Tree Preservation and Tree Protection Plans

Tree protection is essential during construction projects to protect existing trees in and near construction projects. Protection is focused on the tree, and the tree protection zone (TPZ), the area of the tree's dripline, directly under the outer circumference of the tree's branches.  This is a critical area to protect, as roots located here provide stability and access to nutrients for the tree. Trenching, paving, storing construction equipment or materials and driving heavy equipment across unprotected roots or altering drainage patterns within and near this area can hurt the tree, or require the tree be removed. 

The following specifications should be incorporated into the tree protection plan for projects that may impact trees. A tree protection plan should be determined for each tree that is to be preserved for any development project. While it is seldom possible to save every tree at a construction site, the following provisions and principles can apply to most situations to sustain vigor and minimize adverse growing conditions. Whenever possible, the City encourages the inclusion of existing trees into development design and planning.

The City provides guidance for projects needing tree protection plans. Please see the linked handout for more information on small projects and tree protection plans: Small Projects and Protected Trees

Preservation Specifications

1. Proposed development plans and specifications shall prepare a tree protection plan for existing trees to be preserved for the project. Any tree care practices, such as cutting of roots or pruning, shall be adequately described and shall be approved by the Urban Forestry Program Manager or Urban Forestry Program representative. Damage to or illegal removal of existing trees shall be a violation of Chapter 37 of the Davis Municipal Code and penalties can be levied.

2. Trees shall be fenced prior to construction. Soil compaction under trees is to be avoided. The fence shall prevent equipment traffic, material storage under the trees, and parking of construction vehicles from under the trees and should extend just beyond the dripline. Excavation within this zone shall be accomplished by hand, and roots 2" and larger shall be preserved. No encroachment within 5 feet of a trunk will be permitted under any circumstances. 

3. Proper fertilization and irrigation prior to, and during the construction period shall be provided as specified in the tree protection plan.

4. New landscaping under existing trees shall be carefully planned to avoid any grade changes and any excess moisture in the trunk area. Existing plants which are compatible as to irrigation requirements and which compliment the trees as to color, texture and form are to be saved.

5. Trenching within the dripline shall be performed only with prior approval of the Urban Forestry Program Manager or their designee. Directional boring is preferred when feasible. Avoid exposing roots during hot, dry weather. Backfill trenches as soon as possible with soil and soak with water the same day. Small roots can die in 10 to 15 minutes and large roots may not survive an hour of exposure. If the trench must be left open all roots must be kept moist by wrapping them in peat moss and burlap.

6. All paving plans and specifications shall clearly prohibit the use of soil sterilants adjacent to preserved trees.

7. Grade changes within the dripline shall be avoided, and nothing other than a saw shall be used for root cutting.

8. It is the property owner or designated representatives responsibility to ensure that all trades/subcontractors and utility companies abide by tree protection plan conditions.

9. From the conception of plans, architects, developers, engineers and/or planners shall locate and identify all existing trees on proposed project site plans and shall make every effort to comply with the City policies for tree protection.

10. The tree protection plan shall include a list of activities prohibited within the Tree Protection Zone: 

    1. Parking vehicles or equipment, storage of building materials, refuse, or excavated soils, or dumping poisonous material on or around trees and roots. Poisonous materials include, but are not limited to paint, petroleum products, concrete, stucco mix, dirty water or any material that may be harmful to tree health.
    2. The use of tree trunks as a backstop, winch support, anchorage, as a temporary power pole, signpost or other similar function.
    3. Cutting of tree roots by utility trenching, foundation digging, placement of curbs and trenches, or other miscellaneous excavations without prior approval of the Urban Forestry Program Manager or designee.
    4. Soil disturbance or grade change.
    5. Drainage changes.
       
       
11. Providing adequate maintenance can mitigate stressful changes that occur to a tree’s environment during construction. To remain vigorous, the tree needs to maintain stored carbohydrates and preserve the effectiveness of its growth regulators. It is recommended that large projects provide: 
    
    Irrigation 
    Providing supplemental irrigation for trees under water stress may be the single most important treatment. Irrigation should be designed to wet the soil within the TPZ to the depth of the root zone and to replace that water once it is depleted. Light, frequent irrigation should be avoided. Create a six-inch berm around trees at the edge of the TPZ and fill with no more than six inches of mulch. Fill the basin with water. Irrigation should wet the top two to three feet of soil to replicate similar volumes and normal seasonal distribution. 
    
    Soil Compaction Mitigation 
    To prevent negligent encroachment into the TPZ, trees to be preserved during construction must have the specified type of protection fences in place at all times.
    
    Removal of fences, even temporarily, to allow deliveries or equipment access is not allowed unless approved by the Urban Forestry Program Manager and a Root Buffer is installed. The Root Buffer components: mulch, gravel and plywood, must be maintained continually to assure its effectiveness against soil compaction. 

Note that any preservation measures put into place as approved in the tree protection plan must remain in place until the conclusion of the project.