Section 40.385.010

40.385.010 Introduction

A. Purpose. The purpose of this chapter is to safeguard public health, safety and welfare by protecting the quality of surface and groundwaters for drinking water supply, recreation, fishing and other beneficial uses through the application of best management practices (BMPs) for stormwater management and erosion control.

B. Applicability.

1. The provisions of this chapter shall apply to all new development, redevelopment, and drainage projects consistent with the Stormwater Management Manual for Western Washington (SMMWW) as modified by this chapter, and the county’s Stormwater Manual.

2. Applicability of this chapter may be modified by Sections 40.385.020(A)(8) and (9).

3. Meeting the requirements of this chapter is the joint and severable responsibility of both the owner(s) of the site on which land-disturbing activity occurs and the person(s) undertaking such activity. In addition, if the land-disturbing activity involves a county-issued permit, the applicant is also responsible for meeting the requirements of this chapter.

4. The responsible official is authorized to enforce the provisions of this chapter using the remedies and procedures in Title 32.

C. Exemptions.

1. Exemptions to the minimum requirements (listed in Section 40.385.010(D)) shall be granted for the following activities:

a. Forest practices regulated under Title 222 WAC, except Class IV general forest practices that are conversions from timber land to other uses.

b. Construction of agricultural buildings or other impervious surfaces for carrying out agricultural activities; provided, that no stormwater is released from the site directly or indirectly to the county’s stormwater conveyance system.

c. Normal landscape maintenance activities and gardening.

d. Oil and gas field activities or operations including construction of drilling sites, waste management pits, and access roads, as well as construction of transportation and treatment infrastructure such as pipelines, natural gas treatment plants, natural gas pipeline compressor stations, and crude oil pumping stations. Operators are encouraged to implement BMPs to minimize erosion and to control sediment during and after construction activities to help ensure protection of surface water quality during storm events.

e. The following road maintenance practices:

(1) Pothole and square cut patching;

(2) Overlaying existing asphalt or concrete pavement without expanding the area of coverage;

(3) Shoulder grading;

(4) Regrading/reshaping drainage systems;

(5) Crack sealing;

(6) Resurfacing with in-kind material without expanding the road prism; and

(7) Vegetation management.

2. Exemptions to specific minimum requirements shall be granted for the following activities:

a. The construction of single-family homes, duplexes, and their accessory structures may be exempt from minimum requirements No. 6 through No. 10; provided, that the project site is included in a stormwater plan previously approved by the county.

b. Drainage projects that are not new development or redevelopment and do not create new underground injection control wells are exempt from minimum requirement No. 6, and the responsible official may waive all or parts of minimum requirement No. 1 if the project meets other applicable requirements of this chapter.

c. 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.

d. New development and redevelopment meeting the criteria in Appendix I-E of the SMMWW are exempt from minimum requirement No. 7; provided, that:

(1) The discharge structure is designed to avoid erosion during all storms up to the one hundred (100) year storm; and

(2) If an existing discharge structure is used:

(a) The discharge structure must meet the requirements of Section 40.385.010(C)(2)(d)(1); and

(b) The discharge structure and conveyance system leading to the discharge must have adequate capacity to meet the requirements of this chapter.

e. In addition to the Columbia River, the Lewis River downstream of its confluence with Quartz Creek, and the East Fork of the Lewis River downstream of its confluence with Big Tree Creek, Appendix I-E of the SMMWW is appended to include Vancouver Lake and Lake River.

f. New development and redevelopment are exempt from wetland protection (minimum requirement No. 8); provided, that:

(1) The project does not change the rate, volume, duration, or location of discharges to and from the project site (e.g., where existing impervious surface is replaced with other impervious surface having similar runoff-generating characteristics, or where pipe/ditch modifications do not change existing discharge characteristics); or

(2) The project discharges to a slope wetland or riverine wetland where no depressional characteristics exist; or

(3) The project meets the land cover percentage requirements for full dispersion in accordance to SMMWW or the Stormwater Manual for flow control; or

(4) The county determines based on information in the preliminary stormwater plan, or information submitted for wetland review per Chapter 40.450, that the proposed project will not degrade wetland function.

3. New development and drainage projects undertaken by governmental agencies are exempt from Section 40.385.020(E)(5).

4. A proposed project is exempt from performing an off-site analysis if any of the following conditions apply:

a. The county determines based on the information in the final technical information report (TIR) that there is sufficient evidence to conclude that the project will not have a significant adverse impact on the downstream and/or upstream drainage system; or

b. The project:

(1) Adds less than two thousand (2,000) square feet of new impervious surface in the urban area or adds less than five percent (5%) of the site as new impervious surface in the rural area; and

(2) Adds less than thirty-five thousand (35,000) square feet of new pervious surface; and

(3) Does not construct or modify a drainage pipe/ditch that is twelve (12) inches or more in size/depth or that receives runoff from a drainage pipe/ditch that is twelve (12) inches or more in size/depth; and

(4) Does not contain or lie adjacent to a landslide, steep slope, or erosion hazard area; and

(5) The project is exempt from minimum requirement No. 8; or

c. The project does not change the rate, volume, duration, or location of discharges to and from the project site (e.g., where existing impervious surface is replaced with other impervious surface having similar runoff-generating characteristics, or where pipe/ditch modifications do not change existing discharge characteristics).

(Amended: Ord. 2009-12-01)

D. Definitions. For the purposes of this chapter, the following definitions shall apply. Additional definitions can be found in the SMMWW.


Basin plan	“Basin Plan” means a plan that assesses, evaluates, and proposes solutions to existing and potential future impacts to the beneficial uses of, and the physical, chemical, and biological properties of waters of the state within a basin.
Best management practices (BMPs)	“Best management practices (BMPs)” means schedules of activities, prohibitions of practices, maintenance procedures, managerial practices, or structural features that prevent or reduce adverse impacts to waters of Washington State.
Drainage project	“Drainage project” means the excavation or construction of pipes, culverts, channels, embankments or other flow-altering structures in any stream, stormwater facility or wetland in Clark County.
Impervious surface	“Impervious surface” means a hard surface that either prevents or retards the entry of water into the soil. Examples include, but are not limited to, structures, walkways, patios, driveways, carports, parking lots or storage areas, concrete or asphalt paving, gravel roads, packed earthen materials, haul roads and soil surface areas compacted by construction operations, and oiled or macadam surfaces. Open, uncovered retention/detention facilities shall not be considered as impervious surfaces for the purposes of determining whether the thresholds for application of minimum requirements are exceeded. Open, uncovered retention/detention facilities shall be considered impervious surfaces for purposes of runoff modeling.
Land-disturbing activity	“Land-disturbing activity” means any activity that results in movement of earth, or a change in the existing soil cover (both vegetative and non-vegetative) and/or the existing soil topography. Land-disturbing activities include, but are not limited to, clearing, grading, filling, and excavation. Compaction that is associated with stabilization of structures and road construction shall also be considered a land-disturbing activity. Vegetation maintenance practices are not considered land-disturbing activity.
Low impact development	“Low impact development” means a stormwater management strategy that emphasizes conservation and use of existing natural site features integrated with distributed, small-scale stormwater controls to more closely mimic natural hydrologic patterns in residential, commercial, and industrial settings.
Maintenance	“Maintenance” means repair and upkeep activities conducted on currently serviceable structures, facilities, and equipment that involves no expansion or use beyond that previously existing and results in no significant adverse hydrologic impact. It includes those usual activities taken to prevent a decline, lapse, or cessation in the use of structures and systems. Those usual activities may include replacement of dysfunctional facilities, including cases where environmental permits require replacing an existing structure with a different type structure, as long as the functioning characteristics of the original structure are not changed.
Minimum requirements	“Minimum requirements” means the ten (10) sets of requirements that are part of the SMMWW, as follows: • Minimum requirement No. 1: Preparation of stormwater site plans; • Minimum requirement No. 2: Construction stormwater pollution prevention; • Minimum requirement No. 3: Source control of pollution; • Minimum requirement No. 4: Preservation of natural drainage systems and outfalls; • Minimum requirement No. 5: On-site stormwater management; • Minimum requirement No. 6: Runoff treatment; • Minimum requirement No. 7: Flow control; • Minimum requirement No. 8: Wetlands protection; • Minimum requirement No. 9: Basin/watershed planning; and • Minimum requirement No. 10: Operation and maintenance.










Native vegetation	“Native vegetation” means plant species, other than noxious weeds, that are indigenous to the coastal region of the Pacific Northwest and which reasonably could have been expected to naturally occur on the site.
New development	“New development” means: • Land-disturbing activities, including Class IV general forest practices that are conversions from timber land to other uses; • Construction or installation of a building or other structure; • Creation of impervious surfaces; and • Subdivisions, short subdivisions, and binding site plans, as defined and applied in Chapter 58.17 RCW. Projects meeting the definition of redevelopment shall not be considered new development.





Pre-developed condition	“Pre-developed condition” means the land cover condition used to determine flow control requirements as required by Section 40.385.020(C)(2).
Project site	“Project site” means that portion of a property, properties, or right-of-way subject to land-disturbing activities, new impervious surfaces, or replaced impervious surfaces.
Redevelopment	“Redevelopment” means on a site that is already substantially developed (i.e., has thirty-five percent (35%) or more of existing impervious surface coverage): • The creation or addition of impervious surfaces; • The expansion of a building footprint or addition or replacement of a structure; • Construction, installation or expansion of a building or other structure; • Replacement of impervious surface that is not part of a routine maintenance activity; or • Land-disturbing activities.





Replaced impervious surface	“Replaced impervious surface” means: • For structures, the removal and replacement of any exterior impervious surfaces or foundation; or • For other impervious surfaces, the removal down to bare soil or base course plus the replacement.


Responsible official	“Responsible official” means the Director of Clark County Public Works or their designee.
Road-related development	“Road-related development” means land-disturbing activity where the sole objective is the development or redevelopment of roads, sidewalks and bike lanes.
Site	“Site” means the area within the legal boundaries of a parcel or parcels of land that is (are) subject to new development or redevelopment. For road projects, the length of the project site and the right-of-way boundaries define the site.
Stormwater Facility Maintenance Manual	“Stormwater Facility Maintenance Manual” means the January 2009 stormwater facility maintenance manual maintained by Clark County Public Works.
Stormwater Management Manual for Western Washington	“Stormwater Management Manual for Western Washington” (SMMWW) means the stormwater manual adopted by the Department of Ecology in February 2005.
Stormwater Manual	“Stormwater Manual” means the November 2009 stormwater manual maintained by Clark County Public Works.
Substantial completion	“Substantial completion” means: • Following inspection, stormwater facilities are operational and constructed to county standards; • Streets are constructed and at least one (1) lift of asphalt is installed when paving is required; and • The project is in full compliance with this chapter.



Underground injection control	“Underground injection control” means a manmade subsurface fluid distribution system designed to discharge fluids into the ground that consists of an assemblage of perforated pipes, drain tiles, or other similar mechanisms, or a dug hole whose depth is greater than the largest surface dimension.

(Amended: Ord. 2009-01-01; Ord. 2009-12-01)