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HomeMy WebLinkAbout08-28-2023 TC Agenda Packet Tree Committee AGENDA Monday, August 28, 2023, 5:30 p.m. Council Hearing Room, 990 Palm Street, San Luis Obispo The Tree Committee holds in-person meetings. Zoom participation will not be supported at this time. INSTRUCTIONS FOR PUBLIC COMMENT: Public Comment prior to the meeting (must be received 3 hours in advance of the meeting): Mail - Delivered by the U.S. Postal Service. Address letters to the City Clerk's Office at 990 Palm Street, San Luis Obispo, California, 93401. Email - Submit Public Comments via email to advisorybodies@slocity.org. In the body of your email, please include the date of the meeting and the item number (if applicable). Emails will not be read aloud during the meeting. Voicemail - Call (805) 781-7164 and leave a voicemail. Please state and spell your name, the agenda item number you are calling about, and leave your comment. Verbal comments must be limited to 3 minutes. Voicemails will not be played during the meeting. *All correspondence will be archived and distributed to members, however, submissions received after the deadline ma not be processed until the following day. Public Comment during the meeting: Meetings are held in-person. To provide public comment during the meeting, you must be present at the meeting location. Electronic Visual Aid Presentation. To conform with the City's Network Access and Use Policy, Chapter 1.3.8 of the Council Policies & Procedures Manual, members of the public who desire to utilize electronic visual aids to supplement their oral presentation are encouraged to provide display-ready material to the City Clerk by 12:00 p.m. on the day of the meeting. Contact the City Clerk's Office at cityclerk@slocity.org or (805) 781-7114. Pages 1.CALL TO ORDER Chair Elizabeth Lucas will call the Regular Meeting of the Tree Committee to order. 2.PUBLIC COMMENT FOR ITEMS NOT ON THE AGENDA The public is encouraged to submit comments on any subject within the jurisdiction of the Tree Committee that does not appear on this agenda. Although the Committee will not take action on items presented during the Public Comment Period, the Chair may direct staff to place an item on a future agenda for discussion. 3.CONSENT Matters appearing on the Consent Calendar are expected to be non- controversial and will be acted upon at one time. A member of the public may request the Tree Committee to pull an item for discussion. The public may comment on any and all items on the Consent Agenda within the three-minute time limit. 3.a CONSIDERATION OF MINUTES - JUNE 26, 2023 TREE COMMITTEE MINUTES 5 Recommendation: To approve the Tree Committee Minutes of June 26, 2023. 4.TREE REMOVAL APPLICATION 4.a 1815 MONTEREY STREET TREE REMOVAL APPLICATION 9 Recommendation: Review a Tree Removal Application to remove one (1) Incense Cedar (Calocedrus decurrens) tree at 1815 Monterey Street and provide a recommendation to the Community Development Director. 4.b 1414 SANTA ROSA STREET TREE REMOVAL APPLICATION 21 Recommendation: Review a Tree Removal Application to remove one (1) Black Wood Acacia (Acacia melanoxylon) tree at 1414 Santa Rosa Street and provide a recommendation to the Community Development Director. 5.COMMENT AND DISCUSSION 5.a MITCHELL PARK HERITAGE ASH TREE LEVEL 3 RISK ASSESSMENT 31 Receive an informational update from staff and review the Level 3 Risk Assessment Report for a Heritage Ash tree located in Mitchell Park, 1400 Osos Street. 5.b ARBORIST REPORT Receive a brief update from Acting City Arborist Anthony Whipple. 6.ADJOURNMENT The next Regular Meeting of the Tree Committee meeting is scheduled for September 25, 2023 at 5:30 p.m. in the Council Hearing Room at City Hall, 990 Palm Street, San Luis Obispo. LISTENING ASSISTIVE DEVICES are available -- see the Clerk The City of San Luis Obispo wishes to make all of its public meetings accessible to the public. Upon request, this agenda will be made available in appropriate alternative formats to persons with disabilities. Any person with a disability who requires a modification or accommodation in order to participate in a meeting should direct such request to the City Clerk’s Office at (805) 781-7114 at least 48 hours before the meeting, if possible. Telecommunications Device for the Deaf (805) 781-7410. Agenda related writings or documents provided to the Tree Committee are available for public inspection on the City’s website: https://www.slocity.org/government/mayor-and-city-council/agendas-and- minutes. Meeting video recordings can be found on the City’s website: http://opengov.slocity.org/WebLink/Browse.aspx?id=61087&dbid=0&repo=CityCl erk Page 4 of 59 1 Tree Committee Minutes June 26, 2023, 5:30 p.m. Council Hearing Room, 990 Palm Street, San Luis Obispo Tree Committee Members Present: Member Alan Bate, Member Henry Bonifas, Vice Chair Ben Parker, and Chair Elizabeth Lucas (one vacant seat) Tree Committee Members Absent: Members Daniel Canella and Emily Rosten City Staff Present: Acting City Arborist Anthony Whipple and Deputy City Clerk Kevin Christian _____________________________________________________________________ 1. CALL TO ORDER A Regular Meeting of the San Luis Obispo Tree Committee was called to order on June 26, 2023, at 5:30 p.m. in the Council Hearing Room at City Hall, 990 Palm Street, San Luis Obispo, by Chair Lucas. 2. PUBLIC COMMENT FOR ITEMS NOT ON THE AGENDA Public Comment: Dr. Joseph Morris John Ashbaugh --End of Public Comment-- 3. CONSENT 3.a CONSIDERATION OF MINUTES - APRIL 24, 2023, TREE COMMITTEE MINUTES Motion By Member Bate Second By Vice Chair Parker Approve the Tree Committee Minutes of April 24, 2023. Ayes (4): Members Bate and Bonifas, Vice Chair Parker, and Chair Lucas Absent (2): Member Canella and Member Rosten CARRIED (4 to 0) Page 5 of 59 2 4. TREE REMOVAL APPLICATION 4.a 1150 LAUREL LANE TREE REMOVAL APPLICATION City Arborist Anthony Whipple presented the staff report and responded to Commission inquiries. Applicant and owner representatives Jim Burrows and Michaela Denny provided background on the proposed building project and responded to questions raised. Chair Lucas opened the Public Hearing Public Comments: None --End of Public Comment-- Chair Lucas closed the Public Hearing Motion By Chair Lucas Second By Member Bate Recommend to the Community Development Director partial approval of Tree Removal Application SR#13794,1150 Laurel Lane , with the following modifications:  A tree protection plan shall be created for any retained trees throughout the overall construction project area; and  The larger trees, identified on the plans by numbers 5, 10, and 15 shall be retained; and  The remaining trees identified to be removed shall be replaced in the project site on a 2:1 basis with minimum 24 -inch box specimens, utilizing larger species native trees. Ayes (4): Members Bate, Bonifas, Vice Chair Parker, and Chair Lucas Absent (2): Members Canella and Rosten CARRIED (4 to 0) Page 6 of 59 3 4.b 1460 MADONNA ROAD TREE REMOVAL APPLICATION City Arborist Anthony Whipple presented the staff report and responded to Commission inquiries. He also noted that the Tree Committee’s purview is to make recommendations to the Community Development Director; they are not the final decision-maker as was noted on the agenda. Applicant representative, Michelle Glass, provided a brief overview of the project and responded to questions raised. Chair Lucas opened the Public Hearing Public Comments: None --End of Public Comment-- Chair Lucas closed the Public Hearing Motion By Member Bate Second By Vice Chair Parker Recommend to the Community Development Director denial of Tree Removal Application SR#13821; to remove one (1) Sweetgum (Liquidambar styraciflua) tree located at 1460 Madonna Road; with direction given to the applicant to further explore alternate solutions to tree removal for the underlying irrigation issue. Ayes (4): Members Bate, Bonifas, Vice Chair Parker, and Chair Lucas Absent (2): Members Canella and Rosten CARRIED (4 to 0) 5. COMMENT AND DISCUSSION 5.a ARBORIST REPORT Acting City Arborist Anthony Whipple provided an update of upcoming projects and activities in the Tree Division. 6. ADJOURNMENT The meeting was adjourned at 6:42 p.m. The next Regular Meeting of the Tree Committee is scheduled for July 24, 2023 at 5:30 p.m. in the Council Hearing Room at City Hall, 990 Palm Street, San Luis Obispo. _______________________ APPROVED BY TREE COMMITTEE: XX/XX/2023 Page 7 of 59 Page 8 of 59 DATE: August 16, 2023 TO: Tree Committee Members FROM: Anthony Whipple, City Arborist/Urban Forest Supervisor (805) 781-7021 awhipple@slocity.org SUBJECT: Tree Removal Application SR# 14008 COMMITTEE PURVIEW The Tree Committee’s role is to review the Tree Removal Application and provide a recommendation to the Community Development Director. On August 8, 2023, I posted one Incense Cedar tree at 1815 Monterey Street in response to Tree Removal Application SR#14008. The removal application was submitted based on: San Luis Municipal Code 12.24.090.E.1. E. Criteria and Process for Non-Construction Related Tree Removal Application Determinations Related to Tree Health or Hazard Mitigation or Property Owner Convenience (Refer to Subsection G of This Section for Criteria for Construction Tree Removal Determinations). ATTACHMENTS A - Tree Inspection Report B - Proof of Posting C - Tree Removal Application TREE COMMITTEE AGENDA REPORT Meeting Date: 8/28/2023 Item Number: 4a Time Estimate: 30 minutes Page 9 of 59 Page 10 of 59 Tree Removal Inspection Report TO: Vicki Carrol FROM: Anthony Whipple, City Arborist/Urban Forest Supervisor SUBJECT: Removal Application SR#14008 On August 8,2023, I Posted a Public Notice for a Tree Committee hearing for one Incense Cedar, (Calocedrus decurrens) tree(s) located at 1815 Monterey Street in response to tree removal application SR#14008. The removal of the mentioned application was submitted based on: San Luis Obispo Municipal Code 12.24.090 E.1 The Subject tree(s) is one Heritage Incense Cedar, (Calocedrus decurrens) (tree)s. The tree is located on property located in the Commercial zone; therefore, the Tree Committee shall review and make a recommendation on the tree removal application to the Community Development Director as authorized by the City of San Luis Obispo Municipal Code. “Heritage tree” means any tree existing within the city limits, which has been so designated by resolution of the city council. Heritage trees shall be trees with notable historic interest or trees of an unusual species or size. Thank you, Anthony Whipple, City Arborist/Urban Forest Supervisor (805) 781-7021 awhipple@slocity.org Public Works - Urban Forestry 25 Prado Road, San Luis Obispo, CA 93401-3218 805.781.7220 slocity.org Page 11 of 59 Page 12 of 59 Page 13 of 59 Page 14 of 59 Page 15 of 59 XPage 16 of 59 Page 17 of 59 Page 18 of 59 Page 19 of 59 Page 20 of 59 TREE COMMITTEE AGENDA REPORT DATE: August 16, 2023 TO: Tree Committee Members FROM: Anthony Whipple, Acting City Arborist/Urban Forest Supervisor (805) 781-7021 awhipple@slocity.org SUBJECT: Tree Removal Application SR# 14072 COMMITTEE PURVIEW The Tree Committee’s role is to review the Tree Removal Application and provide a recommendation to the Community Development Director. On August 14, 2023, I posted one (1) Black wood Acacia tree at 1414 Santa Rosa Street in response to Tree Removal Application SR#14072. The removal of the mentioned application was submitted based on: San Luis Municipal Code 12.24.090.E.3. E. 3. Tree removal requests based on property owner convenience shall be subject to tree committee review in accordance with the process set forth in subsection (F)(2) of this section, the relevant additional application requirements set forth in subsection (D)(2) of this section, and the criteria set forth in subsection G of this section ATTACHMENTS A - Tree Inspection Report B - Proof of Posting C - Tree Removal Application Meeting Date: 8/28/2023 Item Number: 4b Time Estimate: 15 minutes Page 21 of 59 Page 22 of 59 Tree Removal Inspection Report TO: Francisco Barroso FROM: Anthony Whipple, City Arborist/Urban Forest Supervisor SUBJECT: Removal Application SR#14072 On August 14, 2023, I Posted a Public Notice for a Tree Committee hearing for one Blackwood Acacia tree(s) located at 1414 Santa Rosa Street in response to tree removal application SR#14072. The removal of the mentioned application was submitted based on: San Luis Obispo Municipal Code 12.24.090 (E) 3 E. 3. Tree removal requests based on property owner convenience shall be subject to tree committee review in accordance with the process set forth in subsection (F)(2) of this section, the relevant additional application requirements set forth in subsection (D)(2) of this section, and the criteria set forth in subsection G of this section. The Subject tree(s) one Blackwood Acacia (Acacia melanoxylon) The tree committee shall review and make a recommendation on the tree removal application to the Community Development Director. authorized by the City of San Luis Obispo Municipal Code, Title 12, Tree Regulations Thank you, Anthony Whipple, Acting City Arborist/Urban Forest Supervisor (805) 781-7021 awhipple@slocity.org Public Works - Urban Forestry 25 Prado Road, San Luis Obispo, CA 93401-3218 805.781.7220 slocity.org Page 23 of 59 Page 24 of 59 Page 25 of 59 Page 26 of 59 Page 27 of 59 XPage 28 of 59 Page 29 of 59 Page 30 of 59 TREE COMMITTEE INFORMATIONAL UPDATE DATE: August 17, 2023 TO: Tree Committee Members FROM: Anthony Whipple, Acting City Arborist/Urban Forest Supervisor (805) 781-7021 awhipple@slocity.org SUBJECT: Mitchell Park Heritage Ash Tree Level 3 Risk Assessment BACKGROUND In June, City staff contracted with West Coast Arborist (WCA) to conduct a Level 3 Tree Risk Assessment (Attachment A) on the Heritage Ash Tree located in Mitchell Park, 1400 Osos Street. The assessment was in response to staff observations of the tree’s declining health and the pending park improvements planned within the critical root zone of the tree. Based on the recommendations within the report from WCA, and the location of the tree within proximity of the Senior Center and park playground, the City will be pursuing removal of the tree based on the following criteria: Tree Regulations 12.24.090E(1)(b) 1. The city arborist may authorize a tree removal upon receipt of a removal application pursuant to subsection D of this section and issue a tree removal permit upon determination of any of the following circumstances: b. The tree is dead or dying or diseased or damaged beyond reclamation. The City will pursue this removal through the process described within Municipal Code Chapter 12.24 (Tree Regulations); an application will be submitted, and signage will be posted in a prominent location notifying the public of the date and description of a proposed tree removal. Members of the public are given 10 days from the date of posting to appeal the City Arborist’s decision. COMMITTEE PURVIEW This update is strictly informational, and no decision is required from the Tree Committee at this time. If appealed within the window of time during the formal process, the item will be added to the next available Tree Committee agenda and the Committee will be the final decision maker for the removal request. ATTACHMENTS A - Mitchell Park Ash Tree Level 3 Risk Assessment Meeting Date: 8/28/2023 Item Number: 5a Time Estimate: 30 minutes Page 31 of 59 Page 32 of 59 City of San Luis Obispo Level 3 Risk Assessment Shamel Ash SUBMITTED TO: Anthony Whipple City of San Luis Obispo PREPARED BY: Leonardo Tuchman Plant Health Care Arborist ISA Certified Arborist WE-12453A ASCA Registered Consulting Arborist #771 ISA Tree Risk Assessment Qualified California DPR QAL #146294 JULY 18TH, 2023 Page 33 of 59 Tree Care Professionals Serving Communities Who Care About Trees www.WCAINC.com Contents Summary .................................................................................................................................... 1 Introduction .............................................................................................................................. 1 Background and History ................................................................................................ 1 Assignment ........................................................................................................................... 1 Limits of the Assignment .............................................................................................. 2 Purpose and Use of the Report .................................................................................. 2 Observations ............................................................................................................................ 2 Site Description ................................................................................................................. 3 Tree Condition .................................................................................................................... 3 Site Condition ...................................................................................................................... 4 Risk Assessment ................................................................................................................... 4 Risk Assessment Methodology .................................................................................. 4 Determining Strength Loss in Tree Bases ........................................................... 4 Limitation of Tree Risk Assessment....................................................................... 5 Risk Assessment Results ............................................................................................. 6 Discussion ................................................................................................................................. 7 Conclusion ................................................................................................................................ 8 Recommendation .................................................................................................................. 8 Glossary ..................................................................................................................................... 9 Bibliography ........................................................................................................................... 10 Appendix A Map ................................................................................................................... 11 Appendix B Images ............................................................................................................ 12 Appendix C Interpretation of Level 3 Data ............................................................ 20 Appendix D Risk Rating Matrix .................................................................................... 23 Appendix E Assumptions and Limiting Conditions ........................................... 24 Appendix F Certificate of Performance .................................................................. 25 Page 34 of 59 Tree Care Professionals Serving Communities Who Care About Trees www.WCAINC.com 1 Summary In May 2023 the City of San Luis Obispo requested a comprehensive risk assessment in the form of an International Society of Arboriculture Level 3 Advanced Risk Assessment utilizing sonic tomography for one shamel ash (Fraxinus uhdei) in Mitchell Park near the senior center and children’s park. I accepted this assignment, and then performed the site visit to assess the tree on June 28th, 2023. I was joined and assisted by West Coast Arborist Inc. (WCA) consulting arborist Rebecca Mejia. My assessment returned an overall risk rating of high for the tree. The time frame for this risk assessment is one year. Introduction Background and History Mr. Anthony Whipple provided West Coast Arborist, Inc. (WCA) with authorization to create proforma #82833 to give the City the cost for this assignment. The subject tree has been growing in Mitchell Park for decades and has been observed by city staff to have fungal fruiting bodies in multiple areas and pruning wounds that have decay. The tree is valuable to the city and residents, and as such the City wants to take all measures possible before making a decision regarding removing or preserving the subject tree. Therefore, the City requested that WCA conduct sonic tomography testing on the tree to determine the internal condition of the tree’s wood in order to make a more informed decision regarding the tree’s future. Assignment The City contracted with WCA to provide these arborist services: • Level 3 Advanced Risk Assessment on one tree utilizing sonic tomography to check for internal trunk strength loss. The client’s concern is whole tree failure. • Submit one certified arborist report summarizing the assessment findings, including tomogram images and any maintenance recommendations (mitigation). • All work is to be performed per American National Standards Institute A300 (Part-9)- 2017 Tree Risk Assessment A, Tree Structure Assessment, and the International Society of Arboriculture (ISA) Best Management Practices Tree Risk Assessment, 2017. Page 35 of 59 Tree Care Professionals Serving Communities Who Care About Trees www.WCAINC.com 2 Limits of the Assignment The assignment, being a visual assessment of the subject tree, was limited to that which could be observed from the ground. Only exposed or easily exposed parts above ground level were inspected. Sonic-tomography was used to assess two cross-sectional areas of the reachable trunk. Subsurface soil conditions and tree parts below ground were not disturbed or observed. An additional limit to this assignment is that only the one tree and its immediate surroundings within and around the drip line of the tree were visually observed as part of the risk assessment. Changes to the condition of the tree because of practices or work performed by others within the dripline of the tree warrants a new risk assessment when the City of San Luis Obispo becomes aware of such practices or work by others or a change in the condition of the assessed tree. The report is not intended to be legal advice and does not represent legal advice as such. Purpose and Use of the Report The purpose of this report was to summarize the failure risk of one tree. The report is intended to be used by the City of San Luis Obispo staff that have jurisdiction and are responsible for its maintenance. Observations Rebecca and I performed the on-site visual inspection and assessment of the subject tree between 10:00 AM and 12:30 PM. The weather was cool with partial sun and no wind. I utilized the camera on my Samsung Galaxy phone issued by WCA to capture photos used in this report. Additionally, photos of fungal fruiting bodies were provided by Anthony Whipple, those photos are noted as such. A logger’s tape was used to measure diameter at standard height (DSH). This assessment utilized an Arbotom® impulse tomograph which uses the relative velocity of sound waves induced across the trunk of a tree to construct a two-dimensional picture (tomogram) that shows zones of different sound-transmission properties. The zones are color- coded and indicate degrees of mechanical strength loss. These resistance patterns indicate changes in wood density that may be caused by internal issues such as woody decay caused by fungi. An explanation of how to interpret Arbotom readings is included in Appendix C – Interpretation of Level 3 Data. Page 36 of 59 Tree Care Professionals Serving Communities Who Care About Trees www.WCAINC.com 3 Site Description The site consisted of a City park with a senior center and children’s play area on site as well. The tree is growing adjacent to the parking lot, senior center, and children's play area. Tree Condition • The subject tree is a 78-inch diameter shamel ash (Fraxinus uhdei). It has an approximate height of 65-feet, an approximate north-south spread of 60-feet, and an approximate east- west spread of 65-feet (Photo 1 and 2). • The tree canopy is healthy and dense with three large leading limbs, a southeast limb, a southwest limb, and a northwest limb. • There is a large wound on the southwest leader at 30-feet with wound wood present (Photo 3). • South side of the tree has an old pruning wound with extensive decay (Photo 4). o Anthony Whipple observed and photographed fungal fruiting bodies on this wound of the tree in September 2021. (Photo 5) Based on photographs, fungus has been identified as sulfur fungus also known as chicken-of-the-woods. o Old fungal fruiting bodies were observed at the time of visit (Photo 6). o Further sulfur fungus fruiting bodies were observed on the south side trunk of the tree in September 2021 (Photo 7). • A large decay wound from previous pruning is also present on the northwest side of the tree. Termite damage was present, and a probe went approximately 15-inches into the tree from the entrance to the wound. (Photo 8). • The southwest limb has bulging. • Multiple areas on the south side of the tree have wood/bark that indents in, indicative of buckling (Photo 9). • Sounding with a rubber mallet found multiple areas of the tree that sounded hollow. • An active hawk’s nest was present at the time of visit in the upper canopy. • The first tomogram reading was taken using 16 sensors set at the base of the trunk where the root flare begins (Photo 10). The initial readings indicated a significant amount of decay. The secondary test was performed using 15 sensors placed 4.5 feet above the ground; this test also showed significant decay within the sample area. • The first tomogram indicated that the wood quality has been significantly affected by decay and that the lower trunk area has a 38% loss of mechanical strength. This reading also indicated this loss of mechanical strength was most severe on the southwest side of the tree. The second tomogram indicated that the wood quality was also significantly affected by decay and that the test area has a 21% loss of mechanical strength. The graphs and results generated by these tests can be found in Appendix C. Page 37 of 59 Tree Care Professionals Serving Communities Who Care About Trees www.WCAINC.com 4 Site Condition • The tree is growing in a public park in a turf covered area. • Hardscape is present on the north and east side of the tree, in the form of a walking path and bench area. • City staff stated that prevailing winds in the area blow towards the southeast. Risk Assessment Risk Assessment Methodology Data collection for this project was used to derive a level of risk based on the matrices found in the ISA Best Management Practices (BMPs) for tree risk assessment (see Appendix D Tree Risk Matrix Table). The level of risk determined (low, moderate, high, or extreme) is to be used by risk managers to help in tree management decisions. When assessing risk, the value of targets is taken into consideration to categorize the consequences of failure (negligible, minor, significant, or severe). The people who use and frequent the target zone are generally the most important targets. The time frame for this report is 1 year. Determining Strength Loss in Tree Bases Two critical factors are involved in strength loss assessment in determining the likelihood of failure for a tree’s base. First, it is important to consider how much strength is lost due to the defect. Second, the load required to cause a failure must be considered. Regarding the location of the decay in the trunk, the Tree Risk Assessment Manual states: “Loss of outer wood is considered more important to stem strength than is internal decay; outer xylem tissue contributes significantly more than internal fibers to stem strength.” From Tree Structure and Mechanics Conference Proceedings: How Trees Stand Up and Fall Down: “The formulas currently available for determining strength loss in tree stems have been adopted from beam mechanics and modified to account for the inherent differences between green-wood in trees and conventional engineering materials.” However, “applying strength loss formulas from beam mechanics to trees is complicated and imprecise. Beam mechanics formulas are derived for perfect geometric shapes and bodies made of homogenous material. While a tree resembles a Page 38 of 59 Tree Care Professionals Serving Communities Who Care About Trees www.WCAINC.com 5 cylinder, it is not geometrically perfect. Similarly, wood is not a homogenous material, exhibiting a suite of variables that affect strength properties.” Strength loss formulas have yet to be precise in predicting urban tree failure. It is impossible to determine the exact remaining load-bearing capacity of a tree’s base, just as it is impossible to determine the actual and potential loads being placed on trees (e.g., dynamic wind loading). Limitation of Tree Risk Assessment Any change in site use, damage to the tree from biotic or abiotic causes, and construction work within the dripline of the tree alters the conditions which this risk assessment was performed, and thus would require that a new assessment be performed. According to the Tree Risk Assessment Manual, Second Edition, published by ISA, it is impossible to maintain trees free of risk. “There is no way to guarantee that a tree will not fail. Tree benefits increase as the age and size of trees increase; however, some level of risk must be accepted to experience the benefits provided. The goal in assessing and managing trees is to strike a balance between the risk that a tree poses and the benefits that individuals and communities derive from trees. “A considerable level of uncertainty is typically associated with tree risk assessment due to our limited ability to predict natural processes (rate of decay, response growth, etc.), weather events, traffic and occupancy rates, and potential consequences of failure. “Condition affecting trees change constantly; none of us will ever be able to predict every tree failure. Conducting a tree risk assessment neither ensures not requires perfection. Risk assessment should, however, ensure that all reasonable efforts have been made to identify the likelihood of failure, the likelihood of impact, and the consequences of failure present at the time of assessment. “Abnormally extreme storms such as tornadoes, hurricanes, and freezing rain are not predictable and, in most cases, are not considered for categorizing likelihood of failure.” Page 39 of 59 Tree Care Professionals Serving Communities Who Care About Trees www.WCAINC.com 6 Risk Assessment Results Likelihood of Failure To determine the likelihood of failure of parts of the tree, the conditions and site factors such as load on defects, rain and wind events common to the region, response growth in the tree, previous failure history, and tree health have all been considered. • For the one-year time frame the subject tree is rated as probable likelihood of failure. Likelihood of Impact When assessing the likelihood of impact, factors such as occupancy rates, the direction of fall in the target zone, and target protection were considered. The targets assessed were pedestrians, parked cars, a children’s play area, and a senior center. All are within 1X to 1.5X the height of the tree. Occupancy rates range from occasional to constant, depending on the target and the time of day. At the time of visit the children’s play area and benches around the senior center were active with people. My observations of site usage were limited to a two and a half-hour timeframe on a Wednesday morning between 10:00 am and 12:30 pm. Targets and access to the target zone cannot reasonably be restricted. • For the one-year time frame the subject tree is rated as high likelihood of impact, due to the fixed nature of the nearby structures, as well as the frequent use of pedestrians. Consequences of Failure To assess the consequences of a failure, factors such as target value, tree part size, and protection from failure parts were considered. Given the fixed nature of the senior center and children’s play area, these targets are most likely to suffer consequences of failure. People and vehicles generally only occupy the area during daylight hours. That being said, for the one-year time frame the consequences of a failure on a target are the highest for pedestrians, the rating being Severe. Risk Rating The combination of high likelihood of impact of targets with a probable likelihood of failure results in a likely rating on the first matrix. Combining the likely rating with the highest rating of consequences of failure rating of severe results in a risk rating of high risk. Page 40 of 59 Tree Care Professionals Serving Communities Who Care About Trees www.WCAINC.com 7 Discussion When considering the likelihood of failure for the subject tree, whole tree failure and major limb failure were considered. In regard to whole tree failure, the primary concern is the extensive decay that is present internally in the tree, as well as decay observed in old pruning wounds. Based on the first sonic tomographic reading, the tree has lost 38% of its wood strength with the weakest area being on the southeast side of the tree. Additionally, city staff indicated winds in the area generally blow towards southeast. Given the direction of wind and where the tree has lost wood strength, should the tree fail I believe it is likely to fall in a southeast direction. Southeast of the subject tree is the senior center and benches that were occupied during my site visit. Furthermore, the second tomographic reading indicates that there is more solid wood and subsequent wood strength above the first reading at 4.5 feet. While one might expect more wood strength to be good, this does not negate the weakened and decayed wood at the base of the tree. This solid wood puts more weight on the weakened lower portion of the tree. In addition to whole tree failure, limb failure of this tree was also considered. The tree has V- shaped attachments where all three codominant major leaders meet. Decay was observed on the pruning wounds at the base of the southeast limb and northwest limb, as well as fungal fruiting bodies that were previously on the southwest limb. City staff indicated the southeast limb was also previously pruned due to the heaviness of the limb, and the southwest limb had a limb failure that resulted in a tear out wound. Given all this, major limb failure must also be considered. Should any limb fail, the southeast limb would fail towards the senior center and nearby benches, the northwest limb would fail towards the bathrooms and children’s play area, and the southwest limb would fail towards the turf area of the park. Risk assessment is the systematic process of evaluating the potential for a tree or one of its parts to fail and cause injury to persons and/or property. The primary goal of risk assessment is to identify potentially hazardous trees so they can be treated before a failure occurs. All hazards cannot be eliminated; however, by evaluating trees and rating the associated hazards, we can attempt to prioritize and schedule pruning treatments to reduce the level of risk. Often, by the time a particular hazard is recognized, it is too late to offer any treatments except the removal of the specimen. Identifying and managing the risks associated with trees is often a subjective and complex process. Since the nature of tree failures remains rather unknown, our ability to predict which trees or their component parts will fail and in what fashion is also somewhat limited. As currently practiced, tree evaluation involves examining a given tree for structural defects, associating those defects with a known pattern of failure, then rating the degree of risk involved. Once a defect has been identified, and the owner notified, risk mitigation measures should then be discussed. Page 41 of 59 Tree Care Professionals Serving Communities Who Care About Trees www.WCAINC.com 8 Conclusion Overall while the subject shamel ash tree has a healthy dense canopy, it shows multiple signs of significant internal decay and loss of wood strength. Signs of this include old pruning wounds with observable decay, old pruning wounds with termite damage, a history of fungal fruiting bodies, bulging and buckling areas of the tree, sounding of the tree finding hollow areas, and the results of the sonic tomography showing significant decay/loss of wood strength. Furthermore, the sonic tomography testing illustrated that the lower test at the base of the tree’s root flare had less wood strength than the tomography test taken at 4.5 feet. As such, the lower portion of the trunk is weaker than the higher up areas of the trunk resulting in more weight being put on the weaker area. Major limb failure is also a concern given the decay observed on old pruning wounds and the tear out wound observed on the southwest limb. All of these factors lead to a likelihood of failure rating of probable. This combined with the occasional to constant occupancy of the site produces a high likelihood of impact rating. Considering the highest rating of consequences of impact would be severe, based on this risk assessment this tree has been designated a high-risk tree. Mitigation for this is difficult as reversing decay is not possible and decay will likely only continue as the tree continues to age. Furthermore, restricting the area around the tree is impractical due to the nature of the facilities around the tree and the large size of the tree’s target zone. Recommendation Based on observations of the tree, results of sonic tomography testing and the conclusions of the Level 3 Advanced Risk Assessment, the following mitigation is recommended: • Should the city decide to retain the tree, canopy reduction pruning should be done to reduce the weight of the tree both on major limbs and the tree as a whole. Canopy reduction reduces the load being put on the lower portion of the tree that based on sonic tomography has the most extensive decay. The residual risk would be moderate. • Perform a full tree and stump removal. Based on the level of decay detected via the tomogram readings and the observable outer decay, there is enough loss of strength that a failure can be expected to occur within one year. The residual risk would be none. WCA does not have to be the contractor for the performance of this service. o It should be noted that it is against state law to remove a raptor nest, even an inactive one. A wildlife biologist should be consulted before tree removal to confirm that this removal is in compliance with state law. The controlling authority must determine which recommended maintenance options to employ and is responsible for all scheduling of such work. All tree work shall comply with current Page 42 of 59 Tree Care Professionals Serving Communities Who Care About Trees www.WCAINC.com 9 industry standards and specifically the criteria as provided in: ISA Best Management Practices, ANSI A300 Part 1: Tree, Shrub, and Other Woody Plant Maintenance, Standard Practices, Pruning. Third Edition. Glossary Consequences of failure – Personal injury, property damage, or disruption of activities due to the failure of a tree or tree part. Drip line – Imaginary line defined by the branch spread of a single plant or group of plants. DSH-Trunk Diameter at Standard Height, 4.5 feet above ground level. High – the failed tree or tree part is likely to impact the targets. Level 3 Advanced Risk Assessment - An assessment performed to provide detailed information about specific tree parts, defects, targets, or site conditions. Specialized equipment, data collection and analysis, and/or expertise are usually required. Likelihood of Failure – The chance of a tree or tree part failure occurring within the specified time frame. Likelihood of Impact – The chance of a tree failure impacting a target during the specified time frame. Minor (Consequence)-Minor personal injury, low to moderate-value property damage, or small disruption of activities. Moderate (Risk)-Defined by its placement in the risk rating matrix; consequences are minor, and likelihood of failure is very likely or likely, or likelihood of failure is somewhat likely, and consequences are significant or severe. Negligible (Consequence)-No personal injury, low value property damage, or disruptions that can be replaced or repaired. Possible – Failure may be expected in extreme weather conditions but is unlikely during normal weather conditions within the specified time frame. Page 43 of 59 Tree Care Professionals Serving Communities Who Care About Trees www.WCAINC.com 10 Probable – Failure may be expected under normal weather conditions within the specified time frame. Residual Risk – Risk remaining after mitigation has been recommended. Response Growth-New wood produced in response to loads to compensate for higher strain in outermost fibers; includes reaction wood (compression and tension) flexure wood, and woundwood. Risk-The combination of the likelihood of an event and the severity of the potential consequences. Risk Rating-The level of risk combining the likelihood of a tree failing and impacting a specified target, and severity of the associated consequences. Sonic Tomography- Noninvasive methodology that uses sound waves to analyze the health and stability of a tree. Severe (Consequences)-Serious personal injury or death, high-value property damage, or major disruption of important activities. Significant (Consequences)-Substantial personal injury, moderate to high-value property damage, or considerable disruption of activities. Targets-People, property, or activities that could be injured, damaged, or disrupted by a tree failure. Target Zone – Location of targets in relation to tree and/or tree parts. Time frame – Time period for which an assessment is defined. Bibliography American National Standards Institute. 2017. American National Standard: Tree, Shrub, and Other Woody Plant Management – Standard Practices (Pruning) ANSI A300, (Part 1) – 2017 Pruning. Tree Care Industry Association, Londonberry, NH. 33 pp. Dunster, Julian A., E. Thomas Smiley, Nelda Matheny, and Sharon J. Lilly. 2017. Tree Risk Assessment Manual Second Edition. International Society of Arboriculture, Champaign, IL. Lilly, Sharon J., Edward F. Gilman, & E. Thomas Smiley. 2019. Best Management Practices: Pruning. Third Edition. International Society of Arboriculture, Atlanta, GA. Page 44 of 59 Tree Care Professionals Serving Communities Who Care About Trees www.WCAINC.com 11 Appendix A Map Map of Mitchell Park with subject tree noted in the red circle. Page 45 of 59 Tree Care Professionals Serving Communities Who Care About Trees www.WCAINC.com 12 Appendix B Images Photo 1: Subject shamel ash tree growing in Mitchell Park, viewed from the south side. It had a healthy dense canopy with an active hawk’s nest. On the north side of the tree is the children’s play area. Page 46 of 59 Tree Care Professionals Serving Communities Who Care About Trees www.WCAINC.com 13 Photo 2: Subject shamel ash tree viewed from the northwest side. Seen here the senior center is southeast of the subject tree and the senior center parking lot is south of the tree. Page 47 of 59 Tree Care Professionals Serving Communities Who Care About Trees www.WCAINC.com 14 Photo 3: Tear out wound observed in the southwest major codominant limb (red circle). Page 48 of 59 Tree Care Professionals Serving Communities Who Care About Trees www.WCAINC.com 15 Photo 4: Old pruning wound on the south side of the tree. Extensive decay is present in the wound. Photo 5: Photo of the same pruning wound seen in photo 2 taken in September 2021. Large fruiting bodies were present. Photo provided by Anthony Whipple. Page 49 of 59 Tree Care Professionals Serving Communities Who Care About Trees www.WCAINC.com 16 Photo 6: Old fungal fruiting bodies observed on the south side of the tree. Photo 7: Photo of the same area seen in photo 4 on the south side of the tree. Large fruiting bodies were present. Photo provided by Anthony Whipple. Page 50 of 59 Tree Care Professionals Serving Communities Who Care About Trees www.WCAINC.com 17 Photo 8: Pruning wound observed on the northwest side of the tree. Termite damage was present and a metal probe went approximately 15-inches into the wound. Red arrow indicates direction of probe. Page 51 of 59 Tree Care Professionals Serving Communities Who Care About Trees www.WCAINC.com 18 Photo 9: Wood in multiple areas of the south side of the tree had groove-like indents (red circle). This is indicative of wood buckling under weight. Page 52 of 59 Tree Care Professionals Serving Communities Who Care About Trees www.WCAINC.com 19 Photo 10: Sonic tomography equipment set up around the base of the tree for reading one. Page 53 of 59 Tree Care Professionals Serving Communities Who Care About Trees www.WCAINC.com 20 Appendix C Interpretation of Level 3 Data Test 1. This tomogram shows the 2-dimensional diagram of the trunk of the subject tree at the location where the first measurements were taken. Without knowing the weakest point of the tree trunk under external loading, every localized measurement is just an approximation. It cannot describe the mechanical behavior of the whole cross-section, trunk, or even the tree itself. This limitation is valid for all technical methods and devices in a certain way. The green area indicates rapid sound travel (measured in meters per second) and reveals intact wood. The yellow is indicative of incipient decay, and the red and purple areas represent slow sound travel and are indicative of advanced decay. This image represents advanced decay in the basal area of the subject tree, based on interruptions in the sound waves passing from one sensor to the others. Decay has breached through the cambium into the bark between sensors 1 &3, 13 & 14, 15 & 16, at sensor 13 and sensor 8. Note the “lines” running between sensors 1 & 13, 8 and 13, and 4 & 6. This type of imagery often shows an internal crack because the sound waves can’t jump across the void. Intact Wood Incipient to Moderate Decay Moderate to Advanced Decay Advanced Decay/ Cavity Page 54 of 59 Tree Care Professionals Serving Communities Who Care About Trees www.WCAINC.com 21 Test 1. The tomogram above shows the mechanical strength loss diagram of the trunk at the location where the first measurements were taken (base of trunk where it meets the root flare). There is an estimated strength loss of 38%. Given the spread of wood strength loss, the direction of a fall is most likely to be toward the southeast. This is the direction towards the senior center and parking lot. Page 55 of 59 Tree Care Professionals Serving Communities Who Care About Trees www.WCAINC.com 22 Test 2. This tomogram shows the 2-dimensional diagram of the trunk of the subject tree at the location where the second measurements were taken. Because fewer sensors were used, the alignment is slightly different. Decay appears to have breached near sensor 1 and 8. While the outer areas of the tree appear to have intact wood, the inner portion of the tree does have extensive wood loss Page 56 of 59 Tree Care Professionals Serving Communities Who Care About Trees www.WCAINC.com 23 Appendix D Risk Rating Matrix The International Society of Arboriculture tree risk assessment matrices were used for the subject tree to determine the level of risk for a one-year timeframe. Table 1 (Likelihood Matrix) is used first to determine the likelihood of failure (by categorizing the likelihood of impact to a target by a tree part in the timeframe. Table 2 (Risk Rating Matrix) references the consequences of the failure with the likelihood from Table 1 to give a risk rating for the tree(s). Likelihood Matrix Likelihood of Impacting Target Likelihood of Failure Very Low Low Medium People/cars High buildings/play area Imminent Unlikely Somewhat Likely Likely Very Likely Probable-trunk Unlikely Unlikely Somewhat likely Likely Possible - major limb Unlikely Unlikely Unlikely Somewhat Likely Improbable Unlikely Unlikely Unlikely Unlikely Risk Rating Matrix Consequences of Target Impact Likelihood of Failure & Impact Negligible Minor-buildings Significant- buildings/play area Severe- people/cars Very Likely Low Moderate High Extreme Likely-buildings/play area Low Moderate High High Somewhat Likely- people/cars Low Low Moderate Moderate Unlikely Low Low Low Low Page 57 of 59 Tree Care Professionals Serving Communities Who Care About Trees www.WCAINC.com 24 Appendix E Assumptions and Limiting Conditions 1. Care has been taken to obtain all information from reliable sources. All data has been verified insofar as possible; however, the Consultant can neither guarantee nor be responsible for the accuracy of information provided by others. Standard of Care has been met with regards to this project within reasonable and normal conditions. 2. The Consultant will not be required to give testimony or to attend court due to this report unless subsequent contractual arrangements are made, including payment of an additional fee for such services as described in the fee schedule and contract of engagement. 3. Loss or alteration of any part of this report invalidates the entire report. 4. Possession of this report or a copy thereof does not imply right of publication or use for any purpose by any other than the person to whom it is addressed, without the prior written consent of the Consultant. 5. This report and any values expressed herein represent the opinion of the Consultant, and the Consultant’s fee is in no way contingent upon the reporting of a stipulated result, a specified value, the occurrence of a subsequent event, nor upon any finding to b e reported. 6. Unless expressed otherwise: 1) information contained in this report covers only those items that were examined and reflects t he condition of those items at the time of inspection; and 2) the inspection is limited to visual examination of accessible items without dissection, excavation, or coring, unless otherwise stated. There is no warranty or guarantee, expressed or implied, that pro blems or deficiencies of the tree(s) or property in question may not arise in the future. 7. Arborists are tree specialists who use their education, knowledge, training, and experience to examine trees, recommend measures to enhance the beauty and health of trees, and attempt to reduce the risk of living near trees. It is highly recommended that you follow the arborist recommendations; however, you may choose to accept or disregard the recommendations and/or seek additional advice. 8. Arborists cannot detect every condition that could possibly lead to the structural failure of a tree. Trees are living organ isms that fail in ways we do not fully understand. Conditions are often hidden within trees and below ground. Arborists cannot guarante e that a tree will be healthy or safe under all circumstances, or for a specific period. 9. Any recommendations and/or performed treatments (including, but not limited to, pruning or removal) of trees may involve considerations beyond the scope of the arborist’s services, such as property boundaries, property ownership, site lines, disp utes between neighbors, and any other related issues. Arborists cannot take such considerations into account unless complete and accurate information is disclosed to the arborist. An arborist can then be expected to consider and reasonably rely on the completeness and accuracy of the information provided. 10. The author has no personal interest or bias with respect to the subject matter of this report or the parties involved. He/she has inspected the subject tree(s) and to the best of their knowledge and belief, all statements and information presented in the report are true and correct. 11. Unless otherwise stated, trees were examined using the tree risk assessment criteria detailed by ANSI A300 (Part 9)-2017 Tree Risk Assessment, a. Tree Structure Assessment. Page 58 of 59 Tree Care Professionals Serving Communities Who Care About Trees www.WCAINC.com 25 Appendix F Certificate of Performance I, Leonardo Tuchman certify that: •I have personally inspected the trees referred to in this report and have stated my findings accurately. The extent of the assessment is stated in the attached report and the Limits of the Assignment. •I have no current or prospective interest in the tree or the property that are the subject of this report and have no personal interest or bias with respect to the parties involved. •The analysis, opinions, and conclusions stated herein are my own and are based on current scientific procedures and facts. •My analysis opinions, and conclusions were developed, and this report has been prepared according to commonly accepted arboricultural practices. •No one provided significant professional assistance to me, except as indicated within the report. •My compensation is not contingent upon the reporting of a predetermined conclusion that favors the cause of the client or any other party nor upon the results of the assessment, the attainment of stipulated results, or the occurrence of any subsequent events. I further certify that I am a member of good standing of the American Society of Consulting Arborists, and the International Society of Arboriculture. I have been involved in the field of arboriculture in a full-time capacity for a period of more than five years. Respectfully, Leonardo Tuchman Plant Health Care Arborist West Coast Arborists Inc. ISA Certified Arborist WE-12453A ASCA Registered Consulting Arborist #771 ISA Tree Risk Assessment Qualified California DPR QAL #146294 Page 59 of 59