Loading...
HomeMy WebLinkAbout24_Arborist-Report Arborist Report Skattum Plat 17018 & 17022 106th Ave SE Renton, WA December 13th, 2016 American Forest Management 12/13/2016 Table of Contents 1. Introduction .............................................................................................................. 1 2. Description ............................................................................................................... 1 3. Methodology ............................................................................................................ 1 4. Observations ........................................................................................................... 2 5. Discussion ............................................................................................................... 3 6. Tree Retention ......................................................................................................... 3 7. Tree Replacement .................................................................................................. .3 8. Tree Protection Measures…………………………………………………………………4 Appendix Site/Tree Photos – pages 7 - 12 Tree Summary Table – attached Tree Locator Map - attached Tree Plan Map – attached City of Renton Tree Protection Measures – page 6 Skattum Plat - Arborist Report Page 1 American Forest Management 12/13/2016 1. Introduction American Forest Management, Inc. was contacted by Keith Litchfield of Litchfield Engineering and was asked to compile an ‘Arborist Report’ for two parcels located within the City of Renton. The proposed subdivision encompasses the properties at 17018 & 17022 106th Ave SE. Our assignment is to prepare a written report on present tree conditions, which is to be filed with the preliminary permit application. This report encompasses all of the criteria set forth under City of Renton code section 4-4-130. The tree retention requirement is 30% of significant trees. Date of Field Examination: December 6th, 2016 2. Description 70 significant trees were identified and assessed on the property. According to City of Renton code, a significant tree is a tree with a caliper (trunk diameter measured 4-1/2’ above the ground) of at least 6” or an alder or cottonwood tree with a caliper of at least 8”. Trees planted within the most recent 10 years qualify as significant trees, regardless of the actual caliper. A numbered aluminum tag was placed on the lower trunks of the subject trees. These numbers were used for this assessment. Tree tag numbers correspond with the numbers on the Tree Summary Tables and copy of the attached site survey. There are eight neighboring trees with a drip lines that extend over the property line. 3. Methodology Each tree in this report was visited. Tree diameters were measured by tape. The tree heights were measured using a Spiegel Relaskop. Each tree was visually examined for defects and vigor. The tree assessment procedure involves the examination of many factors:  The crown of the tree is examined for current vigor. This is comprised of inspecting the crown (foliage, buds and branches) for color, density, form, and annual shoot growth, limb dieback and disease. The percentage of live crown is estimated for coniferous species only and scored appropriately.  The bole or main stem of the tree is inspected for decay, which includes cavities, wounds, fruiting bodies of decay (conks or mushrooms), seams, insects, bleeding, callus development, broken or dead tops, structural defects and unnatural leans. Structural defects include crooks, forks with V-shaped crotches, multiple attachments, and excessive sweep.  The root collar and roots are inspected for the presence of decay, insects and/or damage, as well as if they have been injured, undermined or exposed, or original grade has been altered. Based on these factors a determination of condition is made. The four condition categories are described below based on the species traits assessed: Excellent – free of structural defects, no disease or pest problems, no root issues, excellent structure/form with uniform crown or canopy, foliage of normal color and density, above average vigor, it will be wind firm if isolated, suitable for its location Good – free of significant structural defects, no disease concerns, minor pest issues, no significant root issues, good structure/form with uniform crown or canopy, foliage of normal color and density, average or normal vigor, will be wind firm if isolated or left as part of a grouping or grove of trees, suitable for its location Skattum Plat - Arborist Report Page 2 American Forest Management 12/13/2016 Fair – minor structural defects not expected to contribute to a failure in near future, no disease concerns, moderate pest issues, no significant root issues, asymmetric or unbalanced crown or canopy, average or normal vigor, foliage of normal color, moderate foliage density, will be wind firm if left as part of a grouping or grove of trees, cannot be isolated, suitable for its location Poor – major structural defects expected to fail in near future, disease or significant pest concerns, decline due to old age, significant root issues, asymmetric or unbalanced crown or canopy, sparse or abnormally small foliage, poor vigor, not suitable for its location A ‘viable’ tree is “A significant tree that a qualified professional has determined to be in good health, with a low risk of failure due to structural defects, is wind firm if isolated or remains as part of a grove, and is a species that is suitable for its location.” Trees considered ‘non-viable’ are trees that are in poor condition due to disease, age related decline, have significant decay issues and/or cumulative structural defects, which exacerbate failure potential. The attached tree map indicates the ‘condition’ of the subject trees found at the site. 4. Observations The subject trees are primarily native, mature conifers. Specific tree information for individual trees can be found on the attached tree table. The Douglas-fir trees on the property are generally healthy and mature, estimated at 60 – 70 years of age. Most were planted in rows or clusters. The row of Douglas-fir trees on the west property line, #150 - #156, are growing very closely together and should not be isolated. One incident of fungal disease was observed. A Phaeolus schweinitzii conk was found 1’ from the trunk of tree #132. The vigor of tree #132 is good and the infection is suspected to be incipient. Foliage color is good. All of the Douglas-fir trees on the site are viable. The western red cedar trees on the property are generally mature. Most of the western red cedar trees on the property are in groupings. Decay was observed in multiple trees. The decay is suspected to be brown cubical rot, but no fungal fruiting bodies were found. Some of the western red cedar trees were topped in the past. Co- dominant trunks with included bark were commonly observed and are the most concerning defect. The western red cedar trees on the property range in condition and all but one are viable. Tree #165 - #167 are black cottonwood trees on the west side of the property. Tree #165 and #166 are mature black cottonwoods growing closely together. Tree #165 has a DBH of 54” and a height of 167’. Tree #166 has a DBH of 45” and a height of 154’. Large limbs on both tree have failed but no other concerning defects were observed. Tree #167 is younger. The top of this tree broke off and there is decay in the trunk. All three trees are viable. Tree #149 is an English oak on the west property line. This tree has a forked trunk. The attachment between the two trunks is good. The crown is full and no other defects were observed. This tree is in good condition and is viable. Tree #125, #130 and #131 are European larch trees on the west side of the property. Tree #130 and #131 have poor trunk taper. All three trees are viable. Neighboring Trees Tree #201 - #206 are mature big leaf maple trees north and east of the property lines. Big leaf maple trees often have large lateral branches. Co-dominant trunks with included bark were the most common defects observed. All six trees are in fair to good condition and are viable. Tree #207 is a mature Douglas-fir south of the property line. This tree has no concerning defects, is in good condition and is viable. Skattum Plat - Arborist Report Page 3 American Forest Management 12/13/2016 5. Discussion The extent of drip-lines (farthest reaching branches) for the subject trees can be found on the tree summary tables at the back of this report. These have also been delineated on a copy of the site survey for viable/healthy trees proposed for retention. The information plotted on the attached survey plan may need to be transferred to a final tree retention/protection plan to meet City submittal requirements. The trees that are to be removed shall be shown “X’d” out on the final plan. The Limits of Disturbance (LOD) measurements can also be found on the tree summary table. This is the recommended distance of the closest impact (soil excavation) to the trunk face. These should be referenced when determining tree retention feasibility. The LOD measurements are based on species, age, condition, drip- line, prior improvements, proposed impacts and the anticipated cumulative impacts to the entire root zone. Tree Protection fencing shall be located beyond the drip-line edge of retained trees, and only moved back to the LOD when work is authorized. Trees on the property growing closely together are recommended for retention as groupings. One example is the row of Douglas-fir trees, #150 - #156 are growing in a row with only a few feet between each trunk. When trees are growing closely together, they often develop small trunk taper and live crown ratios. As long as the trees are retained as groupings and not isolated, the risk of failure is lessened. A Phaeolus schweinitzii conk was found 1’ from the trunk of tree #132. The vigor of tree #132 is good and the infection is suspected to be incipient. All conifers are susceptible to Phaeolus schweinitzii and it is likely present in multiple trees on the property. Trees in advanced stages of the disease often have thin crowns and/or branch dieback, and swollen lower trunks. No trees with advanced or significant internal decay were identified. The western red cedar trees on the property are mature and some concerning defects were observed. Brown cubical rot is suspected to be in multiple western red cedar trees on the property. The development of internal decay columns within mature cedar is common. As long as trees are vigorous and actively growing, the risk of failure remains low. Western red cedars are good at compartmentalizing decay radially and the presence of rot is not necessarily an indication that the tree is declining. The largest concern with the western red cedar trees on the site is co-dominant stems with included bark. Tree #115 is a western red cedar with co-dominant stems that have split apart. Failure of this tree is extremely likely. Tree #115 is a high risk tree and should be removed before work commences on the site. The tree density on the site is currently low and mainly concentrated in the southwest region of the property. Most of the trees are in the center and west side of the property. Sidewalk improvements, water utilites and the construction of new homes will prevent retention of the majority of the existing trees. The site will fall 8% short of meeting the required 30% significant tree retention requirement. New trees will be planted to mitigate for the tree removal and to enhance the landscape. There are no concerns with neighboring trees. The tree protection measures below will serve to protect these trees. 6. Tree Retention A total of 70 significant trees were identified on the subject property. One of the significant trees is in poor condition. This tree was not included in the tree calculation. Landmark trees and tree groves were prioritized when selecting trees for retention, per the City of Renton tree code 4-4-130. Tree Calculation based on 69, healthy, viable, significant trees Viable Trees proposed for removal – 54 (78%) Viable Trees proposed for retention – 15 (22%) Skattum Plat - Arborist Report Page 4 American Forest Management 12/13/2016 7. Tree Replacement Replacements trees may be required. Consult your city planner for tree replacement requirements. All replacement trees are to be planted on site. For planting and maintenance specifications, refer to Section 4-4- 130 of the Renton Tree Ordinances. 8. Tree Protection Measures The following guidelines are recommended to ensure that the designated space set aside for the preserved trees are protected and construction impacts are kept to a minimum. Refer to the City of Renton Code 4-4-130- 9. Protection Measures During Construction for more information.  Tree protection barriers shall be initially erected at 5’ outside of the drip-line prior to moving any heavy equipment on site.  Tree protection fencing shall only be moved where necessary to install improvements, but only as close as the Limits of Disturbance, as indicated on the attached plan.  Excavation limits should be laid out in paint on the ground to avoid over excavating.  Excavations within the drip-lines shall be monitored by a qualified tree professional so necessary precautions can be taken to decrease impacts to tree parts. A qualified tree professional shall monitor excavations when work is required and allowed up to the “Limits of Disturbance”.  To establish sub grade for foundations, curbs and pavement sections near the trees, soil should be removed parallel to the roots and not at 90 degree angles to avoid breaking and tearing roots that lead back to the trunk within the drip-line. Any roots damaged during these excavations should be exposed to sound tissue and cut cleanly with a saw. Cutting tools should be sterilized with alcohol.  Areas excavated within the drip-line of retained trees should be thoroughly irrigated weekly during dry periods.  Preparations for final landscaping shall be accomplished by hand within the drip-lines of retained trees. Plantings within the drip lines shall be limited. Large equipment shall be kept outside of the tree protection zones. Tree Type Removal Retained Total Landmark # 11 0 11 Landmark % 100% 0% 100% Significant # 43 15 58 Significant % 74% 26% 100% Total # 54 15 69 Total % 78% 22% 100% Skattum Plat - Arborist Report Page 5 American Forest Management 12/13/2016 There is no warranty suggested for any of the trees subject to this report. Weather, latent tree conditions, and future man-caused activities could cause physiologic changes and deteriorating tree condition. Over time, deteriorating tree conditions may appear and there may be conditions, which are not now visible which, could cause tree failure. This report or the verbal comments made at the site in no way warrant the structural stability or long term condition of any tree, but represent my opinion based on the observations made. Nearly all trees in any condition standing within reach of improvements or human use areas represent hazards that could lead to damage or injury. Please call if you have any questions or I can be of further assistance. Sincerely, Kelly Wilkinson kelly.wilkinson@afmforest.com ISA Certified Arborist #PN-7673A ISA Tree Risk Assessment Qualified Skattum Plat - Arborist Report Page 6 American Forest Management 12/13/2016 City of Renton Code 4-4-130- 9. Protection Measures During Construction a. Construction Storage Prohibited: The applicant may not fill, excavate, stack or store any equipment, dispose of any materials, supplies or fluids, operate any equipment, install impervious surfaces, or compact the earth in any way within the area defined by the drip line of any tree to be retained. b. Fenced Protection Area Required: Prior to development activities, the applicant shall erect and maintain six-foot (6') high chain link temporary construction fencing around the drip lines of all retained trees or at a distance surrounding the tree equal to one and one-quarter feet (1.25') for every one inch (1") of trunk caliper, whichever is greater, or along the perimeter of a tree protection tract. Placards shall be placed on fencing every fifty feet (50') indicating the words, “NO TRESPASSING – Protected Trees,” or on each side of the fencing if less than fifty feet (50'). Site access to individually protected trees or groups of trees shall be fenced and signed. Individual trees shall be fenced on four (4) sides. In addition, the applicant shall provide supervision whenever equipment or trucks are moving near trees. c. Protection from Grade Changes: If the grade level adjoining to a tree to be retained is to be raised, the applicant shall construct a dry rock wall or rock well around the tree. The diameter of this wall or well must be equal to the tree’s drip line. d. Impervious Surfaces Prohibited within the Drip Line: The applicant may not install impervious surface material within the area defined by the drip line of any tree to be retained. e. Restrictions on Grading within the Drip Lines of Retained Trees: The grade level around any tree to be retained may not be lowered within the greater of the following areas: (i) the area defined by the drip line of the tree, or (ii) an area around the tree equal to one and one-half feet (1-1/2') in diameter for each one inch (1") of tree caliper. A larger tree protection zone based on tree size, species, soil, or other conditions may be required. (Ord. 5676, 12-3-2012) f. Mulch Layer Required: All areas within the required fencing shall be covered completely and evenly with a minimum of three inches (3") of bark mulch prior to installation of the protective fencing. Exceptions may be approved if the mulch will adversely affect protected ground cover plants. (Ord. 5676, 12-3-2012) g. Monitoring Required during Construction: The applicant shall retain a certified arborist or licensed landscape architect to ensure trees are protected from development activities and/or to prune branches and roots, fertilize, and water as appropriate for any trees and ground cover that are to be retained. h. Alternative Protection: Alternative safeguards may be used if determined to provide equal or greater tree protection. (Ord. 5676, 12-3-2012) Skattum Plat - Arborist Report Page 7 American Forest Management 12/13/2016 Photos Northeast corner of the subject property Cluster of western red cedar trees (#106 - #108) Skattum Plat - Arborist Report Page 8 American Forest Management 12/13/2016 Tree #103 and #102 – big leaf maple and Douglas-fir trees Tree #114 – western red cedar with a self-corrected lean and column of trunk decay Skattum Plat - Arborist Report Page 9 American Forest Management 12/13/2016 Tree #113 – western red cedar with column of decay Grouping of western red cedar trees (#109 - #114) Skattum Plat - Arborist Report Page 10 American Forest Management 12/13/2016 Tree #115 – western red cedar with forked trunk and severe decay West side of subject property Skattum Plat - Arborist Report Page 11 American Forest Management 12/13/2016 Tree #132 – Douglas-fir tree with Phaeolus schweinitzii conk Tree #133 – European white birch with a large burl Skattum Plat - Arborist Report Page 12 American Forest Management 12/13/2016 East side of subject property, tree #169 in the center Tree #167 – black cottonwood with poor form Tree Summary Table American Forest Management, Inc. For:Skattum Plat Date:12/7/2016 City of Renton Inspector:Wilkinson Tree/DBH Height Tag #Species (inches)(feet)Condition Viability Comments Proposal N S E W 101 Douglas-fir 22 96 13 / 10 17 / 10 good viable retain 102 Douglas-fir 28 103 14 / 12 11 / 12 16 / 12 8 / 12 good viable Slight lean E retain 103 big leaf maple 29 85 12 / 12 21 / 12 19 / 12 18 / 12 good viable retain 104 Douglas-fir 12 42 9 / 6 14 / 6 17 / 6 fair viable retain 105 western red cedar 20 81 13 10 17 4 good viable remove 106 western red cedar 28 52 4 17 16 6 fair viable Topped remove 107 western red cedar 24 78 10 8 4 6 good viable remove 108 western red cedar 34 72 18 21 11 23 good viable landmark tree remove 109 western red cedar 37 45 10 17 15 10 good viable landmark tree remove 110 western red cedar 32 103 17 9 12 11 fair viable Top broke off, landmark tree remove 111 western red cedar 20 76 4 13 6 6 good viable remove 112 western red cedar 28, 24 (37)96 17 19 8 9 fair viable Forks at 2', landmark tree remove 113 western red cedar 25 77 18 6 5 17 fair viable Decay remove 114 western red cedar 32 68 2 17 7 14 fair viable decay, forked top, slight lean S, landmark tree remove 115 western red cedar 24 46 poor non-viable Trunk splitting, hazardous - non-significant remove 116 western red cedar 28 79 16 10 20 fair viable Connected at base to tree 115 remove 117 western red cedar 33 89 17 / 16 17 / 16 14 / 16 16 / 16 good viable Trunk forks at ~30', some included bark, landmark tree remove 118 Douglas-fir 27 109 8 / 13 10 / 13 12 / 13 9 / 13 good viable flat trunk on north side retain 119 Douglas-fir 26 120 4 / 12 15 / 12 9 / 12 4 / 12 good viable retain 120 Douglas-fir 21 91 12 / 10 9 / 10 16 / 10 good viable retain 121 Douglas-fir 16 81 5 / 8 9 / 8 12 / 8 6 / 8 fair viable retain 122 Douglas-fir 31 118 9 18 6 16 good viable landmark tree remove 123 Douglas-fir 28 111 13 8 9 11 good viable some old lower trunk bleeding remove 124 Douglas-fir 29 118 7 / 12 11 / 12 11 / 12 good viable retain 125 European larch 10 30 10 9 2 9 fair viable remove 126 Douglas-fir 38 110 20 25 24 18 good viable landmark tree remove 127 western red cedar 35 78 19 18 21 good viable landmark tree, in 106th Ave SE right-of-way remove 128 quaking aspen 11 55 9 6 5 11 good viable remove 129 quaking aspen 7 27 0 11 8 2 fair viable remove 130 European larch 14 76 10 6 7 9 fair viable poor trunk taper remove 131 European larch 15 74 6 8 6 11 fair viable poor trunk taper remove Drip-Line/Limits of Disturbance (feet) Tree Summary Table American Forest Management, Inc. For:Skattum Plat Date:12/7/2016 City of Renton Inspector:Wilkinson Tree/DBH Height Tag #Species (inches)(feet)Condition Viability Comments Proposal N S E W Drip-Line/Limits of Disturbance (feet) 132 Douglas-fir 20 74 10 13 6 15 fair viable Phaeolus schweinitzii conk found 1' from trunk on east side remove 133 European white birch 16 64 13 12 7 16 fair viable Burl on trunk remove 134 grand fir 28 77 12 16 14 15 good viable Forked top remove 135 western red cedar 26 84 15 12 19 12 fair viable Forked trunk, minor included bark remove 136 Douglas-fir 13 81 7 10 9 5 good viable remove 137 Douglas-fir 25 115 11 10 8 12 good viable remove 138 Douglas-fir 16 95 10 7 6 12 good viable remove 139 Douglas-fir 24 111 11 17 12 23 good viable remove 140 Douglas-fir 16 100 3 7 6 10 good viable remove 141 Douglas-fir 17 98 11 10 6 12 good viable remove 142 Douglas-fir 22 109 11 14 8 10 good viable remove 143 Douglas-fir 28 110 8 / 13 18 / 13 6 / 13 14 / 13 good viable remove 144 Douglas-fir 33 101 15 / 15 16 / 15 18 / 15 8 / 15 good viable landmark tree remove 145 western red cedar 22 83 6 / 12 12 / 12 16 / 12 5 / 12 good viable in grouping with tree #146 remove 146 western red cedar 27 85 8 / 14 11 / 14 9 / 14 11 / 14 good viable in grouping with tree #145 remove 147 Douglas-fir 29 118 15 8 11 13 good viable remove 148 Douglas-fir 19 100 7 7 9 14 good viable remove 149 English oak 25 91 4 19 11 17 good viable Forked trunk remove 150 Douglas-fir 17 45 13 11 17 good viable remove 151 Douglas-fir 20 95 10 11 good viable Slight lean N remove 152 Douglas-fir 19 91 16 15 good viable remove 153 Douglas-fir 11 63 11 8 good viable remove 154 Douglas-fir 18 85 12 14 good viable remove 155 Douglas-fir 19 83 6 14 good viable remove 156 Douglas-fir 12 52 8 7 7 good viable remove 157 western red cedar 23 38 15 12 11 good viable remove 158 western red cedar 13 23 10 9 9 good viable remove 159 western red cedar 18 39 14 / 15 7 / 15 12 / 15 fair viable Topped retain 160 western red cedar 14 45 13 / 12 9 / 12 7 / 12 fair viable Topped retain 161 western red cedar 19 55 12 / 10 9 / 10 10 / 10 good viable retain 162 western red cedar 23 61 12 / 16 10 / 16 6 / 16 good viable retain 163 Willow 6, 5, 4 (9)39 14 / 6 13 / 6 9 / 6 fair viable retain 164 Douglas-fir 12 51 14 / 6 15 / 6 good viable retain Tree Summary Table American Forest Management, Inc. For:Skattum Plat Date:12/7/2016 City of Renton Inspector:Wilkinson Tree/DBH Height Tag #Species (inches)(feet)Condition Viability Comments Proposal N S E W Drip-Line/Limits of Disturbance (feet) 165 black cottonwood 54 167 18 15 19 fair viable landmark tree remove 166 black cottonwood 45 154 18 17 11 fair viable Large limbs have failed, landmark tree remove 167 black cottonwood 12, 13 (17)55 17 19 16 17 fair viable decay, top broke off remove 168 western red cedar 23 54 16 13 14 14 good viable remove 169 Douglas-fir 23 94 10 17 15 15 good viable remove 170 western red cedar 25 85 8 9 11 11 good viable remove 201 big leaf maple 8, 7 (11)54 6 / 0 good viable Leans W, 10' east of property line protect 202 big leaf maple 16 71 6 / 2 fair viable protect 203 big leaf maple 18, 13, 15 (27)78 9 / 5 fair viable protect 204 big leaf maple 16, 18, 13 (27)70 12 / 14 fair viable 5' from property line protect 205 big leaf maple 29, 32 (43)111 5 / 14 16 / 14 19 / 14 good viable Trunk forks at base, good attachment, landmark tree protect 206 big leaf maple 28 73 18 / 12 good viable protect 207 Douglas-fir 28 94 10 / 2 good viable 8' S of property line protect 208 western red cedar 29, 16 (33)49 8 / 5 good viable 10' S of property line, landmark tree protect Drip-Line and Limits of Disturbance measurements from face of trunk Trees on neighboring properties - Drip-line and Limits of Disturbance measurements from property lines Calculated DBH: the DBH is parenthesis is the square root of the sum of the dbh for each individual stem squared (example with 3 stems: dbh = square root [(stem1)2 +(stem2)2 +(stem3)2]. Neighboring Trees