Division 13-18-004
Installation, Placement, and Planting
Sections:
13-18-004-0001 General Requirements
13-18-004-0001.1 Execution
13-18-004-0001.2 Safety
13-18-004-0002 Warranty
13-18-004-0003 Finish Grading
13-18-004-0003.1 Berms
13-18-004-0003.2 Drainage Courses
13-18-004-0004 Pre-Installation Weed Control Treatment
13-18-004-0005 Trees
13-18-004-0005.1 Street Trees
13-18-004-0005.2 Urban Street Trees
13-18-004-0005.3 Root Control
13-18-004-0005.4 Structural Soils
13-18-004-0005.5 Root Barriers
13-18-004-0005.6 Staking
13-18-004-0005.7 Wrapping
13-18-004-0006 Hardscape
13-18-004-0007 Landscape Boulders and Rockwork
13-18-004-0008 Hydroseeding
13-18-004-0001 General Requirements
A. Except for ground cover, placement of landscape materials shall respect the width of the planting area such that adequate clearance is maintained between curbs and plant materials so as to minimize damage from snow removal, cindering operations, and vehicular traffic.
B. All landscape materials shall be placed, including the quantity and spacing of plant materials, in accordance with a streetscape plan consistent with landscape design industry standards and approved by the City Engineer.
C. Nothing shall be planted during freezing or excessively windy, hot, or wet weather or otherwise when the conditions cannot be properly worked for digging, mixing, raking, or grading. Nothing shall be planted until the adjacent site improvements, pavements, irrigation installation and finish grading are completed.
D. Certain landscape elements, particularly hardscape elements, are subject to other codes and standards and require permits. These standards are in addition to other requirements and do not in any way alter, diminish, or alleviate other requirements. (Ord. 2017-22, Rep&ReEn, 07/05/2017)
13-18-004-0001.1 Execution
A. Excavation.
1. Plant material locations shall be laid out in the field, as shown on the plan(s). Incorrectly placed plants shall be relocated at no expense to the City.
2. The planting pit shall be excavated to provide at least six (6) inches of planting soil backfill around and beneath the root system.
3. Where conditions prevent digging a planting pit as required, obtain approval from the City to modify the location and/or dimensions.
4. Planting soil for backfilling shall be kept separate from excavated subsoil material.
5. Trees shall be planted with the root flare one (1) inch above finish grade.
B. Ground Cover Installation.
1. Immediately prior to installation, ground cover areas are to be cultivated to a depth of six (6) inches and grade smooth and uniform.
2. Ground cover shall be planted to within eighteen (18) inches of tree trunks or shrubs planted within the area. Ground cover is to be planted so that the root crown is at or slightly above the prepared bed’s finish grade.
3. After planting of ground cover and prior to mulching, pre-emergent weed control shall be spread over planting bed soil surface in accordance with the manufacturer’s written directions.
4. Specified mulch shall be installed to a depth of two (2) inches over the entire ground cover bed.
C. Container and Balled and Burlapped (B&B) Plant Material Installation.
1. Nonplantable containers shall be removed prior to planting in a manner that does not disturb the potted soil or root ball.
2. Plantable containers are to be removed in the same manner as nonplantable containers. If the plantable container is left in place, any part of the container that extends above the soil level within the container is to be removed and a minimum of three (3) full height cuts in the container sides shall be made.
3. The root ball shall be set on six (6) inches of firm planting soil, plumb and in the center of the pit with the root ball crown slightly above the same elevation as adjacent finished landscape grades.
a. Wire, twine, natural burlap, and other material on the upper one-third (1/3) of the root ball of B&B stock shall be completely removed.
b. After the root ball has been placed in its final location, wire baskets and as much synthetic burlap as possible shall be removed.
4. Backfill material shall be added around base and sides of root ball after the plant is set with each layer to be worked for purposes of settling backfill and eliminating voids and air pockets.
a. When excavation is approximately two-thirds (2/3) full, water thoroughly before placing the remainder of the backfill. Repeat watering until no more is absorbed.
b. Water again after placing the final layer of backfill.
5. Mulch shall be placed at a depth of two (2) to three (3) inches in the area disturbed by excavation of the planting well or in planting bed areas as designated on the plan(s).
a. Pre-emergent herbicide shall be applied prior to mulch installation in all planting beds.
b. Mulch shall be installed by the end of each work day for all plant material installed during that day.
D. Staking and Guying.
1. Single stem, deciduous trees between one (1) and three (3) inch caliper and evergreen trees between six (6) and eight (8) feet in height shall be firmly tied between two (2) vertically driven stakes.
2. Single stem, deciduous trees over three (3) inch caliper and evergreen trees more than eight (8) feet in height shall be guyed with three (3) lines spaced evenly about the tree.
a. Line shall attach to the tree trunk about two-thirds (2/3) of the tree height and be anchored at the ground to the specified earth anchors at a thirty (30) to forty-five (45) degree angle.
E. Miscellaneous Work.
1. Dead or damaged branches shall be pruned and removed from the plant material. Make all cuts at branch collar. The natural habit, shape, and specified size of plant material is to be maintained.
2. All single stem, deciduous trees shall be wrapped from the ground line up to and including the crotch formed by the first major branch.
a. Wrapping shall be done after the plant has been installed.
3. Remove all tags, labels, and/or other material on plant.
4. The contractor shall be responsible for legal disposal of excess soil, packing material, burlap, trimmings, and other debris associated with the planting operation.
a. Paved surfaces shall be broom cleaned.
b. Clean up work shall be considered incidental to the work.
5. If planting work is performed after lawn preparation is finished, the contractor shall provide protection to the lawn areas and immediately repair any damage resulting from planting operations at no cost to the City.
6. Maintenance of plants shall commence immediately and continue until acceptance of the work. A written recommended maintenance program is to be provided to the City prior to acceptance of the work.
a. Maintenance performed by the City in accordance with the recommended program shall not affect the contractor’s obligation to guarantee and replace defective plant material. (Ord. 2017-22, Rep&ReEn, 07/05/2017)
13-18-004-0001.2 Safety
A. Lines of Sight. At intersections and driveways, landscaping proposed to be located within the line of sight shall be selected for and maintained at a maximum three and one-half (3 1/2) feet top height. Trees located within or overhanging shall have canopies selected for and maintained at eight (8) feet above street level. Medians at intersections shall be treated in the same manner. See diagram below and Section 13-10-006-0002 for Intersection Sight Triangles, Clear View Zones.
B. Blockage. Landscaping materials should be placed and/or maintained so that they do not interfere with street lighting, traffic signs, access to fire hydrants and similar emergency apparatus, overhead or underground utilities, or operational needs within rights-of-way.
1. Trees and shrubs shall not be placed within fifteen (15) feet of emergency apparatus.
2. Trees and shrubs shall not be placed within ten (10) feet of light standards, overhead or underground utilities, or utility boxes and similar items within rights-of-way that require service operations.
C. Winter Icing. Landscaping materials should be selected and placed so as to minimize winter icing on roads, walkways, and other paving. Placement relative to winter sun angles, spacing, type as deciduous or conifer, and material density should be taken into consideration. (Ord. 2017-22, Rep&ReEn, 07/05/2017; Ord. 2024-13, Amended, 4/16/2024 (Res. 2024-15))
13-18-004-0002 Warranty
Plants that do not survive during the first year after planting shall be replaced with variety and size to match the original plant material. Private parties performing work within rights-of-way shall warrant plant material to remain alive and be in a healthy, vigorous condition for a period of one (1) year after acceptance. Warranty shall specifically include rodent control during the warranty period. Warranty shall not include damage caused by fires, floods, drought, freezing rains, lightning storms, winds over seventy-five (75) miles per hour, winter kill caused by extreme cold and severe winter conditions not typical of planting areas, acts of vandalism or negligence on the part of the City. (Ord. 2017-22, Rep&ReEn, 07/05/2017)
13-18-004-0003 Finish Grading
13-18-004-0003.1 Berms
Where space permits, earthen berms may be incorporated into finish grading. Berms shall be between two (2) and six (6) feet high, gently rolling, free form ground sculpture. The top of berms should be undulating to provide a natural appearance. The ridge of berms should have an area at the top that is rounded (i.e., neither flat nor meeting at the peak). The sides of the berm should not exceed a 3:1 slope ratio. (Ord. 2017-22, Rep&ReEn, 07/05/2017)
13-18-004-0003.2 Drainage Courses
Swales and similar drainage courses shall be designed as gently rolling, free form ground sculpture with a natural appearance. Where space and hydrological needs permit, they should be broad shallow channels with established vegetation designed to promote infiltration and trap pollutants. Dissipation structures, if any, shall be designed to be as natural in appearance as possible such as the use of rock lining. (Ord. 2017-22, Rep&ReEn, 07/05/2017)
13-18-004-0004 Pre-Installation Weed Control Treatment
A. Existing weeds, including roots, are to be completely removed prior to planting.
B. Soil solarization is the preferred method for weed control when time permits. Manual, mechanical, and chemical treatments are acceptable methods.
1. Adverse environmental impacts shall be considered when using chemical treatments and materials.
2. Particular attention shall be paid to protection of standing water bodies and waters directed into drainage courses. (Ord. 2017-22, Rep&ReEn, 07/05/2017)
13-18-004-0005 Trees
A list of pre-approved trees, shrubs, and ground cover is provided in the zoning code found in Title 10. (Ord. 2017-22, Rep&ReEn, 07/05/2017)
13-18-004-0005.1 Street Trees
A. Street trees shall avoid random changes in species installed in public rights-of-way for all developments and shall be typically planted midway between curb and walk at a minimum of forty-five (45) foot intervals. Any existing specimen or mature street tree shall remain and shall be considered a planted tree for purposes of meeting spacing requirements.
B. Tree placement should consider visibility of signage and storefronts, as well as public views and shall be located offset from building entrances. (Plant trees in accordance with Standard Detail 18-04-050.) (Ord. 2017-22, Rep&ReEn, 07/05/2017)
13-18-004-0005.2 Urban Street Trees
Urban street trees shall typically be placed in accordance with the following schedule:
|
Tree Size |
Spacing |
|---|---|
|
Small |
10 to 15 feet |
|
Medium |
15 to 20 feet |
|
Large |
20 to 25 feet |
A list of pre-approved trees is provided in the zoning code found in Title 10.
A. Structural Soils. Structural soil mixes shall be used in urban and tree grate situations. Structural soil mixes shall be submitted to the City of Flagstaff for prior approval. See Section 13-18-003-0006.7 for recommended design mix.
B. Site Disturbances.
1. Verify locations and clearance depths of underground utilities prior to excavation work.
2. Verify location and clearance heights of overhead utility lines, architectural items, site accessories, street lights, and/or other installed/constructed items.
3. Perform work in a manner to avoid damage.
C. Planting with Improved Substrate (Underlying Base) and Tree Grates.
1. Provide approximately three hundred (300) cubic feet of improved substrate material for each urban street tree.
2. Substrate below proposed walks and pavements, adjacent to proposed street tree locations, shall be backfilled with the structural soil mix specified in Section 13-18-003-0006.7.
a. Structural soil shall be placed in six (6) to eight (8) inch lifts and mechanically compacted to not less than ninety-five percent (95%) standard Proctor density (AASHTO T-99).
b. A six (6) inch base course of clean, loose, rounded stone (e.g., river rock) shall be installed and overlaid with a geotextile soil separator.
c. Tree shall be planted in accordance with Section 13-18-004-0001.1.
See Detail Drawing 18-03-050.
D. Tree Grate Installation.
1. Tree grates shall comply with the requirements of the Americans with Disabilities Act (ADA).
2. Grates shall allow for breakaway ring removal to expand the opening.
3. Rectangular or square tree grates shall have a minimum grate area of twenty-four (24) square feet. Circular tree grates shall have a nominal minimum grate area of twenty-three and three-quarters (23.75) square feet (five and one-half (5.5) foot diameter).
4. Tree grate and frame shall be installed in accordance with the manufacturer’s written instructions.
5. If large area tree grates are not available or cannot be used, multiple tree grates may be used to effectively create a single tree grate around the tree with the use of permeable materials (e.g., pavers) over the remainder of the specified minimum area.
E. Staking and Guying. Trees located within tree grates shall not require staking or guying. (Ord. 2017-22, Rep&ReEn, 07/05/2017)
13-18-004-0005.3 Root Control
Trees planted within four (4) feet of buildings, roads, walkways, and similar situations, shall be provided with root control system specified in Section 13-18-004-0005.5. (Ord. 2017-22, Rep&ReEn, 07/05/2017)
13-18-004-0005.4 Structural Soils
Structural soil mixes are two (2) phase systems comprised of a stone skeleton or lattice for strength, and soil for horticultural needs. Proprietary distributors shall provide specifications, compaction data, and testing results. Designs shall be submitted that support the long-term health of the tree and minimize heaving of adjacent paving. (Ord. 2017-22, Rep&ReEn, 07/05/2017)
13-18-004-0005.5 Root Barriers
Root barriers shall be one (1) continuous piece (not interlocking), shall be a minimum of twenty-four (24) inches in depth, and installed such that the top is even with the top of pavement. (Ord. 2017-22, Rep&ReEn, 07/05/2017)
13-18-004-0005.6 Staking
A. Staking and strapping shall be provided for all tree installations. Stakes are to be driven three (3) feet vertically into firm soil outside the plant pit and shall be placed according to tree height or caliper as follows:
1. Deciduous trees two (2) inches and under - one (1) stake oriented northwest.
2. Deciduous trees larger than two (2) inches but less than three (3) inches and evergreen trees less than five (5) feet in height - two (2) stakes oriented northwest and southeast.
3. Deciduous trees three (3) inches and larger and evergreen trees five (5) feet and larger - three (3) stakes with one (1) oriented northwest and the other two (2) oriented one hundred twenty (120) degrees in either direction from northwest.
Stakes shall be parallel or slightly angled away from the trunk.
B. A double strand of wire shall be run through one (1) grommet in the strap, the strap wrapped around trunk at no more than one-third (1/3) the height of tree, after which the wire shall be run through other grommet and back to stake.
1. Strap and wire attachment between the stake and tree shall be adjusted so that straps are under just enough tension to avoid visible sag in lines.
a. Rigid guying shall not be accepted.
b. Straps and wires shall be placed so as to be perpendicular to the trunk. (Ord. 2017-22, Rep&ReEn, 07/05/2017)
13-18-004-0005.7 Wrapping
A. All deciduous trees shall be wrapped between October 15th and November 30th of the year in which they are planted. Specified tree wrap shall be cut in a continuous strip of sufficient length to wrap the tree. This wrapping shall begin at the ground line with overlapping wraps of one and one-half (1-1/2) inches terminating above the lowest main branch of the tree.
1. Final wrap shall be secured with tape in at least three (3) places.
B. Tree wrap should be removed between April 1st through 15th of the following spring. (Ord. 2017-22, Rep&ReEn, 07/05/2017)
13-18-004-0006 Hardscape
This title provides standards for the design and construction of medians and parkways, sidewalks, and similar hardscape elements, and is incorporated herein by reference. (Ord. 2017-22, Rep&ReEn, 07/05/2017)
13-18-004-0007 Landscape Boulders and Rockwork
A. Boulders may be incorporated into landscaping of rights-of-way in a manner that reflects the character of the community’s natural environment.
1. Selected boulders shall be native to the region unless an alternate selection is used and approved for a specific design effect.
2. Boulders shall have rounded natural edges and a character and shape consistent with natural rock settings.
3. No split, bruised face, slab type, layered or slide boulders shall be used without prior approval and acceptance.
B. Boulders shall be set on compacted native material and shall be set into the finish grade, approximately one-third (1/3) the depth of the boulder.
C. Rockwork joints shall be made tight by butting natural faces together in place. Soil grades shall be adjusted to stabilize rocks in position and regraded in place to establish the placement of each rock so that they blend naturally into adjacent terrain. Rockwork is to be placed by terracing or stepped layers to achieve a naturalized effect. (Ord. 2017-22, Rep&ReEn, 07/05/2017)
13-18-004-0008 Hydroseeding
Hydroseeding means, materials and methods are described and specified under Chapter 13-17, Erosion Control. (Ord. 2017-22, Rep&ReEn, 07/05/2017)