Arborist Report. Attachment Buena Vista Avenue Walnut Creek, CA Y PREPARED FOR Larson Shores 1940 Union Street #22 Oakland, CA

Transcription

1 Attachment 3 Arborist Report 2360 Buena Vista Avenue Walnut Creek, CA PREPARED FOR Larson Shores 1940 Union Street #22 Oakland, CA PREPARED BY: 325 Ray St. Pleasanton, CA December 8, 2016 Y Received

2 Arborist Report 2360 Buena Vista Avenue Walnut Creek, CA Table of Contents Page Introduction and Overview 1 Tree Assessment Methods 1 Description of Trees 2 Suitability for Preservation 4 Evaluation of Impacts and Recommendations for Action 5 Appraisal Value 6 Tree Preservation Guidelines 7 List of Tables Table 1: Tree condition & frequency of occurrence. 2 Table 2: Tree suitability for preservation. 5 Table 3: Proposed action. 6 Table 4: Appraisal of value. 7 Tree Assessment Map Tree Assessment Form Exhibits

3 Arborist Report 2360 Buena Vista Avenue Walnut Creek, CA Introduction and Overview Larson Shores is seeking to redevelop the site located at 2360 Buena Vista Avenue in Walnut Creek, CA. The site currently consists of a single-family residence, a detached garage, deck, play structure and garden area. was asked to prepare a Preliminary Arborist Report for the site part of submittal for development to the City of Walnut Creek. This report provides the following information: 1. An evaluation of the health and structural condition of the trees within the proposed project area based on a visual inspection from the ground. 2. An assessment of the trees that will be preserved and removed based on the construction plans. 3. An appraisal value of the trees according to the procedures described in the Guide for Plant Appraisal (Council of Tree and Landscape Appraisers). 4. Guidelines for tree preservation during the design, construction and maintenance phases of development. Tree Assessment Methods Trees were assessed on December 2, The survey included all trees with a diameter of nine inches or greater that may be affected by the proposed development. Access to some trees was limited by a wall and a fence. Trees that could not be accessed were given a tree number but no tag was attached to the trunk. The assessment procedure consisted of the following steps: 1. Identifying the tree as to species; 2. Tagging each tree with an identifying number and recording its location on a map; 3. Measuring the trunk diameter at a point 4.5 above grade; 4. Evaluating the health and structural condition using a scale of 1 5: 5 - A healthy, vigorous tree, reasonably free of signs and symptoms of disease, with good structure and form typical of the species. 4 - Tree with slight decline in vigor, small amount of twig dieback, minor structural defects that could be corrected. 3 - Tree with moderate vigor, moderate twig and small branch dieback, thinning of crown, poor leaf color, moderate structural defects that might be mitigated with regular care. 2 - Tree in decline, epicormic growth, extensive dieback of medium to large branches, significant structural defects that cannot be abated. 1 - Tree in severe decline, dieback of scaffold branches and/or trunk; most of foliage from epicormics; extensive structural defects that cannot be abated. 5. Rating the suitability for preservation as high, moderate or low. Suitability for preservation considers the health, age and structural condition of the tree, and its potential to remain an asset to the site for years to come.

4 Larson Shores ~ December 8, 2016 Page 2 Description of Trees Nine (9) trees were evaluated, representing eight species (Table 1). Trees #183, 188 and 189 were located off-site but close to the property line. Tree species were typical of those found in Bay Area landscapes. Coast live and valley oak are native to the Walnut Creek area and may be indigenous to the site. Trees were generally in good condition. Descriptions of each tree are found in the Tree Assessment Form and approximate locations are plotted on the Tree Assessment Plan (see Exhibits). Table 1. Condition ratings and frequency of occurrence Buena Vista Avenue ~ Walnut Creek, CA. Common Name Scientific Name Condition Total Poor (1-2) Fair (3) Good (4-5) Silver maple Acer saccharinum Olive Olea europaea Italian stone pine Pinus pinea Coast live oak Quercus agrifolia Valley oak Quercus lobata California pepper Schinus molle Coast redwood Sequoia sempervirens Siberian elm Ulmus pumila Total Coast live oak (#187) and silver maple (#186) were located along the southern property line adjacent to a 3 tall block retaining wall. Both trees were mature in development with trunk diameter of 29. Coast live oak #187 was in excellent condition; the silver maple was good condition. Both trees had spreading form and vigorous growth (Photo 1 and 2). Photo 1, left. Coast live oak #187 was in excellent condition with good structure and vigorous growth. Photo 2, right. Silver maple #186 was in good condition with spreading form and good growth.

5 Larson Shores ~ December 8, 2016 Page 3 Four trees were located in the northeast corner of the site: European olives #184 and 185, Italian stone pine #182, and coast redwood #181. The olives were in good (#184) and fair (#185) condition. Both had multiple attachments at the base. Overall vigor was good but growth was suppressed by near-by trees. The Italian stone pine was in good condition and mature in development with a 24 diameter. The stone pine had a significant lean but was vigorous. The redwood was mature with a 26 diameter and was in poor condition with very little live foliage. Three off-site trees were evaluated: valley oak #183; California pepper #188 and Siberian elm #189. All three were mature with trunk diameters greater than 20. The California pepper was behind a wall and the diameter was estimated (Photo 3). The valley oak and California pepper were in good condition with multiple attachments, spreading form and good vigorous growth. The Siberian elm was in good condition with good vigorous growth despite the history of improper maintenance (Photo 4). Photo 3, left. California pepper #188 was in good condition. Photo 4, right. Siberian elm #189 had good vigor despite the history of improper maintenance. The City of Walnut Creek Tree Preservation Ordinance No defines a Highly Protected tree as any of the following type of tree species: valley oak (Quercus lobata), blue oak (Q. douglasii), coast live oak (Q. agrifolia), California black oak (Q. kelloggii), canyon live oak (Q. chrysolepis), interior live oak (Q wilizenii), madrone (Arbutus menziesii), California buckeye (Aesculus californica), California black walnut (Juglans hindsii), and grey pine (Pinus sabiniana) with a trunk diameter of nine inches or greater. Trees (#183 and 187) meet the criteria for a Highly-Protected tree.

6 Larson Shores ~ December 8, 2016 Page 4 Suitability for Preservation Before evaluating the impacts that will occur during development, it is important to consider the quality of the tree resource itself, and the potential for individual trees to function well over an extended length of time. Trees that are preserved on development sites must be carefully selected to make sure that they may survive development impacts, adapt to a new environment and perform well in the landscape. Our goal is to identify trees that have the potential for long-term health, structural stability and longevity. For trees growing in open fields, away from areas where people and property are present, structural defects and/or poor health presents a low risk of damage or injury if they fail. However, we must be concerned about safety in use areas. Therefore, where development encroaches into existing plantings, we must consider their structural stability as well as their potential to grow and thrive in a new environment. Where development will not occur, the normal life cycles of decline, structural failure and death should be allowed to continue. Evaluation of suitability for preservation considers several factors: Tree health Healthy, vigorous trees are better able to tolerate impacts such as root injury, demolition of existing structures, changes in soil grade and moisture, and soil compaction than are non-vigorous trees. Coast live oak (#187) was in excellent condition and would be well suited for retention. Structural integrity Trees with significant amounts of wood decay and other structural defects that cannot be corrected are likely to fail. Such trees should not be preserved in areas where damage to people or property is likely. Coast redwood (#181) was all but dead, and is not a good candidate for retention, immaterial of construction impacts. Species response There is a wide variation in the response of individual species to construction impacts and changes in the environment. Olives and coast live oaks are tolerant of construction impacts, whereas silver maple is not. Tree age and longevity Old trees, while having significant emotional and aesthetic appeal, have limited physiological capacity to adjust to an altered environment. Young trees are better able to generate new tissue and respond to change. Species invasiveness Species that spread across a site and displace desired vegetation are not always appropriate for retention. This is particularly true when indigenous species are displaced. The California Invasive Plant Inventory Database ( lists species identified as being invasive. Walnut Creek is part of the Central West Floristic Province. California pepper is listed as having limited invasiveness potential.

7 Larson Shores ~ December 8, 2016 Page 5 Each tree was rated for suitability for preservation based upon its age, health, structural condition and ability to safely coexist within a development environment (see Tree Assessment Forms in Exhibits, and Table 2). Table 2: Tree suitability for preservation Buena Vista Avenue ~ Walnut Creek, CA. High Trees in this category are in good health and have structural stability and the potential for longevity at the site. Three (3) trees were rated as having high suitability for preservation: California pepper #188; coast live oak #187 and valley oak #183. Moderate Trees in this category have fair health and/or structural defects that may be abated with treatment. These trees require more intense management and monitoring, and may have shorter life-spans than those in the high category. Five (5) trees were rated as having moderate suitability for preservation: olives #184 and 185; Italian stone pine #182; Siberian elm #189 and silver maple #186. Low Trees in this category are in poor health or have significant defects in structure that cannot be abated with treatment. These trees can be expected to decline regardless of management. The species or individual tree may possess either characteristics that are undesirable in landscape settings or be unsuited for use areas. Coast redwood #181 was rated as having low suitability for preservation. We consider trees with high suitability for preservation to be the best candidates for preservation. We do not recommend retention of trees with low suitability for preservation in areas where people or property will be present. Retention of trees with moderate suitability for preservation depends upon the intensity of proposed site changes. Evaluation of Impacts and Recommendations for Action Appropriate tree retention develops a practical match between the location and intensity of construction activities and the quality and health of trees. The Tree Assessment was the reference point for tree condition and quality. I used the Proposed Site Plan L2, produced by Josh Larson at Larson Shores to assess impacts from construction. The plan was not dated. Surveyed trunk locations were only available for trees #186 and 187. The proposed project would completely redevelop the site, essentially from property line to property line. The existing structures and other improvements would be demolished. Four high-density residential units would be constructed. No grading or utility information was reviewed. That said, grading and excavation for the four units will leave little opportunity for preservation of on-site trees.

8 Larson Shores ~ December 8, 2016 Page 6 Based on my assessment and review of the project plans, I recommend preservation of coast live oak #187 and the three off site trees (#183, 188 and 189) (Table 3). Based on the plan removal will be necessary for the five remaining trees due to impacts from construction. Retention of coast live oak #187 is detailed on the site plan. Preservation of this tree requires retention of the existing block wall (see Photo 1). The tree is depicted with a 15 wide canopy. But the existing canopy is larger and will require pruning to accommodate unit 4. A driveway constructed of permeable pavers is approximately 10 from the trunk. Given the lack of grading information, I cannot assess impacts from the driveway construction. I recommend the edge of the driveway be moved at least 10 from the trunk of the tree. Recommendations for preservation are predicated on adherence to the Tree Preservation Guidelines detailed in a subsequent section. The City of Walnut Creek requires a dripline encroachment permit for cases where one needs to work within the dripline. This permit will be required for trees #183, The City of Walnut Creek requires a permit to remove any tree with a trunk diameter of nine inches or greater. A tree removal permit will be required for trees #181, 182, 184, 185 and 186. Table 3. Proposed Action Buena Vista Avenue ~ Walnut Creek, CA. Tree No. Species Trunk Diameter (in.) Highly Protected Disposition Comments 181 Coast redwood 26 No Remove Tree removed based on condition. 182 Italian stone pine 24 No Remove Within building footprint. 183 Valley oak 17 Yes Preserve Off-site; with a 10' overhang. 184 Olive 9,5,2 No Remove Grade change will remove tree. 185 Olive 7,7,5,5,4,3,3,2 No Remove Grade change will remove tree. 186 Silver maple 29 No Remove Vertical clearance needed for preservation not available. 187 Coast live oak 29 Yes Preserve (with impacts) 10 from root pruning and eight feet vertical clearance will be required. 188 California pepper Unknown No Preserve Off-site; with a 12' overhang. 189 Siberian elm 24,18 No Preserve Off-site; with a 17' overhang.

9 Larson Shores ~ December 8, 2016 Page 7 Appraisal Value The City of Walnut Creek requires an estimate of value be prepared for trees on the property. In appraising the value of the trees, we employed the standard methods found in Guide for Plant Appraisal, 9th edition (International Society of Arboriculture, Champaign IL, 2000). In addition, we referred to Species Classification and Group Assignment (2004), a publication of the Western Chapter of the International Society of Arboriculture. These two documents outline the methods employed in tree appraisal. The value of landscape trees is based on four factors: size, species, condition and location. Size is measured as trunk diameter, normally 54" above grade. The species factor considers the adaptability and appropriateness of the plant in the East Bay area. The Species Classification and Group Assignment lists recommended species ratings. Condition reflects the health and structural integrity of the individual. The location factor considers the site, placement and contribution of the tree in its surrounding landscape. The appraised value of each tree is included in the Tree Assessment Form. The value of the nine trees was $51,850. The value of the trees proposed for removal is $21,350. Table 4: Appraised Value Buena Vista Avenue. Walnut Creek, CA Tree No. Species Trunk Diameter (in.) Highly Protected Tree Appraised Value 181 Coast redwood 26 No $1, Italian stone pine 24 No $7, Valley oak 17 Yes $7, Olive 9,5,2 No $1, Olive 7,7,5,5,4,3,3,2 No $1, Silver maple 29 No $10, Coast live oak 29 Yes $21, California pepper Unknown No No Value 189 Siberian elm 24,18 No $1,350 Total $51,850

10 Larson Shores ~ December 8, 2016 Page 8 Tree Preservation Guidelines The goal of tree preservation is not merely tree survival during development but maintenance of tree health and beauty for many years. Trees retained on sites that are either subject to extensive injury during construction or are inadequately maintained become a liability rather than an asset. The response of individual trees depends on the amount of excavation and grading, care with which demolition is undertaken, and construction methods. Coordinating any construction activity inside the TREE PROTECTION ZONE can minimize these impacts. The following recommendations will help reduce impacts to trees from development and maintain and improve their health and vitality through the clearing, grading and construction phases. Tree Preservation Guidelines, prepared by the Consulting Arborist, should be included on all plans. Design recommendations 1. Any changes to the plans affecting the trees should be reviewed by the consulting arborist with regard to tree impacts. These include, but are not limited to, site plans, improvement plans, utility and drainage plans, grading plans, landscape and irrigation plans, and demolition plans. 2. Plot accurate locations of all trees to be preserved on all project plans. 3. Plan for tree preservation by designing adequate space around trees to be preserved. This is the TREE PROTECTION ZONE: No grading, excavation, construction or storage of materials should occur within that zone. Route underground services including utilities, sub-drains, water or sewer around the TREE PROTECTION ZONE. a. The TPZ for on-site tree #187 shall be 10. b. The TPZ for off-site trees #188 and 189 five feet from the property line. c. The TPZ for tree #183 shall be the property line. 4. Underground services including utilities, sub-drains, water or sewer shall be routed around the TREE PROTECTION ZONE. Where encroachment cannot be avoided, special construction techniques such as hand digging or tunneling under roots shall be employed where necessary to minimize root injury. 5. Any herbicides placed under paving materials must be safe for use around trees and labeled for that use. 6. Do not lime the subsoil within 50 of any tree. Lime is toxic to tree roots. 7. As trees withdraw water from the soil, expansive soils may shrink within the root area. Therefore, foundations, footings and pavements on expansive soils near trees should be designed to withstand differential displacement. 8. Ensure adequate but not excessive water is supplied to trees; in most cases, occasional irrigation will be required. Avoid directing runoff toward trees.

11 Larson Shores ~ December 8, 2016 Page 9 Pre-construction treatments and recommendations 1. The demolition contractor shall meet with the Consulting Arborist before beginning work to discuss work procedures and tree protection. 2. Fence trees to completely enclose the TREE PROTECTION ZONE prior to demolition, grubbing, or grading. Fences shall be 6 ft. chain link or equivalent as approved by the City of Walnut Creek. a. The TPZ for on-site tree #187 shall be 10. b. The TPZ for off-site trees #188 and 189 five feet from the property line. c. The TPZ for tree #183 shall be the property line. Fences are to remain until all construction is completed. 3. Branches extending into the work area that can remain following demolition shall be tied back and protected from damage. 4. Trees to be preserved may require pruning to provide construction clearance. All pruning shall be completed by a Certified Arborist or Tree Worker. Pruning shall adhere to the latest edition of the ANSI Z133 and A300 standards as well as the Best Management Practices -- Tree Pruning published by the International Society of Arboriculture. Consulting arborist shall be present during pruning. 5. Apply and maintain 4-6 wood chip mulch within the TREE PROTECTION ZONE. Keep the mulch 2 from the base of tree trunks. 6. Tree(s) to be removed that have branches extending into the canopy of tree(s) to remain must be removed by a qualified arborist and not by construction contractors. The qualified arborist shall remove the tree in a manner that causes no damage to the tree(s) and understory to remain. Tree stumps shall be ground 12 below ground surface. 7. Trees to be removed shall be felled so as to fall away from TREE PROTECTION ZONE and avoid pulling and breaking of roots of trees to remain. If roots are entwined, the Consulting Arborist may require first severing the major woody root mass before extracting the trees, or grinding the stump below ground. 8. All tree work shall comply with the Migratory Bird Treaty Act as well as California Fish and Wildlife code to not disturb nesting birds. To the extent feasible tree pruning and removal should be scheduled outside of the breeding season. Breeding bird surveys should be conducted prior to tree work. Qualified biologists should be involved in establishing work buffers for active nests.

12 Larson Shores ~ December 8, 2016 Page 10 Recommendations for tree protection during construction 1. Prior to beginning work, the contractors working in the vicinity of trees to be preserved are required to meet with the Consulting Arborist at the site to review all work procedures, access routes, storage areas, and tree protection measures. 2. All contractors shall conduct operations in a manner that will prevent damage to trees to be preserved. 3. Any grading, construction, demolition or other work that is expected to encounter tree roots should be monitored by the Consulting Arborist. 4. Fences are to remain until all site work has been completed. Fences may not be relocated or removed without permission from/discussion with the Consulting Arborist. 5. Construction trailers, traffic and storage areas must remain outside fenced areas at all times. 6. Structures and underground features to be removed within the TREE PROTECTION ZONE shall use the smallest equipment, and operate from outside the TREE PROTECTION ZONE. The consultant shall be on-site during all operations within the TREE PROTECTION ZONE to monitor demolition activity. 7. Any root pruning required for construction purposes shall receive the prior approval of and be supervised by the Consulting Arborist. 8. Any demolition or excavation within the dripline or other work that is expected to encounter tree roots should be approved and monitored by the Consulting Arborist. Roots shall be cut by manually digging a trench and cutting exposed roots with a sharp saw. The Consulting Arborist will identify where root pruning is required. 9. If injury should occur to any tree during construction, it should be evaluated as soon as possible by the Consulting Arborist so that appropriate treatments can be applied. 10. Any additional tree pruning needed for clearance during construction must be performed by a Certified Arborist or Certified Tree Worker and not by construction personnel. Maintenance of impacted trees Trees preserved at the site will experience a physical environment different from that predevelopment. As a result, tree health and structural stability should be monitored. Occasional pruning, fertilization, mulch, pest management, replanting and irrigation may be required. In addition, provisions for monitoring both tree health and structural stability following construction must be made a priority. As trees age, the likelihood of branches or entire trees failing will increase. Therefore, annual inspection for hazard potential is recommended. If you have any questions regarding my observations or recommendations, please contact me. Darya Barar Certified Arborist WE-6757A

13 Exhibits Tree Assessment Map Tree Assessment Form

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15 Tree Assessment 2360 Buena Vista Ave Walnut Creek, CA December 2, 2016 Tree No. Species Trunk Diameter (in.) Protected Tree? Condition 1=poor 5=excellent Suitability for Preservation Comments 181 Coast redwood 26 No 1 Low Little live foliage; all but dead. 182 Italian stone pine 24 No 4 Moderate Leaning trunk; heavy healthy growth. 183 Valley oak 17 Yes 4 High Off-site no tag; overhanging site by 10'; spreading form; good growth and structure. 184 Olive 9,5,2 No 4 Moderate Multiple attachments arise from base; mound at base; suppressed; good healthy growth only at top. 185 Olive 7,7,5,5,4,3 No 3 Moderate Multiple attachments arise from base; suppressed; good growth.,3,2 186 Silver maple 29 No 4 Moderate Multiple attachments arise from 10'; spreading form; good growth. 187 Coast live oak 29 Yes 5 High Spreading form; good dense growth. 188 California pepper -- No 4 High Off-site no tag; overhangs property by 12'; multiple attachments; spreading form; good growth. 189 Siberian elm 24,18 No 3 Moderate Off-site no tag; overhangs property by 17'; multiple attachments arise from base; spreading form; history of improper maintenance; decay.