Loading...
HomeMy WebLinkAboutUntitled Oak Tree Protection Report for Dripline Encroachment 1402, 1406, 1410 S. 8th Avenue Arcadia, CA 91006 Prepared for: Dexter 8th Avenue, LLC. Tel: (626) 215-7685 Fax: (626) 574-6408 Prepared by: Michael Crane ASCA Registered Consulting Arborist #440 ISA Board Certified Master Arborist #WE-6643B California Agricultural Pest Control Adviser #08269 Tel./Fax. (626) 737-4007 ;; .'- Ci4k0 April, 2009 /4.10° ,�� 1 \t ' ' r� \ ./ \151W ►�ta� �nsu�/ II Table of Contents Summary 1 II Background and Purpose 1 Observations& Analysis 1 Discussion 3 Size and Distribution of Tree Roots 3 Root Pruning 4 Conclusions & Recommendations 5 Details of Protection Measures 5 Design Modifications 6 II Photos 7 Certification of Performance 8 Site Map Back Pocket II Oak Tree Enroachment&Protection Report 1402,1406,1410 S.8th Ave.,Arcadia,91006 April,2009 SUMMARY Although no above-ground portion of the oak tree will be pruned or removed in order to accomplish the construction plans, there will be significant encroachment into the rootzone on one side. The encroachments include the construction of a road with a curb, gutter and sidewalk as well as a boundary line block wall. The sidewalk should be bridged with a section of interlocking paver stones on uncompacted sand. A section of the block wall should be designed with a break in the footing that is connected with a wrought iron fence built on posts. These modifications will significantly reduce the structural damage to buttress roots and future hazard risk of a whole tree failure. The most significant health risk to the tree is the potential for excessive soil compaction. This risk can be successfully avoided by establishing a protected zone and performing all excavations within the zone by hand tools or air spade. Recommended mitigation for the encroachment is the installation of one 60" boxed nursery grown Coast Live Oak on the subject property. Details of the preservation plan are given in this report. BACKGROUND & PURPOSE The property at 1410 S. 8th Avenue is planned to be redeveloped. The existing home will be demolished and a flag lot will be developed with five home sites. There is a protected oak tree located on the south property line. The dripline of the oak will be encroached during the proposed construction. I was retained by the property owner and developer, Mr. Charles Huang, as the project's consulting arborist. My first assignment was to write a tree protection report for the dripline encroachments which are expected to occur. The report is intended to be used both to provide the necessary information to the Arcadia Planning Department for their design review and to assist the building contractor with the necessary measures for proper tree protection. I made my site visit on April 27, 2009. OBSERVATIONS & ANALYSIS There is one Coast Live Oak, Quercus agrifolia, located in the existiting back yard area of the property. The tree has a trunk diameter measuring 28 inches at four and a half feet above grade. It has an approximate height of 45 feet and an average spread of 35 feet. The tree has been plotted on the site plan which is included in this report and the dripline has been accurately drawn and highlighted. The tree appears to be in good health and condition. There are no signs of disease or other heath problems and it has never been improperly pruned. The canopy is symmetrical and its structure is good. Photos of the tree and site are located on page 7. The construction plans will require no pruning of any above-ground portion of the tree i but will involve root disruption from excavation and compaction within the dripline. The �0�� most significant encroachment will be the construction of a new road with curb, gutter and sidewalk (see Detail A on next page). The required excavation for the curb will come as close as four feet from the trunk when considering the overexcavation that may T-1 E be necessary. The other encroachment will be for the construction of a new boundary FPC 0 F line wall located on the edge of the sidewalk closest to the tree. C1,1Q THE 13Ac.K 4r- C��n-g Wouu1 rte 1 TO E. A1/4C-cuFL pec.. .,p _rI0►--1 4 Q _ � PT Vlot-i COULD Oak Tree Enroachment&Protection Report 1402,1406,1410 S.8th Ave.,Arcadia,91006 April,2009 CURB & A.GUI7ER 2' EX. 30" OAK TO BE PROTECTED • DETAIL "A" SACLE: 1"=10' The detail above shows the road, curb, gutter and sidewalk. A boundary line wall will be built on the edge of the sidewalk closest to the tree. Both the sidewalk and wall will be contoured around the tree to accommodate the trunk. Modifications to this design will be for a section of the sidewalk to be constructed with interlocking pavers on uncompacted sand and the block wall to be interrupted with a section of wrought iron fence built with iron posts. Details of these modifications are located in the Recommendations — Design Modifications section located on page 6. 2 I Oak Tree Enroachment&Protection Report 1402,1406, 1410 S.8th Ave.,Arcadia,91006 April,2009 DISCUSSION Size and Distribution of Tree Roots— Taken from Arboriculture, Integrated Management of Landscape Trees Shrubs and Vines. Harris, R.W., Clark, J.W., Matheny N.P. Prentice Hall 2004. GU R-f5 Roots of most plants, including large trees, grow primarily in the top meter (3 ft) of soil C&a i (see figure below). Most plants concentrate the majority of their small absorbing roots in WOULD the upper 150 mm (6 in.) of soil if the surface is protected by a mulch or forest litter. In Cio DOWI- the absence of a protective mulch, exposed bare soil can become so hot near the surface '`o kecuf that roots do not grow in the upper 200 to 250 mm (8 to 10 in.). Under forest and many 214'fir' landscape situations, however, soil near the surface is most favorable for root growth. In -T3 addition, roots tend to grow at about the same soil depth regardless of the slope of the soil E)(CP/I`""E surface. Although root growth is greatly influenced by soil conditions, individual roots seem to have an inherent guidance mechanism. Large roots with vigorous tips usually grow horizontally. Similar roots lateral to the large roots grow at many angles to the vertical, and some grow up into the surface soil. However, few roots in a root system actually grow down. . 444 . - Depth Inn Depth in motors a 1A 6 s 1.5 PtGURE In mature trees,the taproot is either lost or reduced in size.The vast majority of the root system is composed of horizontally oriented lateral roots. 3 Oak Tree Enroachment&Protection Report 1402,1406, 1410 S.8th Ave.,Arcadia,91006 April,2009 Root Pruning-Taken from Root Pruning. Hagen, Bruce W. International Society of Arboriculture Western Arborist V. 33 #2 pp. 18-22 Decisions regarding the minimum distance from the trunk and the extent of root removal should be based on the potential impacts of both tree health and root stability. Tree roots are concentrated near the soil surface, and even minor digging can cause significant damage to tree root systems unless adequate precautions are taken. Root cutting, depending on severity, can cause dieback or decline by restricting water and nutrient uptake. Loss of roots close to the trunk can also have an immediate destabilizing effect and can ultimately lead to severe root decay. There are no well-defined standards regarding the percentage of root mass that can be cut without appreciably affecting tree health because there are so many variables involved. It's not uncommon, though, for trees to survive after losing more than 50 percent of their root systems. The number, size of roots cut, and distance from the trunk are more �� 2y`: important than the percentage of roots cut. The loss of roots on one side of a tree at about five times the trunk diameter is generally considered to be acceptable, depending on tree 10 health, condition and root distribution. 1 <- Some guidelines for avoiding or minimizing impacts to tree health and stability include: • Roots within three times the trunk diameter(dbh) are critical to a tree's stability > )4•1-‘-1 and should not be cut. Major buttress roots cut within this distance should be considered as providing little or no structural support. Rao ti • Avoid cutting buttress roots on the windward side of trees, particularly large Sb N'(p, buttress roots that have developed in response to continual windloading. N 11 lQ` Cotolt flzoim • When roots must be cut, do so in a manner that prevents ripping, splitting or IyOttervi- SKI tearing. Cuts should be made using a sharp hand tool, such as a saw or pruners, to TN C tat' ensure a clean cut. This will encourage callous tissue formation and root GSF 0 T regeneration. Wound dressings are generally not recommended. twi 461 E • Cover all hand cut, exposed roots with moistened burlap, black plastic tarping, etc. or fill soil to avoid desiccation. 4 I Oak Tree Enroachment&Protection Report 1402,1406,1410 S.8th Ave.,Arcadia,91006 April,2009 CONCLUSION & RECOMMENDATIONS The planned construction can be accomplished without causing stability problems with the tree if both the sidewalk and the boundary line wall are modified in design. Furthermore, extreme care must be taken throughout the project, especially during excavation to minimize the future health of the tree. Significant root pruning will likely occur as well as soil compaction for the construction of the road. This devastating impact can be successfully minimized by proper planning and establishment of a root protection zone. Details of Protection Measures: • Install a six foot tall chain link fence as indicated on the site plan. The fence is to be installed no closer than 15 feet from the trunk. This fence is to be installed before demolition and shall be maintained throughout the duration of the project. The fence will be a six foot tall chain link type secured with metal posts and a small opening should be left on one side to provide entry by the arborist. The location for the protective fence is drawn in red on the site plan. • All activity within the fenced protective zone shall be approved and monitored by the arborist. • All excavation within the fenced protected zone shall be accomplished with hand tools and initial excavation is to be done with an air knife. The air knife is a pneumatic device that uses compressed air to excavate soil while preserving roots. It is useful in identifying the locations of significant roots so that proper root pruning is accomplished. • No washing out ore storage of any construction related materials is permitted within the fenced protected zone. • No mounding of soil or any other unpermitted grade changes shall occur within the fenced protected zone. • All utilities, including new landscape irrigation, shall be routed as far from the trunk of as possible. When utilities must be routed through the dripline the trenches shall be hand excavated and all roots one inch or larger shall be preserved and utility lines tunneled underneath. • Irrigation schedules, fertilizer and pesticide recommendations shall be prescribed by the consulting arborist through regular monitoring during the project. 5 0 Oak Tree Enroachment&Protection Report 1402,1406,1410 S.8th Ave.,Arcadia,91006 April,2009 Design Modifications: WILCO u4wr .Oru FEsC,E SEGTto� , AMER lill 30' 5EcTloN of SIO ' 50'c.T "i rww rAveg,sTb1465 o,4) %NCor,PPc-rte sAmjs A 30' long section of the sidewalk on center with the trunk should be constructed with interlocking pavers on uncompacted sand. The block wall with a continuous footing should be interrupted with a 15' long section of wrought iron fence built with iron posts. This fence section should be on center with the trunk and contoured around the trunk which is 10 located on the property line. All excavation should be done with an air knife and hand tools and monitored by the arborist. 6 Oak Tree Enroachment&Protection Report 1402,1406,1410 S.8th Ave.,Arcadia,91006 April,2009 PHOTOS . 4• a Photo 1: Subject oak tree taken facing south. t ; 1 �' Ni• k x, ,f t '40,/Pi .:' .)94111. r . .ip, ! .. If 1111 -44011110"16.....,awiaar Photo 2: Subject oak tree(circled)as viewed facing east from S. 8th Ave. 7 I Oak Tree Enroachment&Protection Report 1402,1406,1410 S.8th Ave.,Arcadia,91006 April,2009 CERTIFICATION OF PERFORMANCE I, Michael Crane, certify that: • I have personally inspected the tree(s) and the property referred to in this report and have stated my findings accurately. • I have no current or prospective interest in the vegetation or the property that is 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 not 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 in good standing of the American Society of Consulting Arborists and the International Society of Arboriculture. I have been involved in the field of Horticulture in a full-time capacity for a period of more than 15 years. Signed: Registered Consulting Arborist#440; American Society of Consulting Arborist Board Certified Master Arborist #WE 6643B; International Society of Arboriculture Licensed California Agricultural Pest Control Adviser#AA08269 8