UPDATED TREE REPORT 470 and 498 Corona Road Petaluma, CA

Transcription

1 HORTICULTURE ARBORICULTURE URBAN FORESTRY UPDATED TREE REPORT 470 and 498 Corona Road Petaluma, CA PREPARED FOR: DRG Builders 3480 Buskirk Avenue, Suite 200 Pleasant Hill, CA PREPARED BY: 4125 Mohr Ave., Suite F Pleasanton, CA July Rheem Dr., Suite A Pleasanton, CA phone fax

2 Updated Tree Report 470 and 498 Corona Road Petaluma, CA Table of Contents Page Introduction and Overview 1 Survey Methods 1 Description of Trees 2 Suitability for Preservation 3 Evaluation of Impacts and Recommendations for Preservation 6 Appraisal of Value 7 Mitigation Requirements 8 Tree Preservation Guidelines 9 List of Tables Table 1. Condition ratings and frequency of occurrence for trees 3 Table 2. Tree suitability for preservation 4 Table 3. Recommendations for Action 6 Table 4. Appraised value of Protected trees to be preserved 8 Table 5. Appraised value of Protected trees to be removed 8 Table 6. Mitigation calculations 9 Tree Assessment Forms Attachments Tree Assessment Map

3 Updated Tree Report, July 2011 Page 1 Introduction and Overview DRG Builders are proposing to redevelop the properties at 470 and 498 Corona Road, in Petaluma. The plans propose to construct 31 residential units across the two sites. was asked to visit the site to update tree condition data and revised the original Tree Reports prepared for the sites for review by the City of Petaluma. This report provides the following information: 1. An updated evaluation of the health and structural condition of the trees from a visual inspection. 2. An evaluation of the impacts of the proposed development on the trees. 3. Recommendations for tree preservation and protection during all phases of construction. 4. The appraised value of the Protected trees. 5. Mitigation calculations. Survey Methods I visited the site on April 22, The survey included all trees 4 and greater in diameter. The survey 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 54 above grade; 4. Evaluating the health and structural condition using a scale of 0 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. 0 Dead. 5. Rating the suitability for preservation as good, moderate or poor. Suitability for preservation considers the health, age and structural condition of the tree species, and its potential to remain an asset to the site for years to come. Good: Trees with good health and structural stability that have the potential for longevity at the site. Moderate: Trees with somewhat declining health and/or structural defects than can be abated with treatment. The tree will require more intense management and monitoring, and may have shorter life span than those in good category. Poor: Trees in poor health or with significant structural defects that cannot be mitigated. Tree is expected to continue to decline, regardless of treatment. The species or individual tree may have characteristics that are undesirable for landscapes, and generally are unsuited for use areas.

4 Updated Tree Report, July 2011 Page 2 Description of Trees Thirty-five (35) trees were originally assessed in 2005, 28 of which remain. Five (5) of the surveyed trees were located within the right of way along Corona Road (#1 and 23-26), and Monterey cypress #34 was growing on the western fence-line. Following is a brief summary of the changes between the time of our 2005 survey and the current survey: Seven (7) of the trees had been removed, including #9, 14, 17, 22, and 35. Twenty-eight (28) of the trees were present on the site, including #1-8, 10-13, 15, 16, 18-21, 23-26, 28-31, 33 and 34) The condition of 14 of the remaining trees had changed. The condition of all 14 trees was downgraded, including #3, 8, 10-13, 15, 16, 18, 19, 21, 23, 26 and 34. Generally, trees had grown 1-2 in diameter. Fourteen (14) species were represented at the site (Table 1, following page). The most frequently occurring species was coast live oak, with nine (9) trees or 32% of the population, followed by English walnut (3 trees, or 11%). English walnuts were part of a row of five (5) orchard trees (#16 and 18-21) planted west of the 498 Corona Rd. residence. Average tree condition was poor (14 trees, or 50% of the population), with five (5) trees rated in fair condition (18%), and nine (9) in good (32%). Average trunk diameter was 21. Fourteen (14) trees had multiple trunks arising below the 54 measurement point. Eight (8) coast live oaks remained around the existing residences. Three (3) of the coast live oaks were mature, with diameters between 27 and 30, and six (6) were young, with diameters between 3 and 15. Coast live oaks #22 and 27 died in the time since our 2005 survey. Several trees growing east of the 498 Corona Rd. residence had been pruned for utility line clearance. Pruning had affected the health and condition of several of the trees. Trees at the southeast corner of the building had been topped and had poor form and structure (#10-12). Tree #9 had been removed since the time since our 2005 survey. Three Lombardy poplars along Corona Rd. (#24-26) were in poor condition. All had extensive trunk decay and #25 and 26 had recently experienced stem failures (Photo 1). Decay was noted in Siberian elm #31 (#32 had been removed), and Calif. black locust #33 had a large basal cavity with extensive decay. Photo 1: Lombardy poplars were in poor condition, with extensive trunk decay. Stems of #25 and 26 had recently failed (arrow).

5 Updated Tree Report, July 2011 Page 3 Two Canary Island date palms (#29 and 30), rated in excellent condition, were the two best trees on site. In contrast, the Monterey cypress #34, growing on the southwestern fence line, was in poor condition, with a history of recent branch failure. The City of Petaluma defines native oak species with diameters of 4 or greater, Calif. buckeye 6 in diameter and greater, Calif. bay 12 in diameter and greater, coast redwoods 18 and greater, and right-of-way trees as Protected. Based on this definition, 12 trees, including the five (5) right-of-way trees (#1 and 23-26) qualified as Protected. Protected trees are listed in the attached Tree Survey Forms. Table 1: Condition ratings and frequency of occurrence of trees. 470 and 498 Corona Rd., Petaluma CA Common Name Scientific Name Condition Rating No. of Poor Fair Good Trees (1-2) (3) (4-5) Monterey cypress Cupressus macrocarpa Modesto ash Fraxinus valutina var glabra 'Modesto' Calif. black walnut Juglans hindsii English walnut Juglans regia Sweet gum Liquidambar styraciflua Apple Malus domestica Canary Island palm Phoenix canariensis Lombardy poplar Populus nigra 'Italica' Catalina cherry Prunus caroliniana Bradford pear Pyrus callaryana 'Bradford' Coast live oak Quercus agrifolia Calif. black locust Robinia pseudoacacia Coast redwood Sequoia sempervirens Siberian elm Ulmus pumila Total % 18% 32% 100% 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.

6 Updated Tree Report, July 2011 Page 4 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. 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. Species response There is a wide variation in the response of individual species to construction impacts and changes in the environment. In our experience, for example, English walnuts are sensitive to construction impacts, while coast live oak is tolerant of site disturbance. 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. Invasiveness Species which spread across a site and displace desired vegetation are not always appropriate for retention. This is particularly true when indigenous species are displaced. Species identified in this report rarely reproduce in landscape settings. Each tree was rated for suitability for preservation based upon its age, health, structural condition and ability to safely coexist within a development environment (Table 2). We consider trees with good 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. Table 2: Tree Suitability for Preservation 470 and 498 Corona Rd., Petaluma CA Good These are trees with good health and structural stability that have the potential for longevity at the site. Three (3) trees were rated as having good suitability for preservation. Tree No. Species Diameter (in.) 23 Coast live oak Canary Island palm Canary Island palm 31 (Continued, next page)

7 Updated Tree Report, July 2011 Page 5 Table 2: Tree Suitability for Preservation, continued 470 and 498 Corona Rd., Petaluma CA Moderate Trees in this category have fair health and/or structural defects that may be abated with treatment. Trees in this category require more intense management and monitoring, and may have shorter life-spans than those in the good category. Nine (9) trees were rated as having moderate suitability for preservation. Tree No. Species Diameter (in.) 1 Coast live oak 15 2 Coast live oak 30,27 3 Coast live oak 29 4 Coast live oak 12 5 Coast live oak 8,7 6 Coast live oak 8,3 7 Coast live oak 10,6 8 Coast live oak Calif. black walnut 15,7 Poor 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. Sixteen (16) trees were rated as having poor suitability for preservation. Tree No. Species Diameter (in.) 10 Coast redwood Modesto ash Sweet gum Coast redwood 5 16 English walnut 5,5,4,4,4 18 English walnut 5,5,4,4 19 English walnut 7,5,3 20 Bradford pear 6,5,5,4 21 Apple 4,4,4,3 24 Lombardy poplar 14,12,11,11,10 25 Lombardy poplar 6,3 26 Lombardy poplar 16,15,14 28 Catalina cherry 9,6,6 31 Siberian elm Calif. black locust Monterey cypress 42

8 Updated Tree Report, July 2011 Page 6 Evaluation of Impacts The Tree Survey was the reference point for tree health and condition. I referred to the Preliminary Grading Plan prepared by Steven J. Lafranchi and Associates (dated 5/11/2011) to assess the impacts to trees from the proposed changes. The plan shows lot layouts, including proposed building locations, roads and drainage. Tree driplines and accurate trunk locations were shown on the plan, but utilities were not. The plan proposes to build 31 single-family residential units. A new walkway would connect Street B and the emergency vehicle access road with Corona Rd. to the north. A pedestrian and bicycle path is proposed along Corona Rd., adjacent to Lots 1 and 2. The existing house and surrounding trees on Lot 6 would remain. Eight (8) trees would be directly impacted by the proposed development, requiring their removal. The Lombardy poplars along Corona Rd. would be directly impacted by the proposed pedestrian/bicycle path, and five (5) trees would be impacted by Lot grading (#13, 15, 28, 31 and 33). The remaining 20 trees would be outside the development area and can be preserved, nine (9) of which were Protected. Preservation is predicated on following the Tree Preservation Guidelines provided at the end of this document. Table 3 provides a description of the proposed action (preserve or remove) as well as a description of the impacts. In summary, the current plan allows for the preservation of 20 trees, nine (9) of which were Protected. The remaining eight (8) trees are recommended for removal, seven (7) of which were of poor suitability for preservation and three (3) that qualified as Protected. Any pruning of the off-site tree must be done with the property owner s permission. Table 3: Recommendations for Action 470 and 498 Corona Rd., Petaluma CA Tree # Species Trunk Protected? Recommendation Diameter (in.) 1 Coast live oak 15 Yes Preserve; outside impacts. 2 Coast live oak 30,27 Yes Preserve; outside impacts. 3 Coast live oak 29 Yes Preserve; outside impacts. 4 Coast live oak 12 Yes Preserve; outside impacts. 5 Coast live oak 8,7 Yes Preserve; outside impacts. 6 Coast live oak 8,3 Yes Preserve; outside impacts. 7 Coast live oak 10,6 Yes Preserve; outside impacts. 8 Coast live oak 27 Yes Preserve; outside impacts. 10 Coast redwood 12 No Preserve; outside impacts. 11 Modesto ash 21 No Preserve; outside impacts. 12 Sweet gum 20 No Preserve; outside impacts. 13 Calif. black walnut 15,7 No Remove; impacted by Lot 8 grading. 15 Coast redwood 5 No Remove; impacted by Lot 5 grading. 16 English walnut 5,5,4,4,4 No Preserve; outside impacts. 18 English walnut 5,5,4,4 No Preserve; outside impacts. 19 English walnut 7,5,3 No Preserve; outside impacts. 20 Bradford pear 6,5,5,4 No Preserve; outside impacts. 21 Apple 4,4,4,3 No Preserve; outside impacts. 23 Coast live oak 15 Yes Preserve; outside impacts. (Continued, next page)

9 Updated Tree Report, July 2011 Page 7 Table 3: Recommendations for Action, continued 470 and 498 Corona Rd., Petaluma CA Tree # Species Trunk Protected? Recommendation Diameter (in.) 24 Lombardy poplar 14,12,11,11,10 Yes Remove; within pedestrian path. 25 Lombardy poplar 6,3 Yes Remove; within pedestrian path. 26 Lombardy poplar 16,15,14 Yes Remove; within pedestrian path. 28 Catalina cherry 9,6,6 No Remove; within Lot 1 grading. 29 Canary Island palm 28 No Preserve; 4' northeast of walkway. 30 Canary Island palm 31 No Preserve; 4' southwest of walkway. 31 Siberian elm 20 No Remove; within Lot 1 grading 33 Calif. black locust 26 No Remove; within Lot 1 grading 34 Monterey cypress 42 No Preserve; outside development impacts. Appraisal of Value The City of Petaluma requires that the value of all the Protected trees be established. To accomplish this, I used the standard methods found in Guide for Plant Appraisal, 9th edition (published in 2000 by the International Society of Arboriculture, Champaign IL). In addition, I 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 upon 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 North Bay area. The Species Classification and Group Assignment lists recommended species ratings and evaluations. Condition reflects the health and structural integrity of the individual, as noted in the Tree Survey Form. Location considers the site, placement and contribution of the tree in its surrounding landscape. The appraised value of the nine (9) Protected trees recommended for preservation is $37,950 (Table 4, following page). The appraised value of the three (3) Protected trees recommended for removal is $1,200 (Table 5, following page).

10 Updated Tree Report, July 2011 Page 8 Table 4: Appraised value of Protected trees to be preserved Tree No. Species Trunk Appraised diameter (in.) value ($) 1 Coast live oak 15 2,600 2 Coast live oak 30,27 14,250 3 Coast live oak 29 6,800 4 Coast live oak 12 1,650 5 Coast live oak 8,7 1,300 6 Coast live oak 8,3 1,050 7 Coast live oak 10,6 1,800 8 Coast live oak 27 5, Coast live oak 15 2,600 Total 37,950 Table 5: Appraised value of Protected trees to be removed Tree No. Species Trunk Appraised diameter (in.) value ($) 24 Lombardy poplar 14,12,11,11, Lombardy poplar 6, Lombardy poplar 16,15, Total 1,200 Mitigation Requirements The City of Petaluma requires mitigation for the approved removal of all Protected trees. Inkind mitigation is based on the condition of the tree. For Protected trees in good or excellent condition (rated a 4 or 5), mitigation is at a one to one trunk diameter basis; for Protected trees in fair or marginal condition (rated a 2 or 3), mitigation is at a two to one trunk diameter basis; and trees in poor condition (rated a 1) do not require mitigation. The City has defined a 24 box as equivalent to 2 of trunk diameter, a 36 box as equivalent to 3 of trunk diameter, and a 48 box as equivalent to 4 of trunk diameter. Lombardy poplars #24-26 were in marginal condition, and require mitigation at a two to one trunk diameter basis. Adding the sum of their trunk diameters and dividing by four (2 for marginal mitigation and 2 for inches per 24 box), resulted in a total of thirty (30) 24 box replacement trees that would be required. Based on the mitigation formula outlined above, a total of thirty (30) 24 box replacement trees would be required as mitigation for the approved removal of the three (3) Protected trees (Table 6, following page).

11 Updated Tree Report, July 2011 Page 9 Table 6. Mitigation calculation TREE SPECIES DIAMETER CONDITION Mitigation Required No. (in inches) 1=POOR Calculation Mitigation 5=EXCELLENT 24 Lombardy poplar 14,12,11,11, per 24 box 25 Lombardy poplar 6, per 24 box 26 Lombardy poplar 16,15, per 24 box Total Fifteen (15) 24 box trees Three (3) 24" box trees Twelve (12) 24" box trees 30 24" box trees 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 will depend on the amount of excavation and grading, the care with which demolition is undertaken, and the 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. 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. 2. A TREE PROTECTION ZONE shall be established around each tree to be preserved. For trees #1-8, 10-12, 16, 18-21, 23 and 34 the TPZ shall be established at the dripline. For tree #29 the TPZ shall be established at 4 to the northeast and at the dripline in all other directions and for tree #30, the TPZ shall be established at 4 to the southwest and at the dripline in all other directions. No grading, excavation, construction or storage of materials shall occur within that zone. 3. No underground services including utilities, sub-drains, water or sewer shall be placed in the TREE PROTECTION ZONE. 4. Tree Preservation Notes, prepared by the Consulting Arborist, should be included on all plans.

12 Updated Tree Report, July 2011 Page Any herbicides placed under paving materials must be safe for use around trees and labeled for that use. 6. Irrigation systems must be designed so that no trenching will occur within the TREE PROTECTION ZONE. Pre-construction treatments and recommendations 1. The construction superintendent shall meet with the Consulting Arborist before beginning work to discuss work procedures and tree protection. 2. Fence trees to be retained 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 Consulting Arborist. Fences are to remain until all grading and construction is completed. 3. Prune trees to be preserved to clean the crown and to provide clearance. Any pruning of off-site tree #34 must be done with the property owner s permission. All pruning shall be done by Certified Arborist or Certified Tree Worker in accordance with the Best Management Practices for Pruning (International Society of Arboriculture, 2002) and adhere to the most recent editions of the American National Standard for Tree Care Operations (Z133.1) and Pruning (A300). Recommendations for tree protection during construction 1. No grading, construction, demolition or other work shall occur within the TREE PROTECTION ZONE. Any modifications must be approved and monitored by the Consulting Arborist. 2. 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. 3. No excess soil, chemicals, debris, equipment or other materials shall be dumped or stored within the TREE PROTECTION ZONE. 4. Any additional tree pruning needed for clearance during construction or around new structures must be performed by a Certified Arborist and not by construction personnel. 5. 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.

13 Updated Tree Report, July 2011 Page 11 Maintenance of impacted trees Tree preserved at the Corona Road site will experience a physical environment different from that pre-development. 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 failure of branches or entire trees increases. Therefore, annual inspection for hazard potential is recommended. John Leffingwell Board Certified Master Arborist #WE3966B Registered Consulting Arborist #442 Attached: Tree Assessment Forms Tree Assessment Map