Chapter 14.08
STREAMS
Sections:
14.08.010 Purpose.
14.08.020 Classification.
14.08.030 Buffers.
14.08.040 Development provisions.
14.08.050 Stream mitigation.
14.08.060 Mitigation plans for alteration to streams and stream buffers.
14.08.010 Purpose.
The purpose of the stream conservation areas is to preserve and protect those areas with which salmonid fish, threatened and endangered species, and salmonid species of local importance have a primary association. (Ord. 1243 Exh. B (part), 2006).
14.08.020 Classification.
As defined in WAC 222-16-030, maps will be updated to the following water typing system:
Type S (shorelines): All waters, within their bankfull width, as inventoried as “Shorelines of the State” (rivers over 20 cfs, marine shorelines and lakes over 20 acres) under Chapter 90.58 RCW and the rules promulgated pursuant to Chapter 90.58 RCW, including periodically inundated areas of their associated wetlands. “Bankfull width” is the measurement of the lateral extent of the water surface elevation perpendicular to the channel at bankfull depth.
Type F (fish): Segments of natural waters other than Type S waters that are within the bankfull widths of defined channels and periodically inundated areas of their associated wetlands, or within lakes, ponds, or impoundments having a surface area of one-half acre or greater at seasonal low water that in any case contain fish habitat or are described by one of the four categories in WAC 222-16-030(2).
Type Np (non-fish perennial): All segments of natural waters within the bankfull width of defined channels that are perennial non-fish habitat streams. Perennial streams are waters that do not go dry at any time during a year of normal rainfall. However, for the purpose of water typing, Type Np waters include the intermittent dry portions of the perennial channel below the uppermost point of perennial flow.
Type Ns (non-fish seasonal): All segments of natural waters within the bankfull width of the defined channels that are not Type S, F, or Np waters. These are seasonal, non-fish habitat streams in which surface flow is not present for at least some portion of a year of normal rainfall and are not located downstream from any stream reach that is a Type Np water. Ns waters must be physically connected by an aboveground channel system to Type S, F, or Np waters.
Type C (conveyance): As defined by the city of North Bend, Type C waters are those natural open ephemeral drainage courses (including where bridged, piped or culverted) that are not Type S, F, Np or Ns waters, which contain flow only during or immediately after periods of precipitation, and which flow generally less than 30 days per year.
Figure 3, River and Stream Map1, identifies rivers and streams in the North Bend vicinity. Where possible, streams will be converted according to WAC 222-16-031. Those streams that have not been classified will be typed according to the new system summarized above. The map may be periodically revised by the city to add or remove areas based on additional information. (Ord. 1354 § 1 Exh. A (part), 2009: Ord. 1243 Exh. B (part), 2006).
14.08.030 Buffers.
The following buffers are the minimum requirements for streams. All buffers shall be measured from the ordinary high water mark (OHWM).
A. Types S and F streams shall have a 100-foot buffer on each side of the channel. Seventy-five feet of this buffer shall be considered the “inner buffer” and 25 feet of this buffer shall be considered the “outer buffer.”
B. Type Np streams shall have a 50-foot buffer on each side of the channel.
C. Type Ns streams shall have a 25-foot buffer on each side of the channel.
D. Type C water shall have no buffer. (Ord. 1243 Exh. B (part), 2006).
14.08.040 Development provisions.
The requirements provided in this section supplement those identified in Chapter 14.05 NBMC. Activities may only be permitted in a stream or stream buffer if the applicant can show that the proposed activity will not degrade the functions and values of the stream, stream buffer, or other critical area.
A. Inner Buffer Development Provisions – Type S and F Streams. Activities and uses shall be prohibited in inner buffers of Type S and F streams except as provided for in Chapter 14.05 NBMC, Critical Areas – Administration, General Provisions and Definitions, and those within the range of the allowable activities and uses listed below:
1. Stream Crossings. Stream crossings shall be minimized, but when necessary they shall conform to the following standards as well as other applicable laws (see the State Department of Fish and Wildlife, or the State Department of Ecology).
a. The stream crossing is the only reasonable alternative that has the least impact;
b. It has been shown in the critical area report that the proposed crossing will not decrease the stream and associated buffer functions and values;
c. The stream crossing shall use bridges instead of pipe or box culverts unless it can be demonstrated that a pipe or box culvert would result in equal or less ecological impacts;
d. All stream crossings using pipe culverts shall use super span or oversized culverts with appropriate fish enhancement measures. Culverts shall not obstruct fish passage;
e. Stream crossings shall be designed according to the Washington Department of Fish and Wildlife Fish Passage Design at Road Culverts, 1999, and the National Marine Fisheries Service Guidelines for Salmonid Passage at Stream Crossings, 2000;
f. All stream crossings shall be constructed during the summer low flow period between June 15th and September 15th or as specified by the State Department of Fish and Wildlife in the Hydraulic Project Approval;
g. Stream crossings shall not occur through salmonid spawning areas unless no other feasible crossing site exists;
h. Bridge piers or abutments shall not be placed in either the floodway or between the ordinary high water marks unless no other feasible alternative placement exists;
i. The natural drainage pattern and discharges of the upstream drainage basin, up to the runoff event having an exceedance probability of 0.01, shall not be altered or diminished by a stream crossing;
j. Stream crossings shall minimize interruption of downstream movement of wood and gravel;
k. Stream crossings shall be designed to facilitate routine maintenance of culverts and bridges; and
l. Stream crossings shall be minimized by serving multiple properties when-ever possible.
2. Trails. The criteria for alignment, construction, and maintenance of trails within wetlands and their buffers shall apply to trails within stream buffers. Fishing platforms or docks shall be included in the list of permitted trail improvements for streams, subject to shoreline regulations.
3. Utilities. The criteria for alignment, construction, and maintenance within the wetland buffers shall apply to utility corridors within stream buffers. In addition, corridors shall not be aligned parallel with any stream channel unless the corridor is outside the buffer, and crossings shall be minimized. Installation shall be accomplished by boring beneath the scour depth and hyporheic zone of the water body where feasible. Crossings shall be contained within the existing footprint of an existing or new road or utility crossing where possible. Otherwise, crossings shall be at an angle greater than 60 degrees to the centerline of the channel. The criteria for stream crossing shall also apply.
4. Stormwater conveyance facilities; provided, that they are only located in the buffer when no practicable alternative exists outside the buffer. Stormwater facilities shall be planted with native plantings where feasible to provide habitat, and/or less intrusive facilities should be used.
5. Floodway-Dependent Structures. Floodway-dependent structures or installations may be permitted within streams or their buffers if allowed or approved by other ordinances or other agencies with jurisdiction. See NBMC 14.12.030 for more information on allowed uses and activities within flood hazard areas.
6. Septic Systems. New septic systems are prohibited in the inner stream buffers.
7. Stream bank stabilization shall only be allowed when it is shown, through a stream bank stability assessment conducted by a qualified fluvial geomorphologist or hydraulic engineer, that such stabilization is required for public safety reasons, that no other less intrusive actions are possible, and that the stabilization will not degrade instream or downstream channel stability. Stream bank stabilization shall utilize bioengineering or soft armoring techniques unless otherwise demonstrated. Stream bank stabilization shall conform to the Integrated Streambank Protection Guidelines developed by the Washington State Department of Fish and Wildlife, 2002, or as revised. Stabilization measures must demonstrate the following:
a. Natural shoreline processes will be maintained. The project will not result in increased erosion or alterations to, or loss of, shoreline substrate within one-quarter mile of the project area;
b. The stabilization measures will not degrade fish or wildlife habitat conservation areas or associated wetlands; and
c. Adequate mitigation measures ensure that there is no net loss of the functions or values of riparian habitat.
8. Maintenance, repair, or replacement of lawfully established existing bank stabilization is allowed, provided it does not increase the height or linear amount of bank and does not expand waterward or into aquatic habitat landward.
B. Outer Buffer Development Provisions – Type S and F Streams. Activities and uses shall be prohibited in outer buffers of Type S and F streams except as provided for in Chapter 14.05 NBMC, Critical Areas – Administration, General Provisions and Definitions, and those within the range of the allowable activities and uses listed below.
1. Trails. The criteria for alignment, construction, and maintenance of trails within wetlands and their buffers shall apply to trails within stream buffers. Outer buffer trails may not exceed 10 feet in width and may be constructed with impermeable surface materials if on-site infiltration is utilized.
2. Utilities. The criteria for alignment, construction, and maintenance within the wetland buffers shall apply to utility corridors within stream buffers. In addition, corridors shall not be aligned parallel with any stream channel unless the corridor is outside the buffer, and crossings shall be minimized. Installation shall be accomplished by boring beneath the scour depth and hyporheic zone of the water body where feasible. Crossings shall be contained within the existing footprint of an existing or new road or utility crossing where possible. Otherwise, crossings shall be at an angle greater than 60 degrees to the centerline of the channel. The criteria for stream crossings shall also apply.
3. Stormwater Conveyance Facilities. Detention/retention ponds shall not be located in the buffer unless they are designed to retain water at all seasons of the year.
4. Septic Systems. New septic systems may occur in the outer stream buffers if the proponent has demonstrated to the satisfaction of the city that there is no feasible alternative. The septic system must meet vegetation retention and site clearing limits, and be accessory to development otherwise allowed by regulation. Repairs to septic systems should be accomplished by the least impacting method (connection to sanitary sewer, replacement with new system located outside the buffer, or repairs to existing system).
5. Passive recreation facilities may be permitted in the outer buffer area and include, but are not limited to, benches, fitness trails, interpretive signage, and similar uses.
6. Native vegetation landscaping schemes that do not require application of herbicides, pesticides, or fertilizer to maintain robust growth.
7. No net effective impervious surfaces may be created in the outer buffer area, beyond what is otherwise permitted.
8. No structures or related improvements including buildings, docks, or decks shall be permitted within the stream buffer except as otherwise allowed in Chapter 14.05 NBMC or required under the city’s shoreline master program.
C. Type Np and Ns Streams. Activities and uses that result in unavoidable and necessary impacts may be permitted in Type Np and Ns streams and buffers in accordance with an approved critical area report and mitigation plan, and only if the proposed activity is the only reasonable alternative that will accomplish the applicant’s objectives.
D. Type C Waters. Type C waters are regulated for the values they provide for conveyance, infiltration, water quality treatment, and flow attenuation of surface waters. It is encouraged that Type C waters be maintained in their existing natural channels to provide these functions. However, subject to conformance to all floodplain management regulations, such channel courses may be altered, piped or realigned, so long as sufficient mitigation is provided that maintains:
1. One-hundred-year conveyance capacity;
2. Infiltration capacity equivalent to that provided by the original channel either within the altered, piped or realigned system or together with other infiltration accomplished elsewhere on the site; and
3. Comparable water quality treatment per the King County Surface Water Design Manual (as now in effect or subsequently amended) either within the altered, piped or realigned system or together with other above ground water quality measures provided for the on-site development that are accomplished elsewhere on the site. (Ord. 1354 § 1 Exh. A (part), 2009: Ord. 1243 Exh. B (part), 2006).
14.08.050 Stream mitigation.
No net loss of stream functions and values shall occur as a result of the overall project. The mitigation requirements for stream alterations, in addition to the requirements in Chapter 14.05 NBMC, shall meet the following minimum performance standards and shall occur pursuant to an approved mitigation plan:
A. Achieve equivalent or greater functions, including, but not limited to habitat functions and hydrologic functions.
B. Maintain or improve stream channel dimensions, including depth, length, and gradient.
C. Restore disturbed stream buffer areas with native vegetation.
D. Create an equivalent or improved channel bed.
E. Create equivalent or improved biofiltration.
F. Replace disturbed stream and stream buffer habitat features and areas.
G. Unless it is demonstrated that a higher level of stream function would result from an alternate mitigation approach, compensatory mitigation should be either in-kind and on-site, or in-kind and within the same stream reach or drainage subbasin of the stream. Mitigation actions should be conducted on-site and within the drainage subbasin of the affected stream, except when:
1. There are no reasonable on-site or drainage subbasin opportunities in the affected stream with a high likelihood of success;
2. Off-site mitigation has a greater likelihood of providing equal or improved functions; and
3. Established watershed goals for water quality, flood, conveyance, habitat, or other functions, including priorities and recommendations outlined in the WRIA 7 Salmon Conservation Plan, justify location of mitigation at another site.
H. For temporary alterations to a stream buffer permitted by administrative exception (NBMC 14.05.085(A)) alteration, repair, rehabilitation, or restoration must be on-site at a 1:1 ratio of area of mitigation to area of alteration.
I. Restoration or enhancement including illegal alterations must attain the following ratios of area of mitigation to area of alteration:
1. For mitigation on-site:
a. Two-to-one ratio for a Type S or F stream; and
b. One-and-one-half to one ratio for a Type N stream.
2. For mitigation off-site:
a. Three-to-one ratio for a Type S or F stream; and
b. Two-to-one ratio for a Type N stream.
J. “On-site mitigation” means within the same drainage subbasin of the stream as the alteration site and within one-half mile upstream or downstream.
K. “Off-site mitigation” means within the same drainage subbasin of the stream as the proposed alteration site and beyond one-half mile upstream or downstream. The preferred location for off-site mitigation shall be in or adjacent to a designated fish and wildlife habitat area and shall be limited to Type Ns streams.
L. The requirements in this section may be modified at the director’s direction if the applicant demonstrates that, with respect to each stream area function, greater functions can be obtained in the affected drainage subbasin through alterative mitigation. (Ord. 1243 Exh. B (part), 2006).
14.08.060 Mitigation plans for alteration to streams and stream buffers.
The scope and content of a mitigation plan to alter stream and stream buffers shall be decided on a case-by-case basis. As the impacts to the critical area increase, the mitigation measures to offset these impacts will increase in number and complexity. Refer to provisions in Chapter 14.05 NBMC. (Ord. 1243 Exh. B (part), 2006).
See city website for current version.