Loading...
2020-035 Tree Protection During ConstructionDate: April 10, 2020 Report No. 2020-035       INFORMAL STAFF REPORT TO MAYOR AND CITY COUNCIL SUBJECT: Tree Protection during construction. BACKGROUND: In January, staff received a request to develop a comprehensive tree protection protocol for internal and external development/redevelopment projects as it relates to construction. Parks and Recreation staff coordinated with Engineering to develop criteria that are consistent with the industry best management practices (BMPs) produced by Texas A&M Forest Service, and rooted in the American National Standards Institute (ANSI) A300 Part 5: "Trees, Shrubs, and other Woody Plant Maintenance – Standard Practices (Management of Trees and Shrubs During Site Development, and Construction)." DISCUSSION: The guide provides BMPs for protecting trees to be preserved during the replacement, repair, and construction of infrastructure in the City of Denton. The intent is to cover the majority of tree protection scenarios. However, there may be site-specific circumstances that require a custom solution to working around the tree to be preserved. The guide covers general tree protection but focuses on protecting trees while constructing/reconstructing or repairing streets, curbs, sidewalks, and underground utilities. While developing the process, staff took into consideration the protection of trees on public right-of-ways as well as private property. CONCLUSION: The guide will be distributed to internal and external crews that construct/reconstruct public infrastructure projects for the City of Denton. Once in use, it will reduce construction-related damage to trees above and below the ground. STAFF CONTACT: Haywood Morgan Urban Forester, Parks and Recreation Haywood.Morgan@cityofdenton.com REQUESTOR: City Council PARTICIPATING DEPARTMENTS: Parks and Recreation Engineering STAFF TIME TO COMPLETE REPORT: Parks and Recreation 12 hours Engineering 3 hours Total 15 hours City of Denton Tree Protection During Construction This guide is to provide Best Management Practices (BMPs) for protecting trees to be preserved during the replacement, repair, & construction of infrastructure in the City of Denton. The following requirements are based on ANSI A300 Part 5: Trees, Shrubs, and other Woody Plant Maintenance – Standard Practices (Management of Trees and Shrubs During Site Development, and Construction). The intent is to cover the majority of tree protection scenarios, however there may be site specific circumstances that require a custom solution to working around the tree to be preserved. Definitions Critical Root Zone (CRZ) is the area of soil extending from the tree trunk where roots required for future tree health and survival are located. This area can also be defined as a circle with a minimum radius of 1’ for every 1” in trunk diameter at 4.5” above ground. Tree protection barrier encloses the Tree Protection Zone and is at least 4’ tall, highly visible, sturdy, permanent and has warning signs on or near it for the duration of any construction activities. Trunk protection consist of 2-inch thick wooden planks such as 2x4’s installed around the tree with a closed-cell foam pad secured with straps or wire to hold the planks in place. Tree Protection Zone (TPZ) is an area where construction activities are prohibited or restricted to prevent injury to preserved trees, especially during pre-construction and construction, and includes the Critical Root Zone and/or beyond. For the City of Denton purposes the TPZ will be equal to the CRZ. 4” tall or greater, Highly visible, sturdy, and permanent Tree Protection Barrier Highly Visible Warning Sign Streets and Curbs Existing street and curb reconstruction or repair – When reconstructing or repairing existing streets the CRZ of trees located within the tree lawn are to be protected with a tree protection barrier in all pervious areas of the R.O.W. For trees behind the sidewalk including private trees that have CRZ that extend into the right of way (R.O.W.). The CRZ is to be protected with a tree protection barrier in all pervious areas of the R.O.W. Tree protection is not to extend on private property. Construction of new streets and sidewalk – When constructing new streets the CRZ of all trees identified to be preserved are to be protected with a tree protection barrier. In an effort to preserve more trees, encroachment into the CRZ on the street side of the tree is allowed up to ½ the distance to the trunk. All expose roots are to be pruned back to the soil level. Sidewalks and Curbs Existing sidewalk reconstruction or repair – When reconstructing or repairing existing sidewalks, the trunks of trees located within the tree lawns are to have trunk protection. Any private tree within 5 feet of the sidewalk is to have a tree protection barrier parallel to the sidewalk in the R.O.W for the length of the CRZ. Tree protection is not to extend on private property. Under no circumstance should heavy equipment be driven on the CRZ before or after the sidewalk has been removed. Do not pile/store anything in the CRZ of the protected trees including but not limited to soil, gravel, concrete, tool and equipment. When replacing sidewalk next to existing trees it may be necessary to allow more space for future growth of the tree by: 1) shifting the sidewalk to the furthest extent of the R.O.W. away from the tree, 2) reducing the width of the sidewalk adjacent to the tree, 3) acquiring additional R.O.W. to shift the sidewalk away from the tree, 4) pruning or ramping over the offending root before pouring new sidewalk or 5) a combination of the above. Construction of new sidewalks in existing neighborhood – When constructing new sidewalks, the trunks of trees located within the tree lawns are to have trunk protection. Any private tree within 5 feet of the side walk is to have a tree protection barrier parallel to the sidewalk in the R.O.W for the length of the CRZ. Tree protection is not to extend on private property. Under no circumstance should heavy equipment be driven on the CRZ before or after the sidewalk has been removed. Do not pile/store anything in the CRZ of the protected trees including but not limited to soil, gravel, concrete, tool and equipment. The following methods of excavation is the CRZ are acceptable: 1) air spade, 2) hand digging or hydro-excavator. The air space is preferable. Expose roots less than 2 inches may be pruned back to edge of the sidewalk forms as needed. When constructing new sidewalk next to exiting trees it may be necessary to allow more space for future growth of the tree by: 1) shifting the sidewalk to the furthest extent of the R.O.W. away from the tree, 2) reducing the width of the side walk adjacent to the tree, 3) acquiring additional R.O.W. to shift the sidewalk away from the tree or 4) pruning or ramping over the offending root before pouring new sidewalk or 5) a combination of the above. Curbs Existing curb reconstruction or repair – When reconstructing or repairing existing curbs, the CRZ of trees located within the tree lawn are to be protected with a tree protection barrier in all pervious areas of the R.O.W. For trees behind the sidewalk including private trees that have CRZ that extend into the R.O.W. the CRZ is to be protected in all pervious areas of the R.O.W. Tree protection is not to extend on private property. Any excavation next to tree is to be done by 1) Air spade, 2) hand digging or hydro-excavator. Underground Utilities Underground utilities installation or repair – When installing underground utilities within the CRZ install by boring, if excavation is necessary in the CRZ, the following methods are acceptable: 1) air spade, 2) hand digging or hydro- excavator. The air space is preferable. The trunks of trees located within the tree lawns are to have trunk protection. Any private tree within 5 feet of the side walk is to have a tree protection barrier parallel to the R.O.W or easement for the length of the CRZ. Tree protection is not to extend on private property. Under no circumstance should heavy equipment be driven on the CRZ before or after the sidewalk has been removed. Do not pile/store anything in the CRZ of the protected trees including but not limited to soil, gravel, concrete, tool and equipment.