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(1) Tree canopy requirements shall apply to all new residential development applications within unincorporated urban growth areas. The following activities are exempt from the tree canopy requirements of this section:

(a) Removal of any hazardous, dead or diseased trees, and as necessary to remedy an immediate threat to person or property as determined by a letter from a qualified arborist;

(b) Construction of a single-family dwelling, duplex, accessory or non-accessory storage structure on an individual lot created prior to April 21, 2009 or created by a subdivision or short subdivision for which a complete application was submitted prior to April 21, 2009;

(c) Construction or maintenance of public or private road network elements, and public or private utilities including utility easements not related to development subject to chapter 30.23A, 30.34A, 30.41G or 30.42E SCC;

(d) Construction or maintenance of public parks and trails when located within an urban residential zone; and

(e) Pruning and maintenance of trees.

(2) All significant trees within any perimeter landscaping required pursuant to SCC 30.25.020, critical area protection areas and required buffers shall be retained, except for trees exempted by subsection (1) of this section.

(3) Development subject to the requirements of subsection (1) of this section shall meet the minimum tree canopy coverage requirements set forth in SCC Table 30.25.016(3), except as provided in subsections (5) and (8) of this section. On sites that do not meet the requirements of SCC Table 30.26.016(3) through existing tree canopy or where an applicant removes the existing tree canopy, new plantings to meet the requirements of SCC Table 30.25.016(3) shall be planted pursuant to SCC 30.25.015(5) through (7) and subsection (6) of this section. For sites requiring new plantings to attain the required tree canopy percentage, tree canopy coverage requirements listed in SCC Table 30.25.016(3) shall be calculated according to projected growth at 20 years maturity consistent with Table 30.25.016(4).

(a) Tree canopy shall include all evergreen and deciduous trees six feet in height or greater, excluding invasive species or noxious weeds, within the gross site area.

(b) Existing or planted tree canopy may include street trees and may be located within perimeter landscaping, site landscaping, critical area protection areas and required buffers, and open space tracts or easements.

Table 30.25.016(3) Tree Canopy Coverage Requirements

Type of Development

Required Tree Canopy Coverage of Development Site (gross site area)

Subdivisions for Single Family Residential

10 or more lots

30 percent

Short Subdivisions for Single Family Residential

4 to 9 lots

25 percent

Short Subdivisions for Single Family Residential

Less than 4 lots

20 percent

Single Family Detached Units, Cottage Housing, Townhouse, Multi-family

10 or more units

20 percent

Single Family Detached Units, Cottage Housing, Townhouse, Multi-family

Less than 10 units

15 percent

Urban Center (residential and mixed use projects only)

15 percent

(4) Site tree canopy shall be measured according to SCC Table 30.25.016(4). Calculation of existing and new tree canopy shall be submitted in writing by a qualified landscape designer or a licensed land surveyor.

Table 30.25.016(4) Measuring Tree Canopy

Existing Canopy

New Canopy

Option 1 Tree Survey

Option 2 Aerial Estimation

20-Year Canopy Calculation

•    Measure average canopy radius (r) for each tree to be retained

•    Calculate existing canopy area using the formula: Canopy Area (CA)=πr2

•    Total the sum of tree canopy areas and divide by gross site area to obtain canopy coverage percentage

•    Obtain aerial imagery of site

•    Measure site boundaries

•    Measure canopies of individual trees or stand area using leading edges as the forest boundary

•    Divide total canopy measurement by the gross site area to obtain canopy coverage percentage

For each proposed species:

•    Calculate radius (r) of canopy at 20 years maturity

•    Calculate canopy coverage using the formula: CA=πr2

•    Multiply by the proposed quantity to be planted to obtain total species canopy area

•    Total the sum of species canopy area for all proposed species and divide by gross site area to obtain 20-year canopy coverage percentage

(5) To assist in the preservation and retention of significant trees and existing tree canopy outside of critical area protection areas and required buffers and perimeter landscaping, the applicant may utilize the following credits:

(a) Individual significant trees retained on site shall be counted at 125 percent of their actual canopy area.

(b) For clusters or stands of five or more trees, each tree shall be counted at 150 percent of its actual canopy area.

(c) For clusters or stands of five or more significant trees, each tree shall be counted at 200 percent of its actual canopy area.

(d) Retained trees located within no more than 20 feet of a rain garden or a bio-swale on site shall be counted at 150 percent of their actual canopy area.

(e) Retained significant trees qualified to receive flow control credits under Appendix III-C of the Snohomish County Drainage Manual shall be counted at 150 percent of their actual canopy area.

(f) The on-site recreation space required by SCC 30.23A.080 may be reduced by 100 percent if 40 percent or more of the site has existing tree canopy that is retained along with all native vegetation under that canopy area.

(g) A project may be exempted from all other requirements of SCC 30.25.015 and this section if the canopy area of significant trees retained onsite is 45 percent or more of the gross site area and the majority of the canopy is provided by evergreen species.

(h) The minimum required lot area in subdivisions or short subdivisions not using the lot size averaging provisions of SCC 30.23.210 may be reduced by 20 percent when at least 20 percent of the site, not including any critical area protection areas and perimeter buffers, is put into a separate tract or tracts that have at least 20 significant trees per acre and where at least 60 percent of the significant trees within the tract or tracts are retained. This does not change the tree canopy requirements.

(i) For subdivisions or short subdivisions using the lot size averaging provisions of SCC 30.23.210(7), the minimum size for each single lot in SCC 30.23.210(7)(a) may be reduced by 20 percent when at least 20 percent of the site, not including any critical area protection areas and perimeter buffers, is put into a separate tract or tracts that have at least 20 significant trees per acre and where at least 60 percent of the significant trees within the tract or tracts are retained. This does not change the tree canopy requirements.

(6) In addition to the requirements of SCC 30.25.015(5) through (7), trees planted to meet tree canopy requirements in SCC Table 30.25.016(3) shall meet the following criteria:

(a) Sites must be planted or replanted with a minimum of 50 percent evergreen species, except:

(i) The evergreen portion of the required planting mix may be reduced to 37.5 percent when the deciduous mix contains exclusively indigenous species to the Puget Sound region, not including Alder; and

(ii) Sites obtaining tree canopy requirements solely through street trees are exempt from the requirement to include evergreen species in the planting mix;

(b) Sites requiring planting or replanting of tree canopy must plant no more than 30 percent of trees from the same species and no more than 60 percent of trees from the same taxonomic family.

(c) Replacement trees shall be planted in locations appropriate to the species’ growth habit and horticultural requirements;

(d) When preparing the landscaping plan, applicants are encouraged to meet the requirements of SCC Table 30.25.016(3) by conserving existing tree canopy including significant trees and other vegetation located on the site and place new plantings in protected areas (such as street trees, perimeter landscaping, open spaces and critical area protection areas and required buffers) at healthy spacing densities before placing trees within individual lots or yards; and

(e) Replacement trees shall be located in such a manner to minimize damage to trees or structures on the project site and on properties adjoining the project site.

(7) The following tree protection measures shall be taken during clearing or construction:

(a) Tree protective fencing shall be installed along the outer edge of the drip line surrounding the trees retained in order to protect the trees during any land disturbance activities, and fencing shall not be moved to facilitate grading or other construction activity within the protected area;

(b) Tree protective fencing shall be a minimum height of three feet, visible and of durable construction; orange polyethylene laminar fencing is acceptable; and

(c) Signs must be posted on the fence reading "Tree Protection Area."

(8) An applicant may reduce the tree canopy requirements of SCC Table 30.25.016(3) by no more than five percent through a landscape modification when all of the following criteria and those in SCC 30.25.040 are met:

(a) The applicant demonstrates in writing that they have made a good faith effort to comply with the tree canopy requirements within the physical constraints of the site by:

(i) Retaining as much of the tree canopy as possible on site consistent with best management practices for maintaining the health of trees; or

(ii) Replanting as much of the tree canopy as possible on site consistent with best management practices for maintaining the health of trees;

(b) The applicant proposes to plant additional understory vegetation or ground cover area, excluding lawn cover, invasive species or noxious weeds, to fulfill the remaining canopy requirement in SCC Table 30.25.016(3) not met by retention or replanting of tree canopy; and

(c) When critical areas protection area buffers exist on site and those buffers are not highly functioning, the applicant proposes to enhance the buffers by removing invasive species and noxious weeds and/or planting vegetation indigenous to the Pacific Northwest, spaced for maximum survivability.

(9) On sites without any existing tree canopy, the director may reduce the requirements of SCC Table 30.26.016(3) by no more than five percentage points (for example, 30 percent requirement can be reduced to 25 percent) when an applicant provides a 25 percent increase in the area of open space than that required under SCC Table 30.23A.080(2). The following shall not be eligible for this reduction:

(a) Short subdivisions less than seven lots;

(b) Single family detached units, cottage housing, townhouse, multi-family less than 10 units; and

(c) Urban center development.

(10) The county engineer may modify required frontage improvements to retain significant trees as street trees.

(11) Retained significant trees, trees planted as replacements for significant trees, and trees planted to meet requirements in subsection (3) of this section may not be removed except when determined in writing by a certified arborist to constitute a hazard. Any replacement or significant trees removed without proper documentation from a certified arborist shall be subject to a fine as determined under chapter 30.85 SCC.

(12) Any significant trees identified in a landscape plan to be retained and subsequently damaged or removed during site development shall be replaced at a rate of three trees for each one damaged or removed significant tree. Failure to replace damaged or removed significant trees shall be subject to a fine as determined under chapter 30.85 SCC. (Added by Amended Ord. 08-101, Jan. 21, 2009, Eff date Apr. 21, 2009; Amended by Amended Ord. 14-073, Oct. 8, 2014, Eff date Oct. 27, 2014).