Chapter 12.50 CANYON CREEK/39TH AVENUE SE SUBAREA REGULATIONS

Chapter 12.50
CANYON CREEK/39TH AVENUE SE SUBAREA REGULATIONS

Sections:

12.50.020 Canyon Mobile Park mobile home park overlay – R 9,600 zoning on 228th Street SE.

12.50.030 Protection of groundwater resources.

12.50.040 Preservation of the hydrologic cycle within the North Creek Fish and Wildlife Critical Habitat Protection Area (NCFWCHPA).

12.50.050 Wildlife standards within the North Creek Fish and Wildlife Critical Habitat Protection Area (NCFWCHPA).

12.50.060 Definitions.

12.50.010 Purpose.

Subarea zoning regulations implement subarea-specific policies in the Imagine Bothell... Comprehensive Plan. The subarea zoning regulations in this chapter apply specifically to land within the Canyon Creek/39th Avenue SE Subarea. Subarea zoning regulations are in addition to city-wide zoning regulations or, where more restrictive, take the place of city-wide zoning regulations. (Ord. 2053 § 3 (Exh. C), 2010; Ord. 1946 § 2, 2005; Ord. 1629 § 1, 1996).

12.50.020 Canyon Mobile Park mobile home park overlay – R 9,600 zoning on 228th Street SE.

Development shall be limited to the existing mobile home park (MHP) and any additional mobile or manufactured homes which may be permitted by existing approvals or by new approvals obtained under Chapter 12.08 BMC. Redevelopment to uses other than a mobile home park shall require prior review and approval of an amendment to the Imagine Bothell... Comprehensive Plan. (Ord. 2053 § 3 (Exh. C), 2010; Ord. 1957 § 1 (Exh. B), 2006; Ord. 1946 § 2, 2005; Ord. 1629 § 1, 1996).

12.50.030 Protection of groundwater resources.

The Palm, Woods and Cole Creek drainage basins within the Canyon Creek/39th Ave SE Subarea have been identified as particularly important sources of cool water for North Creek, via groundwater and surface water movement. Cool water promotes the long-term vitality of the fisheries resources found in North Creek. Chapter 14.04 BMC, Critical Area Regulations, establishes regulations applicable city-wide for the protection of surface water bodies such as wetlands and streams. BMC 12.14.180(C), Development on Hillsides, establishes regulations applicable city-wide for the protection of groundwater movement as it may be affected by hillside development. The Bothell Surface Water Design Manual, Chapter 4 of the Bothell Design and Construction Standards and Specifications, establishes regulations applicable city-wide for the control and discharge of surface water. This section augments BMC 12.14.180(C) by establishing regulations for the protection of groundwater resources specifically within the Palm, Woods and Cole Creek drainage basins.

A. Uses or Activities with Special Requirements.

1. Vehicle Repair and Servicing.

a. Vehicle repair and servicing must be conducted over impermeable pads and within a covered structure capable of withstanding normally expected weather conditions. Chemicals used in the process of vehicle repair and servicing must be stored in a manner that protects them from weather and provides containment should leaks occur.

b. No dry wells shall be allowed in the subarea on sites used for vehicle repair and servicing. Dry wells existing on the site prior to facility establishment must be abandoned using techniques approved by the state Department of Ecology prior to commencement of the proposed activity.

2. Aboveground Tanks. All new aboveground storage facilities proposed for use in the storage of hazardous substances or hazardous wastes shall be designed and constructed so as to:

a. Not allow the release of a hazardous substance to the ground, groundwaters, or surface waters; and

b. Have a primary containment area enclosing or underlying the tank or part thereof.

3. Underground Tanks. All new underground storage facilities proposed for use in the storage of hazardous substances or hazardous wastes shall be designed and constructed so as to:

a. Prevent releases due to corrosion or structural failure for the operational life of the tank;

b. Be protected against corrosion, constructed of noncorrosive material, steel clad with a noncorrosive material, or designed to include a secondary containment system to prevent the release or threatened release of any stored substances; and

c. Use material in the construction or lining of the tank that is compatible with the substance to be stored.

4. Residential Use of Pesticides and Nutrients. Application of household pesticides, herbicides, and fertilizers shall not exceed times and rates specified on the packaging.

5. Use of Reclaimed Water for Surface Percolation or Direct Recharge. Water reuse projects for reclaimed water must be in accordance with the adopted water or sewer comprehensive plans that have been approved by the state Departments of Ecology and Health.

a. Use of reclaimed water for surface percolation must meet the groundwater recharge criteria given in RCW 90.46.010(10) and 90.46.080(1). The state Department of Ecology may establish additional discharge limits in accordance with RCW 90.46.080(2).

b. Direct injection must be in accordance with the standards developed by authority of RCW 90.46.042.

6. State and Federal Regulations. All activities, uses, and construction activities shall be in accordance with applicable state and federal regulations.

7. Uses identified by the Bothell Surface Water Design Manual as pollution-generating impervious or pervious surfaces shall be subject to the applicable water quality treatment and containment provisions of the Bothell Surface Water Design Manual.

B. Site and Building Design Standards.

1. General Requirements.

a. The applicant shall demonstrate that the proposed activity will not adversely affect the recharging of the groundwater table.

b. The proposed activity must comply with the water source protection requirements and recommendations of the U.S. Environmental Protection Agency, Washington State Department of Health, Washington State Department of Ecology, and the King and Snohomish County health districts.

2. Impervious Surface Coverage.

a. Developments shall limit the amount of impervious surface coverage on the subject parcel or parcels to the minimum coverage necessary to accommodate the development.

b. The community development director may require minor site plan modifications to reduce impervious surface coverage and to reduce driveway lengths and widths.

3. Natural Foliage Retention Requirements.

a. For the purposes of this chapter, “natural foliage” shall mean naturally occurring trees, understory plants (shrubs), groundcovers and the layer of dead leaves, needles, and vegetation (forest duff) found on the ground.

b. Developments shall limit the amount of natural foliage removed on the subject parcel or parcels to the minimum necessary to accommodate the development.

c. The community development director may require minor site plan modifications to preserve natural foliage areas and to reduce grading limits.

4. Grading Limitations.

a. Excavation shall be prohibited from intruding into that part of the groundwater table which experiences saturated soil conditions, as measured during the dry season.

b. Grading activities shall follow existing topographic contours to the maximum extent possible.

c. Changes to pre-existing ground elevations shall be minimized.

d. Use of retaining walls which allow the maintenance of existing natural slope areas is preferred over graded artificial slopes. Retaining walls and high foundations on the underside of buildings shall be screened by vegetation.

5. Structure Requirements.

a. Structures and improvements shall conform to the natural contour of the slope with foundations tiered to conform to the existing topography.

b. Standard prepared building pads (slab on grade) resulting in grading more than 10 feet outside the building footprint area are prohibited.

c. Use of common access drives and utility corridors is required where feasible.

d. Under structure parking and multilevel structures shall be incorporated where feasible.

e. Roads, walkways and parking areas shall be designed to follow the natural contours of the hillsides while maintaining consolidated areas of natural topography and vegetation. Access shall be located in the least sensitive area feasible.

f. Use of foundation walls as retaining walls is preferable to rock or concrete walls built separately and away from the building. Freestanding retaining devices are only permitted when they cannot be designed as structural elements of the building foundation.

g. Use of pole-type construction which conforms to the existing topography is preferred.

h. Structures shall be tiered to conform to existing topography and to minimize topographic modification. Piled deck support structures are preferable for parking or garages to fill-based construction types. (Ord. 2053 § 3 (Exh. C), 2010; Ord. 1946 § 2, 2005).

12.50.040 Preservation of the hydrologic cycle within the North Creek Fish and Wildlife Critical Habitat Protection Area (NCFWCHPA).

The North Creek Fish and Wildlife Critical Habitat Protection Area (NCFWCHPA) is assigned to properties within the Canyon Creek/39th Avenue SE Subarea as a special regulation to protect the known critical fish and wildlife habitat present in this subarea through low impact development (LID) and other regulations. The Palm, Woods and Cole Creek drainage basins within the Canyon Creek/39th Avenue SE Subarea have been identified as particularly important sources of cool water for North Creek, via groundwater and surface water movement. Cool water promotes the long-term vitality of the fisheries resources found in North Creek. Chapter 14.04 BMC, Critical Area Regulations, establishes regulations applicable city-wide for the protection of surface water bodies such as wetlands and streams. BMC 12.14.180(C), Development on Hillsides, establishes regulations applicable city-wide for the protection of groundwater movement as it may be affected by hillside development. BMC 12.14.140, Building and impervious surface coverage, and BMC 12.14.030, Residential area and dimensions, and BMC 12.14.040, Commercial and industrial dimensions, establish standards for maximum impervious surface. This chapter augments and amends other development codes by establishing regulations for the maintenance and restoration of the hydrologic cycle, particularly as it affects protection of surface and groundwater resources specifically within the Palm, Woods, Cole and North Creek drainage basins. This land use section shall be used in conjunction with the LID Supplement to the Bothell Design and Construction Standards and Specifications, and the Bothell Surface Water Design Manual (Bothell Standards).

A. Intent and Application. These standards are applied in addition to zoning and other code regulations. Authority is provided for the community development director and public works director to allow modification of the specific design and construction standards and regulations identified in this chapter to accommodate the provisions of low impact development as provided in this chapter.

B. Site and Building Design Regulations.

1. General Requirements.

a. The proposed activity will not adversely affect the infiltration and recharging of the groundwater table in a manner that will result in decreases in groundwater interflow to surface water.

b. The proposed activity must comply with the water source protection requirements and recommendations of the U.S. Environmental Protection Agency, Washington State Department of Health, the State Department of Ecology, and the King and Snohomish County health districts.

c. Site design and storm water facilities shall be designed in accordance with these low impact development regulations as provided herein, the LID Supplement to the Bothell Design and Construction Standards, and the Bothell Surface Water Design Manual.

2. Effective Impervious Surface Coverage.

a. Effective impervious area (EIA) shall not exceed 20 percent for lands zoned R 5,400a (LID). EIA shall be based upon the gross area of the total site. Measures to achieve this effective impervious surface standard shall include, but are not limited to, the following; provided, that a combination of measures may be used on any site to best accomplish this requirement:

(1) Minimization of impervious area from roadways and other sources through site layout;

(2) Employment of pervious surfaces on sidewalks, trails and nontraveled portions of roads;

(3) Dispersion of surface water runoff within preserved forest area through gravity systems;

(4) Infiltration of runoff through bioretention facilities adjacent to impervious surfaces consisting of swales with amended soils, or similar facilities;

(5) Infiltration of runoff from roof areas including dispersion to soil amended lawn areas, downspout infiltration or bioretention facilities;

(6) Employment of vegetated roofs;

(7) Engineered infiltration systems other than bioretention.

b. Transfer of Credit for Effective Impervious Area. Any property within the Canyon Creek/39th Avenue SE Subarea with NCFWCHPA LID zoning may transfer credits for effective impervious surface to other sites within the Canyon Creek/39th Avenue SE Subarea with NCFWCHPA LID zoning subject to the following provisions. All EIA transfers, allocations, limitations, provisions and stipulations shall be identified within a covenant document which is reviewed and approved by the community development director. The covenant document shall be a permanent covenant running with the land in perpetuity filed and recorded with the Snohomish County auditor:

(1) EIA credits may be transferred from undeveloped sending properties and shall be in the form of square feet of EIA allocation, provided the following are met:

(A) The EIA allocation for the sending property as a whole shall be calculated and the amount to be retained for the sending property and the amount to be transferred to the receiving property shall be clearly described within the covenant document;

(B) The future development limitations proposed for the sending property transferring the credits shall be described including the specific number of units and total impervious surface needed to support any future development. The feasibility of meeting EIA standards shall be demonstrated for the nontransferred allocation, unless all development potential and all forest cover allocation are also transferred in the covenant document;

(C) At least 3,000 square feet of EIA credit shall be retained for every property or sending site proposing to transfer EIA credits unless the property owner voluntarily waives all development potential and designates the entire site as nonbuildable.

(2) EIA credits may be transferred from sending properties containing existing development in the form of square feet of EIA allocation, provided the following are met:

(A) The EIA allocation of the sending property as a whole shall be calculated, and the amount utilized by existing development, the amount to be retained for future development, and the amount to be transferred to the receiving property shall be clearly described. If existing development exceeds allocated EIA, specific facilities to achieve a specific proposed level of EIA shall be constructed and successfully operated for three years prior to approval of any transfer to demonstrate compliance with the EIA levels proposed;

(B) The future development limitations proposed for the sending property including the specific number of future units shall be described, total impervious surface shall be designated, and feasibility of meeting EIA standards shall be demonstrated with the nontransferred allocation within the covenant document;

(3) EIA credits may be transferred only from a property that meets all criteria of forest cover, described in subsection (B)(3) of this section, or includes provisions for forest rehabilitation or reestablishment.

(4) Detention and treatment must be provided for each site in accordance with the LID Supplement to the Bothell Design and Construction Standards and the Bothell Surface Water Design Manual; detention and treatment facilities must be sized for all of the EIA on a site.

(5) A covenant document shall be filed and recorded with the Snohomish County auditor on the sending property indicating that the credits have been transferred and may not be used in the future to support development of additional areas of impervious surface.

c. A management plan shall accompany all proposals for facilities to meet the effective impervious surfaces standards addressing:

(1) Ownership of facilities, which may include:

(A) Private ownership and management of facilities on individual lots or parcels that do not serve public roads or other public facilities and are of a nature that maintenance can most effectively be provided by a homeowner or association. A management manual or guidelines may be required to be prepared by the applicant and shall be filed with the city in order to assure that it is available to the future landowner. Any such facilities shall be identified by a recorded easement or plat restriction that provides:

(1) The location and function of the facility;

(2) A list of required management activities, or reference to a management manual that may be recorded separately and referenced;

(3) The right of the city to enforce the terms of the restriction, including the right to require alteration of the facility if it does not perform according to the approved specifications.

(B) Dedication of the facility within a separate tract or within an easement containing the facility to the city for operation and maintenance. This will generally be employed when the facility serves public roads or other public facilities and is of a nature that maintenance can most effectively be provided by the city.

(2) A management plan for the facility shall include all periodic maintenance required for function according to the approved performance specifications and the Bothell Surface Water Design Manual.

(3) The city shall require a performance security in the form of a surety bond, performance bond, assignment of savings account, or an irrevocable letter of credit to assure installation, maintenance and other performance standards in accordance with the Bothell Design and Construction Standards and Specifications (Bothell Standards). Public development proposals shall be relieved from having to comply with the bonding requirements of this section if public funds have previously been committed for mitigation, maintenance, monitoring, or restoration.

d. Application of the standards for effective impervious area (EIA) shall be limited by the following:

(1) The effective impervious area standard shall not apply to arterials and collector streets, including the area of arterial right-of-way dedicated to the city as part of a private residential or commercial project; provided, that the maximum feasible reduction of surface water runoff is achieved in project design in accordance with the criteria in subsection (B)(2)(a) of this section.

(2) Existing development that exists on or before March 15, 2008, shall be governed by the provision for nonconforming uses in Chapter 12.26 BMC except for the following:

(A) A one-time expansion of impervious surface of up to 750 square feet. Expansions of more than 750 square feet shall include provision for the maximum feasible reduction of surface water runoff in accordance with the criteria in subsection (B)(2)(a) of this section.

(B) Any existing lot of record which exists on or before March 15, 2008, may be developed with one single-family residence with up to 3,000 square feet or less of total impervious surface without meeting the standard for maximum effective impervious area; provided, that development shall include provision for the maximum feasible reduction of surface water runoff in accordance with the criteria in subsection (B)(2)(a) of this section.

3. Forest Cover Requirements.

a. Forest cover on site shall not be less than 50 percent for lands zoned R 5,400a (LID). Forest cover shall be based upon the gross area of the total site and may include critical areas and critical area buffers as defined by Chapter 14.04 BMC.

b. Preservation or restoration of forested cover shall meet the following criteria in order of priority:

(1) Preservation or restoration of forest areas within critical areas or their buffers or adjacent to those buffers required for critical areas pursuant to Chapter 14.04 BMC;

(2) Preservation of existing forested areas with a relative tree density of 20 or more on soil types with the highest potential for infiltration of project surface water through gravity systems;

(3) Preservation and restoration of existing areas with a relative tree density between 10 and 20 on soil types with the highest potential for infiltration and providing the potential for dispersion of project surface water through gravity systems;

(4) Restoration of existing areas with a relative tree density of less than 10, or nonforested areas on soil types with the highest potential for infiltration and providing the potential for dispersion of project surface water through gravity systems;

(5) Preservation of existing forested areas with a relative tree density of 20 or more not meeting the criteria above;

(6) Preservation and restoration of existing areas with a relative tree density of less than 20, or nonforested areas not meeting the criteria above.

c. Facilities allowed within forest areas are limited to:

(1) Surface water dispersion systems as described in the LID Supplement to the Bothell Design Standards specifications and the Bothell Surface Water Design Manual;

(2) Recreational trails not exceeding three feet in width and not requiring more than 18 inches of cut or fill and constructed of a pervious surface consisting of wood chips or similar materials.

d. Transfer of Credit for Forest Cover. Any property within the Canyon Creek/39th Avenue SE Subarea with NCFWCHPA LID zoning may transfer credits for preservation and restoration of forest area to other sites within the NCFWCHPA LID zoning portion of the Canyon Creek/39th Avenue SE Subarea subject to the following provisions. All forest cover transfers, allocations, limitations, provisions and stipulations shall be identified within a covenant document which is reviewed and approved by the community development director. The covenant document shall be a permanent covenant running with the land in perpetuity filed and recorded with the Snohomish County auditor:

(1) Credits shall be in the form of square feet of forest area. Transfer may only be in an amount in addition to the minimum forest cover for a site provided in subsection (B)(3)(a) of this section; provided, that:

(A) Forest cover areas used for storm water dispersion or other storm water management facilities shall not be transferred.

(B) Forest cover areas with a relative tree density of 20 or greater that meet the additional criteria in the definition of forest area or cover shall be granted 100 percent credit.

(C) Forest cover areas with a relative tree density of 20 or greater that do not meet all standards for native species or understory may be granted 100 percent credit upon completion of forest restoration, with the provisions for monitoring survival and replacement.

(D) Forest cover areas with a relative tree density between 10 and 20 with completion of forest restoration shall be granted no more than 80 percent credit if the restoration was established less than three years previously or has not been monitored and met success standards after a period of three years. If forest rehabilitation has been completed and monitored for at least three years and meets standards for success, 100 percent credit may be granted.

(E) Forest cover areas with a relative tree density of less than 10 with completion of forest restoration shall be granted no more than 60 percent credit if the restoration was established less than five years previously or has not been monitored and met success standards after a period of five years. For forest cover areas in which forest restoration has been completed and monitored for at least five years and meets standards for success, 100 percent credit may be granted.

(F) Areas that are nonforested with completion of forest restoration shall be granted no more than 50 percent credit, if the restoration was established less than five years previously or has not been monitored and met success standards after a period of five years. On sites in which forest restoration has been completed and monitored for at least five years and meets standards for success, 100 percent credit may be granted.

(2) A covenant shall be filed and recorded with the Snohomish County auditor on the sending property from which forest cover credit is transferred indicating that the credits have been transferred and may not be used for future development. The specific limit to the remaining developable area shall be attached to the site as a permanent covenant to run with the land.

(3) Any land subject to transfer for forest cover credit shall provide for permanent preservation and management consistent with the requirements in subsection (B)(3)(f) of this section.

e. In order to inform subsequent purchasers of real property of the requirements for preservation or restoration of forest cover, the owner of any property subject to these requirements shall file and record a covenant document with the Snohomish County auditor on a form approved by the city that shall state the presence of forest cover requirements, the requirement for preservation of forest cover and implementation of any required restoration and enhancement, the location on a site plan of the area of required forest cover, place such forest areas into separate tracts and provide for dedications for management and that the covenant shall run with the land in perpetuity.

f. All retained and restored forest area must be accompanied by a management plan addressing:

(1) Ownership of the forest area, which may include:

(A) Private ownership and management for forest area on individual lots or parcels that are not of sufficient size and character to allow effective management by the city or other public entity. Any such forest area shall be preserved within a recorded separate tract with a plat restriction that provides:

(1) An assurance that native vegetation will be preserved or restored to meet the criteria of this chapter; and

(2) The right of the city to enforce the terms of the restriction.

(B) Private ownership by an individual lot owner, undivided interest by each owner of a building lot within the development with the ownership interest passing with the ownership of the lot, or held by an incorporated homeowners’ association within a separate tract with a plat condition providing for management by a public entity when the city determines that:

(1) The forest area is of sufficient size and character to allow effective management by the city or other public entity; or

(2) The forest area contains critical areas that are best managed by a public entity in conformance with criteria in BMC 14.04.290.

(C) Dedication of a separate tract containing the forest area to the city, another public agency, or conveyance to a legal entity such as an incorporated land trust, which ensures the ownership, protection and maintenance, and protection of the forest cover.

(2) A management plan for the forest cover area shall include:

(A) Marking of the boundaries of the area, which includes open rail fencing to provide for ready field identification and prevent encroachment upon the area and signage which shall describe the purpose of the forest area and identify ownership and which shall be placed no more than 100 feet apart around the entire forest area boundary;

(B) Provisions for installation and monitoring of any required restoration and enhancement plantings, including monitoring of the survival of plantings for a five-year or longer period where dead or dying plants shall be replaced as needed;

(D) Management of any storm water management facilities allowed within the area;

(E) The city shall require a performance security in the form of a surety bond, performance bond, assignment of savings account, or an irrevocable letter of credit to assure installation, maintenance and other performance standards in form and amount deemed acceptable by the city in the amount of 125 percent of the estimated cost of the performance that shall remain in effect until the city determines, in writing, that the requirements have been met. Bonds or other security shall be held by the city for a minimum of three years and may be held for longer periods when deemed necessary by the community development director. Public development proposals shall be relieved from having to comply with the bonding requirements of this section if public funds have previously been committed for mitigation, maintenance, monitoring, or restoration.

g. Application of forest cover requirements shall be limited by the following:

(1) The forest cover standard shall not apply to arterials and collector streets, including the area of arterial right-of-way dedicated as part of a private residential or commercial project;

(2) Existing development shall be governed by the provision for nonconforming uses in Chapter 12.26 BMC, except that a one-time exception may be granted for the following:

(A) Any expansion of impervious surface of more than 500 square feet shall include a requirement to provide forest cover on up to 50 percent of the lot area not covered by impervious surface.

(B) Any existing lot of record which exists on or before March 15, 2008, may be developed with one single-family residence with an allowance of up to a total of 3,500 square feet of nonforest cover.

4. Site Design Regulations. Site design shall follow a procedure to include: a site assessment to identify and describe the natural processes existing on and around the development site; design, lay out and arrange site improvements in a manner that preserves natural processes to the maximum extent feasible; and design infrastructure improvements in a manner that includes integrated storm water management.

a. The site assessment evaluation shall identify:

(1) Topography and natural runoff patterns;

(2) Soil type and infiltration potential;

(3) Vegetation cover, including type, density and ability to intercept, retain and retard surface water movement;

(4) Streams and overland water flow patterns;

(5) Wetlands and other critical areas.

b. Site design shall locate all land alteration on the least sensitive portions of the site, and cluster developed areas to achieve the following:

(1) Preservation or restoration of forest areas;

(2) Preservation and buffering of critical areas as provided in Chapter 14.04 BMC;

(3) Preservation of existing patterns of overland water flow and patterns of groundwater interflow;

(4) Preservation or restoration of patterns of wildlife movement.

c. Vehicle and pedestrian circulation systems shall be designed to minimize alteration of topography and natural hydrologic features and processes through:

(1) Roads, walkways and parking areas shall be designed to follow natural contours, avoid changes to the existing flow patterns of surface water, and maintain consolidated areas of natural topography and vegetation. Vehicle access shall be located in the least sensitive area of the site to the maximum extent feasible;

(2) Road location and circulation patterns shall reduce or eliminate stream crossings and encroachment on critical areas and their buffers;

(3) Graded slopes and alteration of vegetation cover shall be avoided by road placement, and through use of retaining walls which allow the maintenance of existing natural slope areas and shall be preferred over graded artificial slopes;

(4) Utilities shall be located within roadway and driveway corridors and rights-of-way to the maximum extent feasible to avoid additional clearing for multiple corridors.

d. Layout of lots or structures shall:

(1) Avoid portions of the site that provide for important hydrologic and critical area functions;

(2) Minimize access roadway or driveway length and area and use common access drives.

e. Design of structures and improvements shall minimize alteration of existing topography, minimize disturbance to soils and native vegetation, and provide for water infiltration and interflow.

(1) Excavation shall be prohibited from intruding into that part of the groundwater table which experiences saturated soil conditions, as measured during the dry season.

(2) Building location and design shall allow the maintenance of existing topography through:

(A) Use of pole- or pin-type construction which conforms to the existing topography is preferred.

(B) Structures shall be tiered to conform to existing topography and to minimize topographic modification. Piled deck support structures are preferable for parking or garages to fill-based construction types.

(C) Use of foundation walls as retaining walls is preferable to rock or concrete walls built separately and away from the building. Freestanding retaining devices are only permitted when they cannot be designed as structural elements of the building foundation.

(D) Standard prepared building pads (slab on grade) resulting in grading more than five feet outside the building footprint area or more than three feet of topographic modification are prohibited.

(3) Under-structure parking and multilevel structures shall be incorporated where feasible.

(4) Retaining walls and exposed foundations more than three feet in height shall be screened by vegetation.

C. Modification of Development Regulations.

1. To accommodate low impact development, the community development director is authorized to modify Chapters 12.14, 12.18, and 12.20 BMC, as specifically described below, without the need for a variance as provided for in Chapter 12.36 BMC. The city of Bothell shall decline to approve modifications in cases where conflicts occur with the Imagine Bothell... Comprehensive Plan and Fitzgerald/35th Avenue SE Subarea plan policies or if the public health, safety and welfare would not be furthered by the proposed modification.

a. BMC 12.14.030(A) may be modified pursuant to the following:

(1) Within the R 5,400a (LID) zoning classification, the minimum lot area per single-family dwelling unit may be reduced by as much as 40 percent. For example, properties with a zoning classification of R 5,400a (LID) may have a minimum lot area of 3,250 square feet.

(2) Within the R 5,400a (LID) zoning classification, minimum lot circle diameter may be reduced by as much as 20 percent. For example, properties with a zoning classification of R 5,400a (LID) may have a minimum lot circle diameter of 40 feet.

(3) Lots which are modified under subsections (C)(1)(a)(1) and (2) of this section shall provide for a special setback of 25 feet along common property lines whenever such lots are located within 50 feet of an existing primary single-family building.

b. Parking lot landscaping location and dimensional requirements in BMC 12.18.090 may be modified by the community development director to consolidate parking lot landscaping areas to allow landscape areas to function as dispersion or bioretention facilities. The required perimeter landscaping and the amount of internal parking lot landscaping shall not be varied by this provision.

c. In addition to the circumstances within BMC 12.18.160 where the community development director may grant modification to the required landscape standards of Chapter 12.18 BMC, the community development director may also grant modification to accommodate dispersion and bioretention facilities within required landscape areas. All landscape areas shall be graded to provide for water retention where feasible. Except as accessory to single-family dwellings, turf shall be discouraged and limited to recreation or community gathering areas.

d. Recreation area standards of Chapter 12.20 BMC which are applicable to the R 5,400a (LID) zone may be varied according to the following:

(1) The minimum recreation area required in BMC 12.20.020 may be modified by the community development director when trails and viewing platforms or facilities of a similar nature are provided within or adjacent to retained forest areas.

(2) Single purpose facilities may account for up to 80 percent of the required recreation area.

(3) Location, layout and dimensions of required recreation areas in BMC 12.20.040 may be varied to accommodate the use of trails and other linear facilities located within forest retention areas.

2. To accommodate low impact development the public works director, in consultation with the fire marshal, is authorized to modify the Bothell Design and Construction Standards and Specifications (Bothell Standards) as adopted in BMC 17.02.010 as specifically described below without the need for a variance as provided for in Chapters 17.23 and 18.08 BMC.

a. Bothell Design and Construction Standards.

(1) Public street width standards may be reduced pursuant to the following:

(A) Streets classified by the city as public local access streets (ADT less than 500) will be allowed to be constructed as two-lane, two-way, 20-foot-wide clear, drivable surface constructed of a standard paving material; provided, that a prohibition for on-street parking is provided on both sides of the street with appropriate signage.

(B) Should on-street parking on one side of the street be desired, a six-foot-wide parking area will be added to the 20-foot-wide drivable surface for a total width of 26 feet. The six-foot-wide parking area may be constructed of a pervious material as approved by the public works director.

(C) Should on-street parking on both sides of the street be desired, a six-foot-wide parking area will be added to both sides of the 20-foot-wide drivable surface for a total width of 32 feet. The six-foot-wide parking area may be constructed of a pervious material as approved by the public works director.

(D) Local access streets (ADT less than 500) may be allowed to be constructed as one-way looped road sections under the direction of the public works director and the city fire marshal.

(E) Guest parking must be provided when on-street parking is not constructed. One guest parking stall shall be provided for every four dwelling units. All guest parking will be clearly identified with signage and striping.

(2) Private street and fire department access drives may be reduced to the following:

(A) Local access streets (ADT less than 500) will be allowed to be constructed as a 16-foot-wide clear, drivable surface constructed of standard pavement materials, with an additional three-foot pervious material shoulder capable of supporting the imposed weight of a fire apparatus on each side; provided, that a prohibition for on-street parking is provided on both sides of the street with appropriate signage.

(B) Guest parking must be provided when on-street parking is not constructed. One guest parking stall shall be provided for every four dwelling units. All guest parking will be clearly identified with signage and striping.

b. Roadway materials standards may be varied according to the following:

(1) Pervious pavement may be allowed on road shoulders subject to specific standards established by the public works department to ensure serviceability and durability.

(2) Pervious pavement on emergency vehicle turnouts and traveled ways may be allowed on a case-by-case basis by the public works director in consultation with the fire marshal based on specific plans and information regarding roadway serviceability and durability.

c. Cul-de-sac and turn-around dimensions may be varied to provide a hammerhead type of design to reduce impervious surface and may be constructed of pervious pavement pursuant to the Bothell Design and Construction Standards.

d. Pedestrian facility placement, design, and materials standards may be varied according to the following:

(1) A single sidewalk or trail on one side of the street may be allowed on public roads and private roads and driveways if the following criteria are met:

(A) The sidewalk is not designated as a primary pedestrian access route to schools;

(B) The sidewalk does not serve more than 100 dwelling units as the single point of pedestrian access between the residential unit and other elements of the pedestrian circulation system;

(C) Marked crosswalks are provided to allow pedestrians to safely cross the street to the pedestrian facility at safe locations.

(2) Pedestrian facilities may utilize pervious pavement subject to specific standards to ensure serviceability and durability.

e. Parking lot standards may be varied to allow pervious pavement throughout the parking lot, provided drive aisles are capable of supporting the weight of fire apparatus. Pervious pavement shall be required on all portions of the parking lot other than the drive aisle when soil conditions warrant.

D. Supplemental Low Impact Storm Drainage Standards. The public works director may allow variation in the Bothell Design and Construction Standards and Specifications (Bothell Standards) as provided for in BMC 17.02.010 to accommodate low impact development as provided below:

1. Application of Standards.

a. Stormwater Manual. Within the areas identified for LID development within the Canyon Creek/39th Avenue SE Subarea, the city of Bothell shall require the use of the LID Supplement to the Bothell Design and Construction Standards and the Bothell Surface Water Design Manual for estimating surface runoff and sizing storm water control and treatment facilities.

b. Supplemental. This section describes how various LID techniques are employed to meet effective impervious surface requirements. It must be used in conjunction with the Low Impact Development Supplement to the Bothell Design and Construction Standards and Specifications (LID Supplement) and the Bothell Surface Water Design Manual.

c. Best Available Information. The public works director may approve alternatives to these standards upon review of evidence submitted by the applicant that such modifications are equal to or better than the requirements in these regulations and meet the specific criteria in Section 1-7 of the Bothell Design and Construction Standards.

d. Best Management Practices. This section identifies six categories of low impact development (LID) best management practices (BMPs) that may be used in defining specific credits for determining effective impervious surfaces and required storm water control facilities. Additional practices may be approved by the public works director in accordance with subsection (D)(1)(c) of this section.

(1) Porous asphalt and pavement;

(2) Permeable pavers;

(3) Dispersion;

(4) Vegetated roofs;

(5) Reverse slope sidewalks;

(6) Bioretention.

For each category, the basic design criteria and the amount of credit received for reduced effective impervious area are provided in the LID Supplement to the Bothell Design and Construction Standards. It is likely that more than one LID technique will be used on a site.

e. Notice, Ownership and Management. In order to inform subsequent purchasers of real property of the requirements for low impact development, the owner of any property subject to these requirements shall file and record a covenant document with the Snohomish County auditor, according to the direction of the city, that shall address the following:

(1) Designation of Easements or Tracts. All storm water management facilities shall be designated on a site plan filed for record with the surveyed boundaries and legal descriptions of storm water facilities. The owner shall dedicate either easements or tracts to the city of Bothell, as specified by the public works director, for long-term operation and maintenance of storm water management facilities.

(2) Responsibilities for management of ornamental vegetation or other features within the storm water management facilities shall be specified, together with the provision that if owners do not adequately manage such vegetation, the city may provide written notice to the landowner to remove, modify and replace vegetation within 30 days. Should the landowner fail to comply with the stipulations of the written notice, the city may complete the work at the expense of the landowner.

f. The city shall require a performance security to assure facilities meet the standards for achieving effective impervious surface standards as provided for in Section 1.5 of the Bothell Design and Construction Standards.

2. Specific Best Management Practices.

a. Porous Asphalt and Pavement. Porous asphalt can be used on private streets and on nontraveled portions of local access public streets and on driveways, street shoulders, sidewalks, parking lots and other facilities as determined appropriate by the public works director. The specific design criteria and associated credit toward reduced impervious surface area are found in the LID Supplement to the Bothell Design and Construction Standards and the Bothell Surface Water Design Manual.

b. Permeable Pavers. Permeable pavers include grid/lattice systems (nonconcrete) and paving blocks. Permeable pavers may be used on portions of local public and private streets and driveways not designated as traveled ways, such as street shoulders, sidewalks and parking areas, as well as for other facilities as determined by the public works director. An approved list of permeable pavers and the specific design criteria and associated credit toward reduced impervious surface area are found in the LID Supplement to the Bothell Design and Construction Standards and the Bothell Surface Water Design Manual.

c. Dispersion Into Preserved Forest. Dispersion of runoff from an impervious surface into retained forest areas may utilize several facilities subject to approval by the public works director. The LID Supplement to the Bothell Design and Construction Standards and the Bothell Surface Water Design Manual describes different methods for implementing dispersion on a site to reduce EIA and provide credits for treatment and flow control.

d. Vegetated Roofs. Vegetated roofs may be used to reduce the amount of effective impervious surface area of a roof.

(1) Vegetated roofs design criteria and associated credit toward reduced impervious surface area are specified in the LID Supplement to the Bothell Design and Construction Standards and the Bothell Surface Water Design Manual.

(2) Notice, Ownership and Management. Vegetated roofs shall be owned and maintained by the building owner. To inform subsequent purchasers of real property of the requirements for operation and maintenance, the owner of any property utilizing vegetated roofs shall file and record a notice with the Snohomish County auditor according to the direction of the city describing operation and maintenance requirements of the facility and holding the city of Bothell harmless for any liability resulting from the use of said facility.

e. Reverse Slope Sidewalks. Reverse slope sidewalks are sloped to drain away from the road and disperse runoff into adjacent vegetated areas. Several facility alternatives are addressed within the LID Supplement to the Bothell Design and Construction Standards and the Bothell Surface Water Design Manual with specific application and design criteria and credits for treatment and flow control.

f. Bioretention Areas. Bioretention areas are designed to provide areas where runoff from impervious surfaces can be infiltrated to appropriate soils. (Ord. 2053 § 3 (Exh. C), 2010).

12.50.050 Wildlife standards within the North Creek Fish and Wildlife Critical Habitat Protection Area (NCFWCHPA).

A. Designation of Wildlife Corridors.

1. All critical areas and buffers providing a continuous connection to North Creek along Cole Creek are designated a wildlife corridor and may not be varied, averaged or reduced except where specific findings are made that such variation will not compromise their function as a wildlife corridor.

2. Additional wildlife corridors are designated on the zoning map to provide additional connections between critical areas that may not be provided by contiguous buffers and to provide corridors to the rural and resource areas of unincorporated Snohomish County to the north and east.

B. Special Fish and Wildlife Habitat Study. A special study which evaluates project impacts on critical fish and wildlife habitat existing on and in the vicinity of the subject property shall be submitted as part of the application. The special study shall meet the following criteria:

1. The report shall be prepared in conformance with the general critical areas report requirements of Chapter 14.04 BMC and in addition shall address the existing and potential wildlife use of required forest cover.

2. Location of Fish and Wildlife Habitat. The study shall depict the location of all streams, floodplains, wetlands, riparian areas, forested areas and all other critical areas and associated buffers as required by Chapter 14.04 BMC on and within 300 feet of the project area.

3. Habitat Assessment. A habitat assessment shall be included as part of the special study. A habitat assessment is an investigation of the project area to evaluate the fish or wildlife species and habitats present on or near the subject property. The special study shall contain an assessment of habitats including the following site- and proposal-related information:

a. Detailed description of vegetation on and adjacent to the project area;

b. Identification of any species of local importance, priority species, or endangered, threatened, sensitive, or candidate species that have a primary association with habitat on or adjacent to the project area, and assessment of potential project impacts to the use of the site by the species;

c. A discussion of any federal, state, or local special management recommendations, including Washington Department of Fish and Wildlife habitat management recommendations, that have been developed for species or habitats located on or adjacent to the project area;

d. A detailed discussion of the direct and indirect potential impacts on habitat by the project, including potential impacts to water quality;

e. A discussion of specific measures and design features proposed by the applicant to avoid, minimize or mitigate impacts to habitat, including buffers wider than those required in Chapter 14.04 BMC, if found to be warranted;

f. A discussion of the specific storm water facilities proposed by the applicant to provide for protection of surface water and groundwater in the vicinity of the development; and

g. A discussion of ongoing management practices that will protect habitat after the project site has been developed, including proposed monitoring and maintenance.

4. Additional Information. The community development director may also require the following:

a. An evaluation by an independent qualified professional of the applicant’s analysis and the effectiveness of any proposed mitigating measures or programs, which evaluation may include any recommendations for alternative mitigating measures or programs; and

b. Consultation with the Washington Department of Fish and Wildlife or other appropriate agency.

C. Director’s Authority. The director of community development is authorized to evaluate, assess, and approve any specific measures determined by the director to be necessary to preserve or enhance fish and wildlife habitat and wildlife movement corridors on the subject property, in accordance with applicable comprehensive plan policies, pursuant to the following criteria:

1. All specific habitat-related measures proposed in the special study shall be based upon documented best available science for the specific type of habitat and plant and animal species located on the subject property;

2. The habitat-related measures proposed in the special study are consistent with guidance and recommendations of the State of Washington Department of Fish and Wildlife;

3. The habitat-related measures proposed are consistent with applicable Imagine Bothell... Comprehensive Plan policies;

4. Stream and wetland critical area buffers may be required to be wider than required under Chapter 14.04 BMC if such wider buffers are found to be warranted based on best available science; no reductions of stream or wetland critical area buffer widths as established under Chapter 14.04 BMC shall be permitted, except in circumstances of reasonable use;

5. Uses shall be consistent with Chapter 12.06 BMC;

6. The proposed habitat-related measures do not modify the area, dimension and design standards of Chapter 12.14 BMC; and

7. The director may require modifications to the development layout, design, location of buildings or other improvements to ensure consistency with best available science and/or to protect the fish and wildlife habitat present on the subject property. (Ord. 2053 § 3 (Exh. C), 2010).

12.50.060 Definitions.

“Adjacent impervious surfaces” means roofs, parking areas, and other impervious surfaces closer to each other than 100 feet apart. These shall be considered “adjacent impervious surfaces.”

“Best management practices (BMPs)” means specific practices and facilities used to control the adverse effects of alteration of the natural environment by elements of the built environment such as additional runoff from impervious surfaces.

“Dispersion” means distribution of runoff to a system that or land area that does not allow any downstream concentration of flow into a discrete channel.

“Drainage collection system” means a system for conveying, treating and detaining storm water runoff including but not limited to facilities such as catch basins, drains, swales, ponds, and outfalls.

“EIA (effective impervious area) credit” means a reduction in effective impervious area as a result of incorporation of facilities or systems that infiltrate water or precipitation such that it ceases to be surface water.

“Forest area or cover” means mature vegetation typical of a climax evergreen or mixed forest, characteristic of conditions that predated European settlement, that meet the following criteria:

1. Relative tree density of greater than 20;

2. No area of more than 1,000 square feet is outside of the dripline of an evergreen or deciduous tree;

3. No more than 10 percent of trees are nonnative;

4. Understory density of not less than 75 percent of ground coverage.

Areas not meeting the above criteria may qualify as forest area through successful implementation of forest restoration.

“Forest restoration” means the process of restoring native vegetation and soils on disturbed land with the intent of eventually achieving the forested condition. Forest restoration shall consist of:

1. Forest rehabilitation consists of interplanting of trees and understory in a forest with a relative tree density of less than 20 but greater than 10. Plantings shall consist of seedlings at not less than 300 trees per acre, with no more than 40 percent native nonconiferous trees together with understory plantings in any areas greater than 500 square feet not characterized by native understory.

2. Forest reestablishment consists of planting an area with a relative tree density of less than 10, or that has been substantially cleared or is characterized by introduced vegetation other than trees. Plantings shall consist of seedlings at not less than 600 trees per acre, with no more than 40 percent native nonconiferous trees together with understory plantings and soil enhancement meeting the standards of the LID Supplement to the Bothell Design and Construction Standards.

3. Larger specimens may be substituted for seedlings at a ratio of one gallon (two feet tall) or greater size counting for three seedlings each, and five gallons (four feet tall) or greater size counting for five seedlings each.

4. Understory shall consist of native shrubs and groundcover planted at a sufficient density to provide an immediate surface cover of at least 40 percent with 75 percent cover within three years and 100 percent cover within five years. Groundcover in areas that are substantially cleared of trees may consist of seeding.

“Impervious area, effective” means the component of impervious surface that is connected to surface water directly, or with a conveyance device (such as a ditch, pipe or retention/detention facility) and excludes the component of total impervious area (TIA) that drains into systems that infiltrate water such that it ceases to be surface water. The measure of effective impervious area requires reliable projections of the effectiveness of facilities designed to intercept and infiltrate runoff from the total impervious area.

“Impervious area, total” means the sum of all areas on a site that inhibit the infiltration of storm water and result in surface water runoff. For the purpose of low impact development, areas that produce runoff include, but are not limited to, paved areas including roads, sidewalks, driveways, parking areas, roofs, patios, concrete or asphalt paving, gravel roads, packed earthen materials and may include landscaped areas including turf that do not contain sufficiently pervious or amended soils, but not including forested areas.

“Relative tree density” is a method for evaluating the density of trees in relation to the theoretical maximum density for trees of the same size and species. Relative tree density equals the basal area of all trees in the stand divided by the square root of the quadratic mean diameter. Relative tree density shall be determined by applying the following formula: Relative Tree Density = G/QMD1/2 where G is basal area square feet/acre and QMD is the square root of the quadratic mean diameter (inches). This method is more fully explained in the publication, A Simple Index of Stand Density for Douglas-Fir, Robert O. Curtis, Forest Science, Vol. 28, No. 1, 1982, pp. 92 – 94, Copyright 1982, by the Society of American Foresters, www.treesearch.fs.fed.us/pubs and in the publication, Family Forest Habitat Conservation Plan, prepared by The Family Forest Foundation, Chehalis, Washington, December 2006, www.familyforestfoundation.org. This method is preferable to a simple density (trees/acre) calculation because it is a more accurate measure of occupied growing space and suppression mortality.

“Storm water detention” means a system that provides temporary storage and controlled release of storm water.

“Vegetated roof” means a vegetated roof carrying, and designed to carry, at least 18 inches of soil supporting plant life, built by a licensed roofing contractor meeting the criteria of the LID Supplement to the Bothell Design and Construction Standards and the Bothell Surface Water Design Manual. (Ord. 2053 § 3 (Exh. C), 2010).