30.62A.320 Standards and requirements for buffers and impervious surfaces

30.62A.320 Standards and requirements for buffers and impervious surfaces.

Buffers shall be required adjacent to streams, lakes, wetlands and marine waters to protect the functions and values of these aquatic critical areas.

(1) Buffer standards and requirements - no mitigation required. All development activities, actions requiring project permits and clearing that comply with the buffer requirements of subsections (1)(a) through (g) of this section satisfy the avoidance criteria of SCC 30.62A.310(3) and are not required to provide mitigation.

(a) Buffer widths shall be as set forth in Table 2a or 2b below

Table 2a Stream, Lake and Marine Buffer Width Standards (Feet)
Streams and Lakes
Type S		150
Type F with anadromous or resident salmonids		150
Type F without anadromous or resident salmonids		100
Type Np		50
Type Ns		50

Marine Waters
Type 1	All marine waters	150

Table 2b Wetland Buffer Width Standards (feet)
Wetlands
Wetland Category	Description	Buffer Width Requirements (feet)
		Standard Buffer Width**	High Intensity Land Use ¹ [30.62A.340(4)(c)]			Low Intensity Land Use ²
		Standard Buffer Width**	Buffer w/out mitigation measure 1 or 2	Buffer w/ mitigation measure 1 (*may use measure 1 OR 2)	Buffer w/ mitigation measures 1 AND 2	Low Intensity Land Use ²
Wetlands containing salmonids (minimum)		150
Category I	Wetlands listed by the Washington Natural Heritage Program as having High Conservation Value	190	250	220*	190	125
	Bogs	190	250	220*	190	125
	Estuarine wetlands (greater than or equal to one acre) & Coastal Lagoons (greater than or equal to 1/10 acre)	150	200	175*	150	100
	High level habitat function (habitat function score is 8-9)	225	300	262*	225	150
	Moderate level habitat function (habitat function score is 5-7)	110	150	130*	110	75
	Total score 23 or above but not meeting above criteria	75	100	75		50
Category II	Estuarine wetlands (less than 1 acre)	110	150	130*	110	75
	High level of function for habitat (habitat function score is 8-9)	225	300	262*	225	150
	Moderate to high level of function for habitat (habitat function score is 5-7)	110	150	130*	110	75
	High level of function for water quality improvement and low for habitat (water quality function score is 8-9 and habitat function score is less than 5)	75	100	75		50
	Total score 20-22 but not meeting above criteria	75	100	75		50
Category III	Moderate level habitat function (habitat function score is 5-7)	110	150	110		75
Category III	Total score of 16-19 but not meeting above criteria	60	80	60		40
Category IV	Low level function score (less than 16)	40	50	40		25

1High intensity land uses include:

• commercial or industrial uses

• nonresidential use in zones where the primary intent is residential use as per SCC 30.21.025

• Residential use (4 or more units/acre)

• High-intensity recreation (golf courses, ball fields, ORV parks, etc.)

2Low intensity land uses include:

• Forestry (cutting of trees only)

• Low-intensity open space (hiking, bird-watching, preservation of natural resources, etc.)

• Unpaved trails

• Utility corridor without a maintenance road and little or no vegetation management.

**Standard buffers represent moderate level land use intensity and include uses that are not defined as high or low intensity.

(b) Buffer widths shall be measured as follows:

(i) the buffer for streams, lakes and marine waters shall be measured from the ordinary high-water mark extending horizontally in a landward direction and for wetlands, the buffer shall be measured from the edge of the wetland extending horizontally in a landward direction; and

(ii) provided however, where the landward edge of the standard buffer shown in Table 2a or 2b extends on to a slope of 33 percent or greater, the buffer shall extend to a point 25 feet beyond the top of the slope.

(i) no new effective impervious surfaces are allowed within the buffer of streams, wetlands, lakes or marine waters; and

(ii) total new effective impervious surfaces shall be limited to 10 percent within 300 feet of:

(A) any streams or lakes containing salmonids;

(B) wetlands containing salmonids; or

(d) All development activities, actions requiring project permits or clearing shall be designed to avoid the loss of or damage to trees in buffers due to blow down or other causes.

(e) All development activities, actions requiring project permits or clearing shall be sited and designed to prevent the need for shoreline or bank stabilization and structural flood hazard protection measures for the life of the development except as allowed pursuant to SCC 30.62A.330(2)(b).

(f) The following measures for reducing buffer width and area may be used without a critical area study or mitigation plan:

(i) separate tract reductions. Up to a 15 percent reduction of the standard buffer is allowed when the buffer and associated aquatic critical area are located in a separate tract as specified in SCC 30.62A.160(3);

(ii) fencing reductions. Up to a 15 percent reduction of the standard buffer is allowed when a fence is installed along the perimeter of the buffer. The fence shall be designed and constructed as set forth below:

(A) the fence shall be designed and constructed to be a permanent structure;

(B) the fence shall be designed and constructed to clearly demarcate the buffer from the developed portion of the site and to limit access of landscaping equipment, vehicles, or other human disturbances;

(C) the fence shall allow for the passage of wildlife, with a minimum gap of one and one half feet at the bottom of the fence, and a maximum height of three and one half feet at the top; and

(D) the enhancement area complies with the enhancement ratios of Table 3; and

(iii) for permanent fencing combined with separate tracts, the maximum reduction shall be limited to 25 percent.

(g) The following buffer reduction methods are only allowed in conjunction with a critical area study, pursuant to SCC 30.62A.140, demonstrating that the methods will provide protection equivalent to the standard requirements contained in Tables 2a and 2b:

(i) the width of a buffer may be averaged, by reducing the width of a portion of the buffer and increasing the width of another portion of the same buffer, if all of the following requirements are met:

(A) averaging will not diminish the functions and values of the wetland(s), fish and wildlife habitat conservation area(s) or buffer(s);

(B) the total area of the buffer on the subject property may not be less than the area that would have been required if averaging had not occurred;

(C) the total area of buffer averaging shall be placed between the developed area and the wetland, lake, stream or marine water;

(D) no part of the width of the buffer may be less than 50 percent of the standard required width or 25 feet, whichever is greater;

(E) averaging of a buffer shall not be allowed where the reduction extends into associated sloping areas of 33 percent or greater; and

(F) buffers on isolated - wetlands or lakes located in close proximity to other aquatic critical areas shall be connected by corridors of native vegetation where possible using the buffer averaging provisions of this section and the following criteria:

(1) the width of the corridor connection between the aquatic critical areas shall be no less than the combined average of the standard buffers for each of the critical areas, provided that if there is not sufficient buffer area available when using averaging to establish a connection, a connection is not required;

(2) no more than 25 percent of the buffer of the individual critical areas shall be used to make a corridor connection;

(3) the corridor connection shall be established where feasible using the highest quality habitat existing between the critical areas;

(ii) enhancement reductions. Up to a 25 percent reduction of the standard buffer width and area is allowed provided the project proponent demonstrates the enhancement complies with all of the following criteria:

(A) a comparative analysis of buffer functions and values prior to and after enhancement, demonstrates that there is no net loss of buffer functions and values;

(B) a full enhancement reduction shall only be allowed where it can be demonstrated that the existing buffer functions and values are non-existent or significantly degraded. Buffers with partial function may receive a partial or prorated reduction; and

(iii) reductions may be combined based on the following criteria:

(A) for enhancement combined with permanent fencing, the maximum reduction in width and area shall be limited to 30 percent; and

(B) for enhancement combined with separate tracts, the maximum reduction in both width and area shall be limited to 30 percent.

(h) When averaging is used in combination with any or all of the reduction methods contained in this section, the buffer shall not be reduced to less than half of the standard buffer widths contained in SCC subsection (1)(a) of this section, Tables 2a or 2b.

(2) Buffer standards and requirements - mitigation required. All actions, structures or facilities listed in this section are allowed only when they are determined to be unavoidable pursuant to SCC 30.62A.310(3) and are conducted according to the standards and requirements identified in this section. When a permit is required, an applicant must also provide a critical area study meeting the requirements of SCC 30.62A.140 and a mitigation plan meeting the requirements of SCC 30.62A.150.

(a) New utilities and transportation structures are allowed within buffers when:

(i) no other feasible alternative exists or the alternative would result in unreasonable or disproportionate costs; and

(ii) location, design and construction minimizes impacts to the buffers pursuant to SCC 30.62A.310.

(b) Stormwater detention/retention facilities are allowed pursuant to the requirements of SCC 30.63A.570.

(c) Access through buffers is allowed provided it is designed and constructed to be the minimum necessary to accommodate the use or activity.

(d) Construction of pedestrian walkways or trails in buffers is allowed when constructed with natural permeable materials and does not exceed 6 feet in width.

(e) Trimming of vegetation for purposes of providing a view corridor in a buffer is allowed provided that:

(i) trimming shall not include felling, topping, or removal of trees and be limited to hand pruning of branches and vegetation;

(ii) trimming and limbing of vegetation for the creation and maintenance of view corridors shall occur in accordance with the pruning standards of the International Society of Arboriculture (See articles published by the International Society of Arboriculture, Consumer Information Program, updated July, 2005);

(iii) trimming shall be limited to view corridors of 30 feet wide or 50 percent of the lot width, whichever is less;

(iv) no more than 30 percent of the live crown shall be removed; and

(v) the activity will not increase the risk of landslide or erosion.

(f) New shoreline and bank stabilization measures or flood protection are allowed pursuant to SCC 30.62A.330(2).

(g) Reconstruction or replacement of buildings may be allowed provided the new building does not encroach further into a critical area or its buffer than did the original building being reconstructed or replaced.

(3) Buffer standards and requirements - mitigation ratios.

(a) The mitigation ratios in Table 3 shall apply to buffer impacts and mitigation measures that exceed those allowed in subsections (1)(f)(i), (1)(f)(ii), (1)(g)(i), and (1)(g)(ii) of this section.

(b) Except as provided in subsections (3)(c) and (d) of this section, to mitigate the loss of buffer functions and values, the ratios in Table 3 shall be required. The ratios are based upon the existing type of vegetative cover and are expressed in terms of the units of mitigation area needed to replace the lost functions and values of the impacted buffer area.

(c) Enhancement shall occur in accordance with enhancement criteria contained in subsections (1)(g)(ii)(A), (B) and (C) of this section.

(d) For temporary impacts, the ratios shall be to be 1:1. Temporary impacts are those that can be restored to pre-disturbance conditions in one growing season.

Table 3 Buffer Mitigation Ratios
Existing Riparian habitat vegetation type	Creation	Enhancement ¹
Mature forest	6:1	12:1

Non-mature forest	3:1	6:1

Shrub	2:1	4:1

Non-woody vegetation	1.5:1	3:1

No vegetated cover	1:1	2:1

1enhancement of the existing buffer is allowed in lieu of creation for up to one acre of buffer loss

(Added by Amended Ord. 06-061, Aug. 1, 2007, Eff date Oct. 1, 2007; Amended by Amended Ord. 10-026, June 9, 2010, Eff date Sept. 30, 2010; Amended by Amended Ord. 15-034, Sept. 2, 2015, Eff date Nov. 1, 2015).