Chapter 14.32
STORMWATER MANAGEMENT*

Sections:

14.32.010    Policy.

14.32.020    Applicability.

14.32.030    Application requirements.

14.32.040    Stormwater Management Manual.

14.32.050    Reserved.

14.32.060    Erosion and sediment control.

14.32.070    Low-impact development (LID) techniques and facilities.

14.32.080    Stormwater conveyance.

14.32.090    County acceptance of stormwater facilities.

14.32.100    Operation and maintenance.

*    Prior legislation: Ordinances 17938 (Attch. F), O20020001, O20070003, O20070009 and O20100002 (Exh. 1).

14.32.010 Policy.

(1)    Purpose. Washington State law mandates that stormwater discharge resulting from development activities and pollution-generating activities be controlled and treated to provide available and reasonable methods of erosion control, flood control, and water quality treatment. To help protect adjacent landowners from downstream flooding, erosion, and pollution, Skagit County has adopted the following requirements for both temporary and long-term stormwater management. The purpose of this Chapter is to set out the authority, regulatory requirements, submittal requirements, and procedures for stormwater drainage design, review, approval, construction, maintenance, and management in Skagit County.

(2)    Goals of LID. The goals of low-impact development (LID) are to conserve and use existing natural site features, to integrate distributed, small-scale stormwater controls, and to help prevent measurable harm to streams, lakes, wetlands, and other natural aquatic systems from development by maintaining a more hydrologically functional landscape. This Chapter accomplishes the following goals:

(a)    Manage stormwater through a land development strategy that emphasizes conservation and use of on-site natural features integrated with engineered, small-scale hydrologic controls to mimic predevelopment hydrologic conditions;

(b)    Encourage creative and coordinated site planning, the conservation of natural conditions and features, the use of appropriate technologies and techniques, and the efficient layout of streets, utility networks and other public improvements;

(c)    Reduce hard surfaces and impervious surfaces; and

(d)    Preserve or restore native vegetation.

(3)    Authority. This Chapter is adopted pursuant to the authority granted to Skagit County in:

(a)    RCW Chapter 36.70, Planning Enabling Act;

(b)    RCW Chapter 36.70A, Growth Management Act;

(c)    RCW Chapter 90.48, Water Pollution Control.

(4)    Administration. The Administrative Official administers this Chapter and has the authority to develop and implement procedures to administer and enforce this Chapter. In all cases involving technical requirements and review, the Administrative Official should give due consideration and regard to the advice and recommendations of County technical staff. (Ord. O20150006 § 2 (Att. A))

14.32.020 Applicability.

(1)    No site development activity requiring review under this Chapter, including land clearing, grading, or other construction activity, may occur until the proposed activity has been reviewed and any required development permit has been issued. No site development activity may continue without an appropriate development permit.

(2)    SCC 14.32.030 through 14.32.080 apply to any activity within unincorporated Skagit County identified below:

(a)    “New development,” meaning land disturbing activities, including Class IV general forest practices that are conversions from timber land to other uses; structural development, including construction or installation of a building or other structure; creation of hard surfaces; and subdivision, short subdivision and binding site plans, as defined and applied in RCW Chapter 58.17. Projects meeting the definition of redevelopment are not considered new development.

(b)    “Redevelopment,” meaning, on a site that is already substantially developed (i.e., has 35 percent or more of existing hard surface coverage), the creation or addition of hard surfaces; the expansion of a building footprint or addition or replacement of a structure; structural development including construction, installation or expansion of a building or other structure; replacement of hard surface that is not part of a routine maintenance activity; and land disturbing activities.

(c)    Any activity requiring a grading permit per SCC Chapter 15.04.

(3)    Exemptions. Consistent with Appendix 1, Section 1 of the County’s NPDES permit, the following activities are exempt from this Chapter:

(a)    Forest Practices. Forest practices regulated under WAC Title 222, except for Class IV general forest practices that are conversions from timber land to other uses, are exempt from the provisions of the minimum requirements.

(b)    Commercial Agriculture. Commercial agriculture practices involving production of crops or livestock as described in the County’s NPDES permit, Appendix 1, Section 1. However, the conversion from timber land to agriculture, and the construction of impervious surfaces are not exempt.

(c)    Oil and gas field activities or operations, as described in the County’s NPDES permit, Appendix 1, Section 1.

(d)    Pavement maintenance, as described in the County’s NPDES permit, Appendix 1, Section 1.

(e)    Underground Utility Projects. Underground utility projects that replace the ground surface with in-kind material or materials with similar runoff characteristics are only subject to Minimum Requirement No. 2, Construction Stormwater Pollution Prevention. (Ord. O20150006 § 2 (Att. A))

14.32.030 Application requirements.

(1)    Basic Requirement. All applications require a stormwater site plan consistent with this Section.

(a)    All stormwater site plans must include a stormwater pollution prevention plan (MR2), including provisions for erosion and sediment control.

(b)    When a stormwater site plan (MR1) is required by SCC 14.32.040, the stormwater site plan fulfills this application requirement.

(2)    Inside the NPDES Permit Area. The applicant must use the site assessment process in Chapter 2 of the Low Impact Development Technical Guidance Manual for Puget Sound (Puget Sound Partnership and WSU Extension, 2012) to develop the stormwater site plan. The site assessment provides the baseline information necessary to design strategies that preserve areas most appropriate to evaporate, transpire, and infiltrate stormwater and achieve the requirements of the Stormwater Management Manual and this chapter.

(3)    Outside the NPDES Permit Area.

(a)    A stormwater site plan must demonstrate compliance with the requirements of SCC 14.32.040.

(b)    The stormwater site plan must be prepared by a qualified professional and must include an offsite analysis only when the application includes any of the following:

(i)    Land-disturbing activity greater than or equal to one acre;

(ii)    Grading greater than or equal to 500 cubic yards;

(iii)    Any improvements within County right-of-way for which the County will ultimately assume responsibility for maintenance.

(c)    Off-Site Analysis. Any off-site analysis must be consistent with the methods described in the Stormwater Management Manual.

(d)    Geotechnical Analysis. The stormwater site plan must include a geotechnical analysis only when:

(i)    Grading or the construction of retention facilities, detention facilities, or other stormwater and drainage facilities is proposed within 200 feet of slopes steeper than 40 percent; or

(ii)    The Administrative Official deems that the proposed construction poses a potential hazard due to its proximity to a geologically hazardous area or Category I aquifer recharge area.

(e)    Soils Analysis. The stormwater site plan must include a soils analysis only when the Administrative Official deems that existing soils maps of the project site are not of sufficient resolution to allow proper engineering analysis.

(4)    Security. The County may require liability insurance and a financial security to ensure performance of the requirements of this Chapter. (Ord. O20160004 § 6 (Att. 6); Ord. O20150006 § 2 (Att. A))

14.32.040 Stormwater Management Manual.

(1)    Skagit County adopts Ecology’s 2012 Stormwater Management Manual for Western Washington, as amended in December 2014, as the Stormwater Management Manual for the entirety of unincorporated Skagit County.

(2)    Inside the NPDES Permit Area. Skagit County adopts the Thresholds, Definitions, Minimum Requirements and Exceptions, Adjustment and Variance Criteria found in Appendix I of the County’s NPDES Permit. Thresholds identified in this Chapter control only if they are lower than those required by Appendix I.

(3)    Outside the NPDES Permit Area.

(a)    Outside of the NPDES permit area, the Stormwater Management Manual’s minimum requirements are modified as provided in the table below.

Table 14.32.040-1 

Minimum Requirement (MR)

When Required, By Land Use Intensity

Low

Medium

High

MR1 Stormwater Site Plan

≥ 7,000 sq ft of new plus replaced hard surface, or

≥ 14,000 sq ft land disturbing activity

≥ 4,000 sq ft of new plus replaced hard surface, or

≥ 14,000 sq ft land disturbing activity

per manual

MR2 Construction SWPPP

always required

MR3 Source Control

not required

≥ 4,000 sq ft of new plus replaced hard surface, or

≥ 14,000 sq ft land disturbing activity

per manual

MR4 Preserve Natural Drainage

≥ 7,000 sq ft of new plus replaced hard surface, or

≥ 14,000 sq ft land disturbing activity

per manual

MR5 Onsite Stormwater Management

not required

per manual

MR6 Treatment

not required

per manual

MR7 Flow Control

not required

per manual

MR8 Wetlands Protection

≥ 7,000 sq ft of new plus replaced hard surface, or

≥ 14,000 sq ft land disturbing activity

per manual

MR9 O&M

required only if stormwater facility installed

per manual

(b)    The land use intensities in the table above have the following meanings:

Table 14.32.040-2

Land Use Intensity

Meaning

Low

Single-family residential and accessory uses on parcels of one acre or larger;

construction of agricultural buildings in Ag-NRL;

seasonal roadside stands; roads (other than those exempt as pavement maintenance)

Medium

Single-family residential and accessory uses on parcels smaller than one acre;

land divisions into four or fewer lots;

minor utility developments;

trails and trailheads

High

All other uses, including all commercial, industrial, institutional, and urban or multifamily residential uses;

land divisions into more than four lots;

all uses on parcels bisected by the NPDES Permit Area boundary;

any project that results in new plus replaced hard surface greater than or equal to 20,000 sq ft, or 1.5 acres of vegetation-to-lawn conversion, or five acres of vegetation-to-pasture conversion

(4)    Experimental Best Management Practices (BMPs). In those instances where the Stormwater Management Manual does not contain appropriate BMPs, experimental BMPs may be considered. In an effort to improve stormwater quality technology, experimental BMPs are encouraged as a means of solving problems in a manner not addressed by the Stormwater Management Manual. The Administrative Official must approve experimental BMPs and may require that the performance of experimental BMPs be monitored to document their effectiveness for future use.

(5)    Adjustments and Exceptions.

(a)    The Administrative Official may grant an adjustment to the application of the Stormwater Management Manual and its minimum requirements prior to permit approval and construction consistent with the criteria in the Stormwater Management Manual Volume I, Section 2.7 (Adjustments).

(b)    The Administrative Official may grant an exception from this Chapter or the application of the Stormwater Management Manual and its minimum requirements prior to permit approval and construction when consistent with the criteria in the Stormwater Management Manual Volume I, Section 2.8 (Exceptions/Variances). The Administrative Official must retain records, including the written findings of fact, of all exceptions from the minimum requirements.

(c)    A request for an adjustment or exception must adequately describe the justification for relief and is processed as a Level I decision under SCC 14.06.110.

(6)    Critical Drainage Areas. In order to mitigate or eliminate potential stormwater-related impacts on critical drainage areas, the Administrative Official may require additional stormwater improvements in the following areas:

(a)    All areas designated as critical areas under SCC Chapter 14.24;

(b)    All lands within 200 feet of the ordinary high water mark of waterbodies possessing fish spawning and rearing habitat for anadromous and resident fish species, as designated by the State Department of Fish and Wildlife;

(c)    Any lands that drain to a natural feature that is a closed depression, i.e., a low-lying area that has no surface outlet, or such a limited surface outlet that in most storm events, the area acts as a retention basin, holding water for infiltration, evaporation or transpiration;

(d)    Any lands that are established by law as fish or shellfish protection areas; and

(e)    Any lands determined by the Administrative Official to have a high potential for drainage and water quality problems and/or are sensitive to the effects of construction or development. (Ord. O20150006 § 2 (Att. A))

14.32.050 Reserved.

(Ord. O20150006 § 2 (Att. A))

14.32.060 Erosion and sediment control.

(1)    All development must control erosion and sedimentation during construction to permanently stabilize soil exposed during construction and to comply with the requirements of this Section. In addition to the requirements of the Stormwater Management Manual, development must do the following:

(a)    Stabilization of Exposed Soils. At all times of the year, sufficient materials, equipment, and labor must be readily available to stabilize and prevent erosion from all exposed soils and must stabilize soils before any forecasted rain event.

(b)    Delineation of Clearing and Easement Limits. Clearing limits, setbacks, buffers, and sensitive or critical areas such as steep slopes, wetlands, wellhead protection areas and riparian corridors shall be clearly marked in the field by the applicant’s surveyors or critical areas consultant and inspected by County staff (or where appropriate, by the applicant’s critical areas consultant) prior to commencement of land clearing activities.

(c)    Construction Access Routes. Wherever construction vehicle access routes intersect paved roads, provisions must be made to minimize the transport of sediment (mud) onto the paved road by use of appropriate BMPs such as a stabilized construction entrance. If sediment is transported onto a road surface, the roads must be cleaned thoroughly, as a minimum, at the end of each day. Sediment must be removed from roads by shoveling or sweeping and be transported to a controlled sediment disposal area. Street washing is allowed only after sediment is removed in this manner.

(d)    Dewatering Construction Sites. Dewatering devices must discharge into an appropriate sediment trap or pond designed to accept such a discharge, preceded by adequate energy dissipation, prior to runoff leaving the site.

(e)    Control of Pollutants Other Than Sediment. All pollutants other than sediment that occur on site during construction must be handled and legally disposed of in a manner that does not cause contamination of surface waters. Pollutants of concern include, but are not limited to, fuels, lubricants, solvents, concrete byproducts, and construction materials. (Ord. O20150006 § 2 (Att. A))

14.32.070 Low-impact development (LID) techniques and facilities.

(1)    When Allowed. To minimize the stormwater impacts of development, the low-impact development (LID) techniques and facilities identified in the Low Impact Development Technical Guidance Manual for Puget Sound (Puget Sound Partnership and WSU Extension, 2012) and this Chapter are allowed, where feasible, anywhere in unincorporated Skagit County.

(a)    Permeable pavement may be used in place of regular pavement to meet applicable LID requirements where feasible. The Administrative Official must review and approve the utilization of alternative surfacing methods for compliance with other applicable regulations and development standards.

(b)    Bioretention swales with compost-amended soils may be used, with the approval of the Administrative Official, within a right-of-way, within an easement dedicated to Skagit County adjacent to the public right-of-way, or in islands created by loop roadways.

(c)    In the event of a conflict between this Section and other development regulations, the provisions of this Section apply.

(2)    When Required.

(a)    LID techniques and facilities are required within the NPDES permit area where the NPDES permit thresholds are exceeded and where feasible. The applicant must use the BMPs identified in the Stormwater Management Manual as feasible for the site conditions. The Stormwater Management Manual provides criteria for determining feasibility of BMPs; the Administrative Official has authority to determine whether specific BMPs are feasible.

(b)    Within the NPDES permit area, projects subject to Minimum Requirements Nos. 1 to 9 in Appendix 1 of the NPDES permit must comply with the following:

(i)    After the project is complete, there may not be a net increase in impervious surface above the limit on the permit, plat, or site plan without approval from the Administrative Official.

(ii)    For subdivisions, the maximum impervious surfaces allowed for each lot must be added to the face of the plat.

(iii)    For all other development, the maximum impervious surface allowed for the development must be added to the face of the final, approved site plan.

(c)    Within the NPDES Permit Area, applicants must locate and design all buildings, streets and pathways, parking areas, and utility easements to promote public safety, ensure compatibility of uses, minimize effective impervious surface, preserve native vegetation, and complement predevelopment site characteristics such as topography, soils, hydrology, and other natural features.

(3)    General Design Techniques.

(a)    Applicants should consider limiting clearing and grading to the minimum necessary for construction of permitted uses and associated utilities.

(b)    Applicants should consider limiting lawn areas, driveways, and roads and locate them in a manner that results in the least disruption to the topography and native vegetation on the site.

(c)    Applicants should consider clustering of lots, dwelling units, or building structures during the conceptual planning stage to preserve open space, reduce total impervious surface area, and minimize development impacts on critical areas and associated buffers.

(4)    Maintenance. A maintenance plan consistent with SCC 14.32.100 is required.

(5)    Native Vegetation.

(a)    To use existing vegetation as native vegetation for stormwater dispersion, the vegetation must be characterized by a minimum of one mature evergreen or deciduous tree per 400 square feet of area. Areas not meeting this standard must be planted with the following:

(i)    Groundcover: Four-inch container plants at one per 125 square feet and native groundcover seed mix at one pound per acre;

(ii)    Understory shrubs (evergreen and/or deciduous): one-gallon plants at one per 300 square feet; and

(iii)    Canopy trees: two-gallon plants at one per 600 square feet.

(b)    The duff layer and native topsoil on a project site should be retained in an undisturbed state to the maximum extent practicable to preserve the natural stormwater holding capacity.

(c)    Where native vegetation is used to achieve Minimum Requirements 6 or 7, only the following is allowed:

(i)    Permeable pedestrian trails;

(ii)    Surface water restoration projects;

(iii)    Passive recreation;

(iv)    Removal of invasive species;

(v)    Planting of native vegetation;

(vi)    Amendment of disturbed soils consistent with all applicable regulations.

(d)    Where native vegetation is used to achieve Minimum Requirements 6 or 7, the applicant must establish one or more of the following permanent protective mechanisms to ensure that native vegetation is retained:

(i)    A protective easement dedicated to the County;

(ii)    A separate nonbuilding tract owned in common by all lots within the subdivision;

(iii)    Restrictions on the future use of the area recorded on the face of the final plat;

(iv)    An alternative permanent protective mechanism approved by the Administrative Official. (Ord. O20150006 § 2 (Att. A))

14.32.080 Stormwater conveyance.

(1)    Generally.

(a)    All proposed developments must provide on-site stormwater conveyance with sufficient capacity to convey without flooding or otherwise damaging existing or proposed structures, consistent with the Stormwater Management Manual.

(b)    Estimation of peak stormwater runoff rates used in the design of stormwater conveyance facilities must use the Rational Method, Santa Barbara Urban Hydrograph Method, Western Washington Hydrology Model, or another method, accepted by the Administrative Official, of estimating a hydrograph using a mathematical simulation.

(c)    Runoff may not discharge directly onto the surface of a public road.

(d)    Runoff and infiltration must be directed away from septic drain fields.

(e)    Runoff from impervious surfaces, roof drains, and yard drains must be directed so as not to adversely affect adjacent properties.

(f)    Runoff from development may not cause a significant adverse impact to down-gradient properties.

(2)    Easements, Tracts, and Covenants.

(a)    Drainage easements must be provided in a proposed development for all stormwater and drainage conveyance systems that are not located in public rights-of-way or tracts and must be granted to the parties responsible for providing ongoing maintenance of the systems. Drainage easements through nondrainage structures are prohibited.

(b)    Wording to this effect must appear on the face of all final plats, and must be contained in any covenants required for a development.

(3)    Wetlands. Stormwater discharges to wetlands are allowed only when consistent with the Stormwater Management Manual, especially Minimum Requirement No. 8 and Appendix I-D.

(4)    Basin Planning. A watershed-based basin plan that includes all implementing regulations and procedures (e.g., land use management adopted by ordinance for managing surface and stormwater quality and quantity management facilities and drainage features within individual sub-basins), may be used to develop requirements for source control, stormwater treatment, stream bank erosion control, wetlands, and water quality sensitive areas. A basin plan adopted by the Board of County Commissioners may be used to modify any or all of the minimum requirements for stormwater quantity or quality control addressed in this Chapter. Such modifications will be accepted; provided, that the level of protection for surface or ground water achieved by the basin plan will equal or exceed that which would otherwise be achieved by implementation of the provisions of this chapter in the absence of a basin plan. Basin plans must evaluate and include as necessary retrofitting of BMPs for existing development or redevelopment in order to achieve watershed-wide pollution-reduction goals.

(5)    Regional Facilities. When the Administrative Official has determined the public would benefit by the establishment of a regional stormwater facility that would serve as an alternative to the construction of separate on-site drainage facilities, the Administrative Official may recommend to the Board that a regional stormwater facility be constructed. This regional facility would serve more than one development in providing stormwater quantity and/or quality control. All future developments constructed on lands designated by the Board to be served by the regional facility must, at the time of issuance of any permit for a development, be required to contribute a fair share to the cost of land purchase, design, and construction of said regional facility. In the event that a proposed regional stormwater facility is not yet in operation at the time of completion of construction of a development that is to be served by said regional facility, the applicant for said development shall be required to provide temporary stormwater quantity and quality controls. Temporary quantity and quality controls may be constructed in temporary easements rather than in separate tracts. (Ord. O20150006 § 2 (Att. A))

14.32.090 County acceptance of stormwater facilities.

(1)    Skagit County may, at the Administrative Official’s sole discretion, accept stormwater facilities for maintenance. Only those that meet the following conditions will be considered for acceptance:

(a)    For residential subdivisions, improvements have been completed on at least 80 percent of the lots, unless waived by the Administrative Official;

(b)    The facility has been inspected by the County and accepted by the Administrative Official and has been in satisfactory operation for at least two years;

(c)    If the facility was reconstructed during the maintenance period, it has been accepted by the Administrative Official;

(d)    The facility as designed and constructed conforms to the provisions of this Chapter;

(e)    All easements and tracts required under this Chapter entitling the County to operate and maintain the facility have been conveyed to Skagit County and have been recorded with the Skagit County Auditor;

(f)    An operation and maintenance manual including a maintenance schedule has been submitted to and accepted by Skagit County; and

(g)    The applicant has provided to Skagit County a complete and accurate set of reproducible as-built record drawings stamped and certified as accurate by a qualified professional and accompanied by an approved maintenance plan. (Ord. O20150006 § 2 (Att. A))

14.32.100 Operation and maintenance.

(1)    Maintenance Required.

(a)    Owners and operators of stormwater facilities must operate and maintain those facilities to ensure the performance achieves their intended purposes.

(b)    Owners of property for which a stormwater BMP has been required by Skagit County must continually maintain that BMP.

(c)    Maintenance must be performed consistent with the conditions of approval and the approved maintenance plan. Unless a more restrictive provision applies, when an inspection identifies an exceedance of the maintenance standard, the owner must perform maintenance:

(i)    Within 12 months for typical maintenance of facilities, except catch basins;

(ii)    Within six months for catch basins;

(iii)    Within 24 months for maintenance that requires capital construction of less than $25,000.

(2)    Maintenance Plan Required.

(a)    Prior to the use of a stormwater facility required by this Chapter, the owner must:

(i)    Ensure a complete initial evaluation of the stormwater facility system components and property by a qualified professional to determine functionality, maintenance needs, and compliance with this Chapter and any permits. The property owner must submit the signed and stamped engineer’s evaluation to the Administrative Official for approval;

(ii)    Provide to Skagit County a complete and accurate set of reproducible as-built record drawings stamped and certified as accurate by a qualified professional;

(iii)    Obtain approval from the Administrative Official for a maintenance plan;

(iv)    Record the approved maintenance plan with the County Auditor against the title of all properties using the stormwater facility.

(b)    The maintenance plan must:

(i)    Address how all of the elements of the stormwater facility will be maintained;

(ii)    Include the schedule for ongoing maintenance;

(iii)    Identify the responsible party for ongoing maintenance;

(iv)    Be consistent with Stormwater Management Manual, especially Volume V, Chapter 4.

(c)    The maintenance plan remains in force for the life of the development or until the County approves a new or amended maintenance plan for the development’s stormwater facilities.

(d)    For LID facilities, the facility must be protected from all of the following:

(i)    Cover by structures or impervious material;

(ii)    Soil compaction, for example by vehicular traffic or livestock;

(iii)    Damage by soil removal and grade alteration;

(iv)    Conversion to another use.

(3)    Inspections of Stormwater Facilities.

(a)    Where a stormwater facility is required by this Chapter, the applicant must dedicate an easement to the County for access and inspection consistent with this Chapter and during normal business hours, and when inspectors provide advance notice. The Administrative Official may waive this requirement for small facilities that do not require inspection or can be effectively inspected without an access easement.

(b)    Inside the NPDES permit area, County inspection of stormwater facilities is required at least annually, or less frequently if allowed by the County’s NPDES permit.

(c)    Outside the NPDES permit area, the Administrative Official is authorized to develop an inspection program, including requirements for an inspection and maintenance schedule, to determine if stormwater facilities are in good working order and are properly maintained, and to ensure that stormwater BMPs are in place and that non-point source pollution control is being implemented.

(d)    Whenever there is cause to believe that a violation of this Chapter has been or is being committed, the County may inspect per SCC Chapter 14.44, Enforcement/Penalties. (Ord. O20150006 § 2 (Att. A))