12.50.040 Preservation of the hydrologic cycle within the North Creek Protection Area (NCPA)

12.50.040 Preservation of the hydrologic cycle within the North Creek Protection Area (NCPA).

The North Creek Protection Area (NCPA) low impact development (LID) overlay 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 the low impact development (LID) overlay and other regulations. The Palm, Woods and Cole Creek drainage basins within the Canyon Creek/39th Avenue SE Subarea have been identified as important sources of water for North Creek, via groundwater and surface water movement, which water promotes the long-term vitality of the fisheries resources found in North Creek. 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 and Cole and North Creek drainage basins. This land use section shall be used in conjunction with 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. In the event of a conflict with another code regulation, the provision which provides the greater protection to the resource shall be applied. 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 these provisions.

B. Exceptions. The special provisions of the NCPA shall not be applied to the following activities or developments; provided, however, that all activities and developments shall fully comply with the city’s critical areas regulations of Chapter 14.04 BMC, the Bothell Design and Construction Standards, including the Bothell Surface Water Design Manual, the tree retention requirements of Chapter 12.18 BMC, and all other applicable city-wide regulations:

1. Existing development on lots of record in existence on or before March 15, 2008;

2. Construction of a single-family residence on any lot of record legally established on or before March 15, 2008;

3. Short subdivisions proposing a lot area of 40,000 square feet or greater may be exempt from the special provisions of this section provided the short subdivision:

a. Creates no more than four lots;

b. Complies with the area, dimensional, setback, building coverage, hard surface coverage, building height and other standards of the city’s R 40,000 zoning classification as stipulated within Chapter 12.14 BMC;

c. Complies with all other city-wide regulations including the critical areas regulations, other applicable provisions of the zoning code, the tree retention requirements of Chapter 12.18 BMC, the latest edition of the Bothell Surface Water Design Manual and other city-wide standards; and

d. Such short subdivisions shall be exempt from the minimum lot area provisions of BMC 12.14.030(B)(2)(c).

1. Site Assessment. A site assessment shall be submitted for all developments not excepted from these provisions which identifies and describes the natural processes existing on and around the development site including:

a. Topography and natural runoff patterns;

b. Soil type and infiltration potential;

c. Vegetation cover, including type, density and ability to intercept, retain and retard surface water movement;

d. Streams and overland water flow patterns;

e. Wetlands and other critical areas;

f. Evaluation of applicable groundwater standards.

2. Special Fish and Wildlife Habitat Study. A special study which evaluates project impacts on any 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:

a. 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.

b. 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, or another dimension as approved by the director.

c. Habitat Assessment. A habitat assessment shall be included as part of the special study and shall include:

(1) Detailed description of vegetation on and adjacent to the project area;

(2) 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;

(3) 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;

(4) A detailed discussion of the direct potential impacts on habitat by the project, including potential impacts to water quality;

(5) 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;

(6) 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

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

3. 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 other agencies such as the Washington Department of Fish and Wildlife or Washington State Department of Ecology or other appropriate agencies as deemed appropriate.

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. Site design and storm water facilities shall be designed in accordance with these low impact development regulations as provided herein, and the 2016 Bothell Surface Water Design Manual.

a. Effective impervious area (EIA) shall not exceed 20 percent. EIA shall be based upon the gross area of the total site.

b. Within the NCPA, the director of public works shall specify the following forest equivalent storm water facilities in order of preference:

(1) Dispersion into intact forest areas;

(2) Bioretention.

For situations where bioretention or dispersion are determined to be unfeasible due to site conditions allowable storm water facilities may be, in order of preference:

(1) Infiltration;

(2) Other approved LID measures, provided the applicant demonstrates that such measures meet the forest equivalency performance standard stated in the Bothell Surface Water Design Manual;

(3) A combination of infiltration and/or other approved LID measures to reduce the requirement for storm water detention facilities such that the combined system meets the forest equivalency performance standard stated in the Bothell Surface Water Design Manual;

(4) Forest equivalent storm water detention.

These special storm water treatment requirements shall be applied to the entire subject property or site and shall not be limited to the developable area, or actually developed area of the subject site.

c. A maintenance/management plan addressing the proposed surface water facilities consistent with the Bothell Standards and BMC Title 18 shall accompany all proposals.

d. Application of the 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 any 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 2016 Bothell Surface Water Manual, as amended.

(2) The effective impervious surface area standard shall not apply to existing development, lots of record in existence on or before March 15, 2008, and other development activities as identified in subsection B of this section.

a. Within lands zoned R 5,400a (LID), an area equal to 50 percent of the gross site area shall be preserved as permanent forest cover. Areas allowed to be credited as forest cover include:

(1) Those portions of the site that contain intact forest lands as defined within this chapter; or

(2) Intact forest areas within critical areas and critical area buffers as defined by Chapter 14.04 BMC; provided, however, that within a critical area or a critical area buffer 100 percent of all intact forest or vegetated cover shall be preserved; or

(3) Forest rehabilitation or forest restoration lands subject to the following:

(A) Forest rehabilitation is preferred over forest restoration. Forest rehabilitation occurs on lands which contain existing stands of mature (50 or more years old) trees with or without a middle layer of plants (understory plants), where soil types are capable of infiltration or are suitable for dispersion of project surface water through gravity systems, and shall be consistent with the following:

(1) A forest rehabilitation or restoration plan prepared by a qualified expert in forestry, forest rehabilitation or restoration, landscape architecture or another field familiar with forest rehabilitation within which the expert shall make specific recommendations regarding the type of plant materials, the number of plants to be installed, any soil amendments that are needed to rehabilitate the forest, a maintenance and management plan consistent with subsection (D)(3)(d) of this section and a contingency plan to be implemented should the forest rehabilitation not meet its objectives;

(2) The forest rehabilitation plan shall be fully implemented or bonded prior to the issuance of any final occupancy permits for the subject property; or

(B) Forest restoration occurs on lands where the native trees have been removed and/or replaced for agricultural or ornamental purposes but the native soils remain in place and shall be consistent with the following:

(1) A forest restoration plan prepared by a qualified expert in forestry, forest restoration or rehabilitation, landscape architecture or another field familiar with forest restoration within which the expert shall make specific recommendations regarding the type of plant materials, the number of plants to be installed, identify soil amendments needed to rehabilitate the forest, a maintenance and management plan consistent with subsection (D)(3)(d) of this section and shall include a contingency plan to be implemented should the forest rehabilitation not meet its performance objectives;

(2) The forest restoration plan shall be implemented prior to the issuance of any final occupancy permits for the subject property; and

b. A bond equal to 120 percent of the cost of installing the forest rehabilitation or restoration plan shall be submitted to the city pursuant to BMC 12.18.170 if the applicant proposes to request occupancy of the development prior to completion of the plan.

c. Improvements 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 shall be constructed of a pervious surface consisting of wood chips, native soils, or similar materials.

d. All preserved, rehabilitated and restored forest areas 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 rehabilitation or restoration 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 forest area;

4. Site Design Regulations. Site design shall consider the information gathered in the special site study to identify and describe the natural processes existing on and around the development site and how the site design, lay out and arrangement of site improvements preserves natural processes to the maximum extent feasible.

a. 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 or, if impacts occur, any impacts are mitigated consistent with Chapter 14.04 BMC;

(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.

b. 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.

c. 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 consistent with these regulations and the Bothell Surface Water Design Manual.

(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.

(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 15 feet outside the building footprint area or more than three feet of topographic modification are prohibited.

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

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.

(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; provided, however, that the fire marshal may stipulate the use of special fire prevention facilities such as sprinklers in buildings, special fire hydrant spacing, or other fire prevention facilities.

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 may be required on all portions of the parking lot other than the drive aisle when soil conditions warrant.

F. Supplemental Requirements Regarding the Use of Specific Types of Low Impact Storm Drainage Facilities within the NCPA. Within the NCPA, the director of public works shall specify the following forest equivalent storm water facilities in order of preference:

1. Dispersion into intact forest areas;

2. Bioretention.

For situations where bioretention or dispersion are determined to be unfeasible due to site conditions allowable storm water facilities may be, in order of preference:

1. Infiltration;

2. Other approved LID measures, provided the applicant demonstrates that such measures meet the forest equivalency performance standard stated in the Bothell Surface Water Design Manual;

3. A combination of infiltration and/or other approved LID measures to reduce the requirement for storm water detention facilities such that the combined system meets the forest equivalency performance standard stated in the Bothell Surface Water Design Manual;

4. Forest equivalent storm water detention.

These special storm water treatment requirements shall be applied to the entire subject property or site and shall not be limited to the developable area, or the actually developed area of the subject site.

G. 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:

a. 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.

b. 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 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. (Ord. 2215 § 3 (Exh. B3), 2016; Ord. 2200 § 2 (Exh. B), 2016; Res. 1332; Ord. 2163 § 2 (Exh. B-3), 2014; Ord. 2053 § 3 (Exh. C), 2010).