1993 Specifications CSJ'S & SPECIAL SPECIFICATION ITEM Tree Preservation and Treatment

Transcription

1 1993 Specifications CSJ'S & SPECIAL SPECIFICATION ITEM 1016 Tree Preservation and Treatment 1. Description. This section specifies the requirements for protecting trees and related services including: trimming, fertilization, root prune trenching, vapor barrier installation, watering, chemical treatment and other tree preservation techniques as indicated on drawings and described herein. 2. Quality Assurance. All tree trimming, fertilizing, chemical treatment and work involving tree roots required to protect trees shall be performed by or under the supervision of a qualified Arborist or Urban Forester. 3. Job Conditions. a. Contractor shall not allow any vehicular traffic, construction equipment, parking of vehicles or stockpiling of excavated material or construction materials within tree protection fences. b. Trees to be preserved shall be watered to maintain their healthy growth and to ensure they do not become moisture stressed during the course of construction operations. 4. Definitions. a. Dripline. The dripline of a tree is defined as the outer tips or ends of the limbs and the soil below which contains tree roots. b. Root Zone Area. The root zone area of the tree is defined as the ground area extending out from the tree trunk to the end of the limb tips or dripline. This area is considered to be the most critical area of roots and should be protected. c. Zero Curb Cut. Zero curb cut - no soil disturbance back of curb. The process in which required work is conducted without cutting or otherwise disturbing soil located behind the existing curb

2 5. Materials. a. Tree Protection Fencing. Orange, plastic mesh fencing, 4 feet in height with 6 feet high t -bar posts installed as per drawings. Set posts 1.5 feet into ground. Stretch fencing material tight prior to securing. b. Plastic Vapor Barrier. 6 mil. polyethylene plastic sheeting (on rolls) min. 3 foot width. c. Fertilizer. Arbor-Green, mixed and applied per label instructions. the nitrogen per 1,000 sq. ft. will be as shown in the plans. 6. Construction Methods. a. General. Contractor and all sub-contractors shall attend a preconstruction meeting given by the Engineer and Project Forester to review tree preservation requirements and sequence of services for the construction process. b. Protection. 1. Protect tree root systems from damage due to noxious materials in solution caused by run-off or spillage during mixing and placement of construction materials, or drainage from stored materials. 2. Protect tree limbs, trunks and foliage from direct exposure to hot exhaust from equipment by providing adequate exhaust pipe deflectors. 3. Protect exposed roots and root zone areas from contamination from stabilization materials and concrete by placing a sheet of 6 mil poly over horizontal or vertical grade prior to pouring concrete curbs, inlets, driveways and ramps within root zone. 4. Designate limited areas as concrete washout areas. Locate concrete washout areas away from root zones. 5. Cover exposed roots within 24 hours to reduce damage caused by desiccation. Roots may be covered with soil, mulch, or wet burlap to help protect them from drying. 6. Site preparation work and/or construction work shall not begin in any area where tree preservation measures have not been completed and approved. c. Preparation. 1. Fencing operations will necessitate access areas for workers, materials and equipment. 2. Contractor shall not allow any vehicular traffic, parking of

3 vehicles or stockpiling of excavated material or construction material within the dripline of trees to be preserved. 3. Should access be necessary within root zone areas, place a 3/4" thick plywood driving surface over the existing grade to help distribute the weight of equipment and minimize soil compaction and rutting. This is not acceptable bridging for driving over exposed tree roots. Exposed roots should not be driven over. 4. Contractor shall notify Engineer if existing tree locations differ from locations represented on drawings. The dripline as observed in the field shall superceed that outlined on construction plans. d. Root Pruning and Vapor Barrier Installation. 1. Root pruning trenching and vapor barrier installation (if apllicable) locations are designated on the tree preservation plan. Exact locations shall be approved in the field by the Engineer or Project Forester. Trenching depth and vapor barrier shall extend 10 inches below proposed soil stabilization limits. After installation of vapor barrier, trench shall be backfilled with loose soil and compacted. e. Tree Protection Fences. 1. Each tree to be preserved shall be protected with a tree protection fence. The fencing shall be continuous between posts, shall be pulled taut prior to securing to posts, and shall be firmly attached to the posts with a minimum of 4 wire ties. 2. The fence shall be placed in a continuous alignment around a tree or group of trees designated to be preserved as shown on the preservation plan. Fences shall be placed to protect roots, trunks and foliage and generally shall be placed 5 feet outside the dripline of a tree or group of trees being protected, however the fence shall be located two feet from the back of curb. The location of a fence may be inside the above-stated limit in a situation where requirements of the work require operations inside the limit, as shown on the drawings or with the approval of the Project Forester prior to placing the fence. The Contractor shall not remove or relocate tree protection fencing and shall not operate within the limits shown without direct approval of the Project Forester. 3. Storage of equipment or materials will not be allowed inside a fence. Entryways into a protected area shall not be provided unless approved by the Project Forester. 4. Damage to tree fences occurring during the progress of the work shall be repaired immediately at no additional cost to owner. Workmen shall be clearly instructed to exercise caution in performance of work near trees being preserved

4 f. Pruning. 1. Where canopy of tree extends over the street, prune for clearance of normal vehicle traffic only. Prune to clear street feet. Extent of pruning shall be based upon requirements to clear limbs to a maximum height of feet over the street. Additional clearance pruning for construction activity access will not be allowed. All pruning shall be approved by the Project Forester before beginning. 2. Contractor shall notify property owner prior to trimming or pruning any trees on private property. 3. Trees shall be pruned in a manner that will not destroy or alter the natural shape and character of the tree. Apply appropriate, non-toxic wound paint to all fresh wounds on oak trees after pruning. 4. All cuts should be made sufficiently close to the parent limb or trunk without cutting into the branch collar or leaving a protruding stub, so that closure can readily start under normal conditions. Clean cuts should be made at all times. g. Fertilizer 1. Deep root fertilize designated trees. Fertilization application dates shall be determined by the Project Forester. 2. Fertilize entire root zone area within the dripline of the tree and continue 10 feet beyond the dripline. 3. Fertilizer shall be Arbor-Green, , or approved substitute. 4. Mixture shall be injected into the top 10 inches of soil under pressure of psi. 5. Application of nitrogen per 1,000 square feet will be as shown in the plans. Inject to a depth of 10 inches and a spacing of 3 feet between injection points. 6. Fertilizer shall be mixed in a tank with mechanical agitation capability. h. Watering. 1. Trees which have received root damage should be watered regularly to eliminate additional stress caused by lack of moisture. Water during periods without adequate rainfall. For example, should 1.5" of rain not be received within a week period, the trees should be thoroughly watered. March through September, water once every two weeks. October through February, water every three weeks. Water thoroughly to saturate the entire root zone area

5 2. Foliage, limbs and trunks shall be rinsed with fresh water to remove dust accumulated during the demolition and construction process as necessary. Frequency shall be determined by the forester. i. Chemical Treatment. Treat tree trunks with evidence of borer activity with the appropriate approved insecticide mixed and applied per the manufacturer's product application recommendations. Trees shall be sprayed within 24 hours after observance of borer activity. j. Excavation Around Trees. 1. Excavate within the dripline of trees only where indicated. where trenching for construction of utilities is required within the dripline, tunnel under the root zone using the tunnel boring method at a minimum depth of over 4 feet. Bore pits and peep holes shall be located outside of root zone areas. 2. Where excavating is required within root zones at shallow depths of up to 4 feet, hand excavate and tunnel under or around roots to minimize damage. Provide trench excavation protection at excavations to minimize trench width, use only vertical trench walls. Where necessary, cut roots over 1 inch in diameter with sharp pruning instruments to leave a smooth, clean-cut surface. 3. Do not allow exposed roots to dry out before permanent backfill is placed. Provide temporary earth cover, or wrap with burlap. Water and maintain exposed roots in moist condition and temporarily support and protect from damage until permanently covered with soil. k. Grading and Filling Around Trees. 1. Maintain existing grade within the dripline of trees, unless otherwise indicated. 2. Where existing grade around trees is above new finish grade, under supervision of Project Forester, carefully hand excavate within the dripline to make transition to new finish grade. 3. Where existing grade is below new finish grade, place clean bank sand in a single layer to make the transition to new grade. Do not compact. Hand grade to required elevation. l. Demolition of Existing Concrete. 1. Caution should be used during removal of the existing street and curb to minimize damage to root systems. The following procedures shall be used when removing the existing concrete: a. Zero curb cut - damage behind the curb within root zones of trees designated for zero curb cut shall be prohibited. If the curb cannot be removed without disturbing soil or damaging roots back of the curb when using equipment for demolition purposes, the curb shall

6 be broken using a hand-held jackhammer and removed by hand. b. Root removal - roots extending into the street in areas to be paved shall be cut and removed by hand prior to disturbance or removal with equipment. Roots shall be pruned flush with the proposed back of curb. Roots one inch in diameter and larger shall be cut in a manner to provide a smooth, clean cut surface. Cuts shall be made with the appropriate pruning shears or pruning saws. Roots shall not be chopped or broken. 7. Sequence of Tree Protection Procedures and Services. 1. Fertilize all designated trees. Fertilizing should be accomplished first, however, it will be determined by the time of year the project begins. Fertilizing shall be accomplished between the months of November and May. 2. Root prune and install vapor barrier (if applicable) prior to site work. 3. Place tree protection fence around designated trees. Place fencing prior to any construction activity. 4. Trim trees to clear limbs feet above surface of proposed street. 5. During removal of curb and street, hand cut roots flush with back of curb after curb and street debris has been removed and prior to any excavating or grading. 6. Cover any exposed roots with recommended materials to prevent desiccation and soil contamination by the lime slurry. 7. Root prune for utility construction purposes prior to excavating. 8. Remove tree protection fences upon completion of project. 8. Existing Stressed & Declining Trees. Trees which appear stressed or declining in health are as shown in the plans. Prior to beginning the construction phase, all trees should be reviewed and stressed or declining trees should be documented. 9. Protecting Exposed Roots. Protect exposed roots and root tips from drying out. Cover exposed roots and root tips with soil, mulch, or wet burlap within 24 hours of exposure. 10. Site Monitoring. a. It is recommended that the Project Forester as shown in the plans is hired to enforce and monitor the tree preservation program during demolition and construction to ensure tree protection procedures and techniques are practiced as specified

7 and to address concerns and conditions which occur in-the-field. b. The program must be monitored a minimum of two times weekly to ensure proper tree preservation techniques and procedures are practiced. Monitoring will be required more frequently at the beginning of the project until techniques and procedures are understood by all parties involved. c. Tree protection procedures and practices as outlined in these specifications should be reviewed at the preconstruction meeting. The Project Urban Forester should be responsible for presenting this information during the preconstruction meeting. addition, the Project Urban Forester should address the subcontractors, laborers and equipment operators in a brief meeting in order to ensure that all parties understand the requirements and the importance of the tree preservation program. In 11. Accidental Spill of Toxic Materials. Concrete, lime or other chemicals accidentally spilled within root zone protection areas should be completely removed. Contaminated soil should be completely removed at the time of the spill and removed by hand making certain that tree roots are not disturbed. fresh soil should be added as necessary to bring the soil level to that of natural grade. 12. Damage to Existing Trees. The Contractor should be assessed for damages to trees designated to be protected that result from the Contractor s negligence or failure to comply with the requirements of this specification. Damages should be assessed in accordance with the criteria established in the guide for plant appraisal, 8th edition, by the International Society of Arboriculture. Damages at the rate applicable therein should be deducted from any monies due the Contractor as liquidated damages. 13. Care of Trees After Construction is Complete. a. Proper maintenance should include fertilizing the trees once yearly and maintaining adequate moisture conditions to ensure the trees do not experience moisture stress. b. After construction is complete the trees designated for fertilizing and watering should be maintained for a minimum of two (2) years as per the fertilizing and watering specifications designated in the construction documents. Trees designated to be fertilized should be fertilized one time per year for a period of two (2) years after construction is complete. 14. Measurement. This Item will be measured as each tree treated as herein specified. 15. Payment. The work performed and materials furnished in accordance with this Item and measured as provided under measurement will be paid for at the unit price bid for tree preservation and treatment. This

8 price shall be full compensation for trimming, chemical treatment, vapor barrier (if applicable) for furnishing all required materials, including backfill, excavation, tools, labor, equipment, inspection and testing as required, and incidentals required to complete this work. Tree protection fencing shall be paid for under Item Watering shall be paid for under Item