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HomeMy WebLinkAbout9. TreeRetentionWorksheetDEPARTMENT OF COMMUNITY AND ECONOMIC DEVELOPMENT 1 U:\PSO\Projects\Clients\1521-KingCo\554-1521-084 L2ST\02WBS\PH-A 2 Rivers\Shoreline CUP\TreeRetentionWorksheet.docx 03/2015 TREE RETENTION WORKSHEET Planning Division 1055 South Grady Way-Renton, WA 98057 Phone: 425-430-7200 Fax: 425-430-7231 1. Total number of trees over 6” diameter1, or alder or cottonwood trees at least 8” in diameter on project site 16,000 trees 2. Deductions: Certain trees are excluded from the retention calculation: Trees that are dangerous2 0 trees Trees in proposed public streets 0 trees Trees in proposed private access easements/tracts 0 trees Trees in critical areas3 and buffers 8,000 trees Total number of excluded trees: 8,000 trees 3. Subtract line 2 from line 1: 8,000 trees 4. Next, to determine the number of trees that must be retained4, multiply line 3 by: 0.3 in zones RC, R-1, R-4, R-6 or R-8 0.2 in all other residential zones 0.1 in all commercial and industrial zones 2,400 trees 5. List the number of 6” in diameter, or alder or cottonwood trees over 8” in diameter that you are proposing5 to retain4: 7,869 trees 6. Subtract line 5 from line 4 for trees to be replaced: (if line 6 is zero or less, stop here. No replacement trees are required) 0 trees 7. Multiply line 6 by 12” for number of required replacement inches: 0 inches 8. Proposed size of trees to meet additional planting requirement: (Minimum 2” caliper trees required) 0 inches per tree 9. Divide line 7 by line 8 for number of replacement trees6: (If remainder is .5 or greater, round up to the next whole number) 0 trees 1 Measured at 4.5’ above grade. 2 A tree certified, in a written report, as dead, terminally diseased, damaged, or otherwise dangerous to persons or property by a licensed landscape architect, or certified arborist, and approved by the City. 3 Critical areas, such as wetlands, streams, floodplains and protected slopes, are defined in RMC 4-3-050. 4 Count only those trees to be retained outside of critical areas and buffers. 5 The City may require modification of the tree retention plan to ensure retention of the maximum number of trees per RMC 4-4-130H7a. 6 When the required number of protected trees cannot be retained, replacement trees, with at least a two-inch (2") caliper or an evergreen at least six feet (6') tall, shall be planted. See RMC 4-4-130.H.1.e.(ii) for prohibited types of replacement trees. 2 U:\PSO\Projects\Clients\1521-KingCo\554-1521-084 L2ST\02WBS\PH-A 2 Rivers\Shoreline CUP\TreeRetentionWorksheet.docx 03/2015 Minimum Tree Density A minimum tree density shall be maintained on each residentially zoned lot (exempting single-family dwellings in R-10 and R-14). The tree density may consist of existing trees, replacement trees, or a combination. Detached single-family development7: Two (2) significant trees8 for every five thousand (5,000) sq. ft. of lot area. For example, a lot with 9,600 square feet and a detached single-family house is required to have four (4) significant trees or their equivalent in caliper inches (one or more trees with a combined diameter of 24”). This is determined with the following formula: Multi-family development (attached dwellings): Four (4) significant trees8 for every five thousand (5,000) sq. ft. of lot area. Example Tree Density Table: Lot Lot size Min significant trees required New Trees Retained Trees Compliant 1 5,000 2 2 @ 2” caliper 0 Yes 2 10,000 4 0 1 tree (24 caliper inches) Yes 3 15,000 6 2 @ 2” caliper 1 Maple – 15 caliper inches 1 Fir – 9 caliper inches. Yes 7 Lots developed with detached dwellings in the R-10 and R-14 zoned are exempt from maintaining a minimum number of significant trees onsite, however they are not exempt from the annual tree removal limits. 8 Or the gross equivalent of caliper inches provided by one (1) or more trees. Lake to Sound Trail Segment A Renton Permits NOTES ON TREE RETENTION WORKSHEET 1. Total number of trees The site traverses a site of about 80 acres. We did not do a tree survey over the entire site We estimate 200 trees per acre, based on the tree density in a mature Pacific Northwest Forest from the following publications: Hardwoods of the Pacific Northwest, S.S. Niemiec, G.R. Ahrens, S. Willits, and D.E. Hibbs. 1995. Research Contribution 8. Oregon State University, Forest Research Laboratory http://owic.oregonstate.edu/red-alder-alnus-rubra Yield tables for managed stands of coast Douglas-fir Curtis, Robert 0.; Clendenen, Gary W.; Reukema, Donald L.; DeMars, Donald J. 1982. Yield tables for managed stands of coast Douglas- fir. Gen. Tech. Rep. PNW-GTR-135. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Forest and Range Experiment Station. 182 p. http://www.fs.fed.us/pnw/publications/pnw_gtr135/pnw_gtr135a.pdf Portions of the site have been cleared with limited tree cover, however this estimate is likely to be relatively accurate. 2. The deduction for 60 Critical Areas includes both wetlands and buffers. Wetlands have not been fully delineated, so this is a rough estimate. It is intended to be conservative. If wetlands and buffers are a greater percent of the sit, the number of trees required to be retained would be lower. 4. Trees that must be retained: The estimate of 2,400 was based on the maximum multiplier of .3. This is the tree count for the entire site outside Critical Areas, not just the portion within or near the trail corridor. 5. Trees proposed to be retained are all trees, minus 151 designated for removal = 7849 which is 98 percent of the trees on the non-critical portion of the site. 9. Tree replacement is proposed for all trees removed.