with the residence. Richard R. Hefley — Consulting Arborist — 360-385-2921— rkheflev@olvpen.com Page 10 of 15 This upper portion of the slope receives the largest amount of stormwater both from the sky and the impervious surfaces associated with the residence above it. It is important that this retain native evergreen vegetation, as well as mitigating the noxious Himalayan Blackberry that is now abundant here. These noxious weeds can be controlled by repeated pruning, best done in the late summer/early autumn months, as well as a careful application of concentrated herbicide to freshly cut canes. The herbicide will help kill the roots but will not disturb the soils. Areas covered by blackberry are likely to be barren when the weed is removed. These areas should be replanted with native evergreen plants in order to mitigate stormwater and improve soil stability. Plantings should be done in Autumn (October/November) when seasonal rains will adequately irrigate the seedlings. To limit soil disturbances on the slopes it is best that small seedlings be planted. The most promising natives growing here are the Sword Fern (Polystichum munitum) and Salal (Gaultheria shallon). This area may benefit from large native evergreens such as Evergreen Huckleberry (Vaccinium ovatum), Mahonia, and even Shore Pine (Pinus contorta). Though the pine may eventually require pruning to maintain views, they are easy to prune and maintain at a low height and serve the added function of binding the slope soils more deeply due to their root systems. Richard R. Hefley — Consulting Arborist — 360-385-2921— rkhefley@olyoeii.com Page 11 of 15 Bigleaf maples (Acer macrophyllum) located on the lower slopes of the These are primarily growing on the flattest areas and have very few groundcovers below their canopy. Stormwater management would benefit from the addition of native evergreens like Sword Fern and Evergreen Huckleberry. Richard R. Hefley — Consulting Arborist — 360-385-2921— rkhefley@oiypen.com Page 12 of 15 Note the presence of the ubiquitous Sword Fern below these maples. These remain the best and most effective groundcover in this area due to their wide range of adaptability (sun/shade/drought/damp) DISCUSSION: To achieve the balance of retaining the ecological functions of the vegetation with the maintenance of a view corridor will require periodic work sessions. The overall goal is to keep the ground covered with a living canopy of evergreen vegetation to prevent stormwater from exacerbating erosion, while reducing fuels on or near the ground level, maintaining the health of the vegetation while maintaining the view corridor. It is a juggling act but is easier than it sounds. The fist step is to remove unhealthy and suppressed conifers to allow for the more rapid growth and greater health of the remaining trees. Following this you may prune the conifers that are obstructing the View Corridor, chipping the debris into mulch for easy decomposition (preferable) or removing the debris entirely so as to not add dried fuel that will exacerbate fire dangers on a slope. Trunks or large limbs may be anchored across the face of the slope using remaining trees or tree stumps. I recommend the removal of the noxious weeds by cutting to the ground. If weather conditions permit, this would be the preferable time to apply herbicide to limit regrowth of the weed in the spring. October/November are the best months to replant exposed slope areas with evergreen native vegetation. Sword Fern is usually the most versatile and hardy plant. Salal, Mahonia, and Evergreen Huckleberry are also good choices to mix in. Shore Pine seedlings are also a good choice to include. The groundcover seedlings should be planted on a (roughly) 12" (inch) spacing, while the Shore Pines should be spaced approximately 12' (feet) apart. A tree protection tube is helpful for establishing young trees. Richard R. Hefley — Consulting Arborist — 360-385-2921— rkhefley@olyperi.com Page 13 of 15 WAIVER OF LIABILITY: Many factors affect a tree's health and stability that are not discernible in the course of a visual examination. My conclusions represent an opinion of a tree's health and stability at this particular point in time. This report does not guarantee the future safety of the trees or predict future events that may affect these trees. A second opinion by a qualified assessor is always recommended. The property owner is responsible for scheduling future examinations and/or recommended maintenance. The property owner is responsible for obtaining required permits from all concerned governing bodies from federal to state, county, city, and home owner associations. The property owner is responsible for obtaining and providing all applicable codes, covenants and restrictions (CC&Rs) that apply. The client shall hold the evaluator harmless for injuries or damages incurred if recommendations are not heeded or for acts of nature beyond reasonable expectations such as severe winds, excessive rain, heavy snow loads, ice, earthquakes etc. This report and all attachments, enclosures and references are confidential and intended for the use of the client referenced above. They may not be reproduced, used in any way or disseminated in any form without the consent of the client and Richard Hefley — Consulting Arborist. Richard R. Hefley Consulting Arborist 360-385-2921 rkhefieV,ffi)olypen_com PO Box 177 101 Reinier Road Nordland WA 98358 Richard R. Hefley — Consulting Arborist — 360-385-2921— rkheflev@olyUn.com Page 14 of 15 Notes on Pruning: Pruning should be done in conformation to ANSI A300 Standards. When pruning trees, I recommend the woody debris be ground into chips or broken down into the smallest pieces possible and distributed throughout the area beneath the tree canopy. This debris will break down and provide future nutrients for the remaining trees, as well as build up the soil layers and aid the mycchorizai organisms that live in the soil and are a critical part of water and nutrient uptake (yes, the soil is, literally, alive). Light pruning (10% or less of the live canopy) can be done any time of year. Heavy pruning is best left for winter months when trees are in their maximum state of dormancy. Pruning should never exceed 25% of a tree's canopy, though this amount can be modified depending on the tree's age, health and species. If pruning for safety, the season should be discounted and pruning take place as soon as practical. It is best to have all safety pruning completed before the end of October, which generally is the commencement of our wind -storm season. Another viable option is to leave the branch stubs in place to serve as habitat for beneficial organisms, from fungi to mammals. This technique (or lack thereof) is being more and more encouraged by tree care professionals as it replicated what would be done naturally. In a similar vein, wood chips and debris are encouraged to be allowed to remain beneath the tree to decompose and serve as a source of mulch and nutrients for the tree. Pruning for View There are essentially five methods for pruning trees for view; 1. Thinning 2. Windowing 3. Limbing Up/Crown Raising 4. Crown Reduction, or a combination of these. It is important to not remove too much foliage. The "rule of thumb" is to remove no more than 25% of the canopy at one time, but this should be adjusted to account for the species, the age, the health, and the time of year the pruning is done. Many say this amount may be removed yearly, but my opinion is that one should wait several years before conducting another "maximum" pruning (25%) to avoid stress on the tree and allow more foliage to take the place of what was lost. Light pruning (less than 10% of canopy) can be done yearly and regardless of the season. Richard R. Hefley — Consulting Arborist — 360-385-2921— rkhefley@olypen.com Page 15 of 15 Before Crown Crown Crown Cleaning Thinning Raising Crown Reduction 5. Living Habitat Tree. Another technique is a more severe alteration of the tree, the creation of a Habitat Tree, which entails removing as much as 80% of the tree (and most likely shortening the life span of the tree). This technique is replicating natural storm damage trees suffer which results in their losing the majority of their crowns while retaining enough foliage to survive and provide habitat for a large variety of birds, animals and fungi. The tree will also retain its critical functions of transpiration, rainfall interdiction and soil cohesion. Richard R. Hefley — Consulting Arborist — 360-385-2921— rkheflev@olyoen.com