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HomeMy WebLinkAboutRS_Secondary_Arborist_Review_Forest_Terrace_200514.pdfFORESTRY AND VEGETATION MANAGEMENT SPECIALISTS WFCI 3601943-1 723 FAX 3601943-4 1 28 1919 Yelm Hwy SE, Suite C Olympia, WA 98501 URBANIRURAL FORESTRY TREE APPRAISAL HAZARD TREE ANALYSIS RIGHT-OF-WAYS VEGETATION MANAGEMENT ENVIRONMENTAL STUDIES CONTRACT FORESTERS Member of International Society of Arboriculture and Society of American Foresters May 12, 2020 Matthew Herrera – Senior Planner City of Renton Community & Economic Development 1055 S. Grady Way Renton, WA 98057-3232 RE: Forest Terrace Landscape Plan Review Dear Mr. Herrera: We have reviewed the landscape plans for the Forest Terrace residential subdivision at 2611 Union Ave. NE in Renton. The purpose was to determine if the proposed planting plans are compatible with the site and meet the requirements of the City of Renton tree protection ordinance. The scope of the evaluation was limited to: 1) Tract E – Tree Protection Area and 2) Tract E – Terraced Area. Findings and Recommendations The proposed plantings in the Tree Protection Area (TPA) and the Terraced Area (TA) were evaluated individually and will be treated separately. Tract E - Tree Protection Area: According to the Tree Solutions Arborist Report (dated November 19, 2019), about 94 of the 105 trees proposed for retention for this project are found in the Tract E - TPA, with sizes up to 46 inches diameter at breast height (DBH). There likely are many more trees in this stand that did not meet the threshold size for inventory and mapping. This stand appears to have a contiguous forest canopy (Attachment #1), meaning any new plantings will have to be shade tolerant. It is questionable as to the necessity for these proposed under plantings when the site is already occupied by trees and tree canopy. Only bigleaf maple and western hemlock of the species proposed for replanting are shade tolerant, and western hemlock is not a recommended species on these droughty soils. Western hemlock is considered to be off-site on these soils in the Puget Sound Region since it has been dying out of our natural stands for many years. Soils in this area are predominantly the Everett very gravelly sandy loam. The Everett very gravelly sandy loam is a very deep, somewhat excessively drained soil found on terraces and outwash plains. Seedling mortality is severe and new trees require irrigation to establish. Forest Terrace – Landscape Plan Review and Evaluation Washington Forestry Consultants, Inc. Page 2 No irrigation is proposed for the new under plantings in the Tract E - TPA. Given that proposed replacement trees are 3 inches caliper, mortality will likely be very high. Tract E - Terraced Landscape: The area between the Tract E - TPA and lots 14 – 24 includes up to 3 terraces with a 2:1 slope separated by 3.5 ft. high rockeries. Trees can be planted on these terraces, and with proper planting, mulching, irrigation, and follow-up maintenance trees can be successful. This north-facing slope is shaded by the canopies of retained trees in the Tract E - TPA. Shade intolerant or trees only intermediate in shade tolerance (i.e. Douglas-fir and Chinese dogwood) should not be used in these shady areas. Western redcedar, grand fir, vine maple, and Pacific dogwood are shade tolerant tree species that could be used, at least in the south half of the shaded slope. Douglas-fir and Chinese dogwood could be used as a replacement tree in the north half, where more sunlight will be available. The spacing of trees and landscape plants appears to be sufficient for adequate growth and development of proposed replacement trees. Tree Size: The landscape plans specifies that 3 inch caliper replacement trees are to be used. Large caliper trees such as these typically establish slower with higher mortality rates than smaller trees. Therefore, WFCI recommends limiting the maximum size of trees to be planted for this project to 6-7 ft. tall if coniferous and 2 inches in caliper if deciduous. This will reduce transplant shock, improve survival and early growth, and will result in better establishment rates and larger, healthier trees 5 years after planting. If this results in the planting plan falling short of the required tree replacement, then a fee-in-lieu paid to the City of Renton can compensate for the shortfall. In our opinion, this would be preferable to an expensive, unsuccessful planting. The following Figure 1 below illustrates the fact that transplanting smaller trees results in faster growth and better establishment rates than transplanting larger trees. The solid circle on the stem illustrates the diameter of the tree at planting. The tree on the left was smaller at planting time, but established and began growth early, more than doubling the size of the tree on the right after 5 years. Forest Terrace – Landscape Plan Review and Evaluation Washington Forestry Consultants, Inc. Page 3 Figure 1. Cross-section of 2 spruce (Picea spp.) stems 5 years after transplanting showing effect of increased transplant stress larger-caliper trees (The Morton Arboretum, Lisle, Ill.). In Pacific Northwest forestry operations, we find the same is true of large seedlings or transplant stock versus smaller sized seedlings or transplant stock – typically the smaller sized trees will catch up to and outgrow the larger sized trees. The better the root-shoot balance, the better the survival and early growth. Summary The following is a summary of our review: 1. The Tract E - Tree Protection Area appears to be fully stocked with existing trees. Planting new trees in the understory of this forest stand with no irrigation provided does not appear useful and is not recommended. If trees are to be under planted, then they must be irrigated. 2. The Tract E – Terraced Area as designed can support the proposed new tree and shrub plantings, and the irrigation plan appears adequate to water the trees. 3. Trees planted in the shade of the overstory trees in the Tract E – Tree Protection Area need to be shade tolerant species. Even trees planted on the north-facing slope of the Tract E – Terraced Area must be shade tolerant in at least the south half of the area. Western hemlock is not suitable for use on this site. 4. Proposed tree size: Planting 3 inch caliper trees will reduce the survival and short-term growth of the planted trees on the Tract E – Terraced Area. Planting smaller trees such as 6-7 ft. tall conifers and 2 inch caliper deciduous will greatly improve early survival, establishment and growth. 5. Reduction of tree size for replacement will cause the project to fall under the caliper inches of tree replacement requirement – payment into the tree fund may be a better plan. 6. The irrigation where provided appears adequate to support tree survival and growth. Forest Terrace – Landscape Plan Review and Evaluation Washington Forestry Consultants, Inc. Page 4 Please give us a call if you have any questions. Respectfully submitted, Washington Forestry Consultants, Inc. Galen M. Wright, ACF, AS Riley Stark, Professional Forester ISA Bd. Certified Master Arborist PN-129BU ISA Bd. Certified Master Arborist Certified Forester No. 44 Municipal Specialist, PN-7780BM ISA Tree Risk Assessor Qualified ISA Tree Risk Assessor Qualified ASCA Tree and Plant Appraisal Qualified Forest Terrace – Landscape Plan Review and Evaluation Washington Forestry Consultants, Inc. Page 5 Attachment #1. Aerial Photo of Forest Terrace Project Area (2019 King County iMap) Project Area Boundary N Forest Terrace – Landscape Plan Review and Evaluation Washington Forestry Consultants, Inc. Page 6 Attachment #2. Planting and Irrigation Plans Reviewed (4 pages attached) Forest Terrace – Landscape Plan Review and Evaluation Washington Forestry Consultants, Inc. Page 7 Attachment #3. Assumptions and Limiting Conditions Washington Forestry Consultants, Inc. 1) Any legal description provided to the Washington Forestry Consultants, Inc. is assumed to be correct. Any titles and ownership's to any property are assumed to be good and marketable. No responsibility is assumed for matters legal in character. Any and all property is appraised or evaluated as though free and clear, under responsible ownership and competent management. 2) It is assumed that any property is not in violation of any applicable codes, ordinances, statutes, or other governmental regulations, unless otherwise stated. 3) Care has been taken to obtain all information from reliable sources. All data has been verified insofar as possible; however, Washington Forestry Consultants, Inc. can neither guarantee nor be responsible for the accuracy of information. 4) Washington Forestry Consultants, Inc. shall not be required to give testimony or to attend court by reason of 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. 5) Loss or alteration of any part of this report invalidated the entire report. 6) 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 expressed written or verbal consent of Washington Forestry Consultants, Inc.. 7) Neither all or any part of the contents of this report, nor copy thereof, shall be conveyed by anyone, including the client, to the public through advertising, public relations, news, sales or other media, without the prior expressed written or verbal consent of Washington Forestry Consultants, Inc. -- particularly as to value conclusions, identity of Washington Forestry Consultants, Inc., or any reference to any professional society or to any initialed designation conferred upon Washington Forestry Consultants, Inc. as stated in its qualifications. 8) This report and any values expressed herein represent the opinion of Washington Forestry Consultants, Inc., and the fee is in no way contingent upon the reporting of a specified value, a stipulated result, the occurrence neither of a subsequent event, nor upon any finding in to reported. 9) Sketches, diagrams, graphs, and photographs in this report, being intended as visual aids, are not necessarily to scale and should not be construed as engineering or architectural reports or surveys. 10) Unless expressed otherwise: 1) information contained in this report covers only those items that were examined and reflects the condition of those items at the time of inspection; and 2) the inspection is limited to visual examination of accessible items without dissection, excavation, probing, or coring. There is no warranty or guarantee, expressed or implied, that problems or deficiencies of the tree or other plant or property in question may not arise in the future.