Chapter 16.20 STORMWATER

B. Provide sound development policies and construction procedures that respect and preserve the City’s watercourses in conformance with the latest edition of the Washington State Department of Ecology’s Stormwater Management Manual for the Puget Sound Basin.

C. Protect land and water bodies near development from increased surface water runoff rates and durations that could cause flooding, erosion and deposition of sediment as a result of construction activities.

D. Ensure the safety of City roads and rights-of-way and decrease drainage-related damage to public and private property.

E. Minimize water quality degradation of creeks, streams, ponds, lakes and other water bodies while preserving and enhancing the suitability of waters for recreation and fishing. (Ord. 2549 § 1, 2010).

16.20.020 Definitions.

“Adjustments” are changes to the minimum requirements which provide substantially equivalent environmental protection, are based on sound engineering practices, and meet the objectives of safety, function, and facility maintenance.

“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. The plan will include but not be limited to recommendations for: stormwater requirements for new development and redevelopment; capital improvement projects; land use management through identification and protection of critical areas, comprehensive land use and transportation plans, zoning regulations, site development standards, and conservation areas; source control activities including public education and involvement, and business programs; other targeted stormwater programs and activities, such as maintenance, inspections and enforcement; monitoring; and an implementation schedule and funding strategy. A plan that is “adopted and implemented” has the following characteristics: it has been adopted by legislative or regulatory action of jurisdictions with responsibilities under the plan; ordinances, regulations, programs, and procedures recommended by the plan are in effect or on schedule to be in effect; and an implementation schedule and funding strategy are in progress.

“Best management practice (BMP)” means schedules of activities, prohibition of practices, and structural and/or managerial practices that, when used singly or in combination, prevent or reduce the release of pollutants and other adverse impacts to waters of Washington State.

“Comprehensive drainage plan” refers to a detailed analysis for each drainage basin which compares the capabilities and needs for runoff accommodation due to various combinations of development, land use, structural and nonstructural management alternatives.

“Computations” means calculations, including coefficients and other pertinent data, made to determine the drainage plan with rates of flow of water given in cubic feet per second and cubic meters per second (CMS).

“Construction stormwater pollution prevention plan (SWPPP)” is a document that describes the potential for pollution problems on a construction project (defined as any exterior renovation that disturbs the ground) and explains and illustrates the measures to be taken on the construction site to control those problems.

“Critical areas” means those areas identified in accordance with Chapter 16.15 MTMC as wetlands, geologically hazardous areas, frequently flooded areas, and fish and wildlife habitat.

“Critical facility” means a facility for which even a slight chance of flooding might be too great. Critical facilities include, but are not limited to, schools, nursing homes, hospitals, police, fire and emergency response installations, and installations which produce, use or store hazardous materials or hazardous waste.

“Critical or sensitive sites” means critical areas.

“Department” means the Public Works Department or its assigns.

“Design storm” means a rainfall (or other precipitation) event or pattern of events for use in analyzing and designing drainage facilities, specifying both the return period in years and the duration in hours.

“Detention facilities” means facilities designed to hold runoff while gradually releasing it at a predetermined maximum rate.

“Developer” means the individual(s) or corporation(s) applying for the permits or approvals described in MTMC 16.20.060(A).

“Development” means any manmade change to improved or unimproved real estate including, but not limited to, buildings or other structures, mining, dredging, filling, grading, paving, excavation or drilling operations or storage of equipment and materials located within the area of special flood hazard.

“Director” means the City of Mountlake Terrace Public Works Director or his/her designee.

“Drainage plan” means a “stormwater site plan” as defined in this section.

“Erosion and sedimentation control” means any temporary or permanent measures taken to reduce erosion, control siltation and sedimentation and ensure that sediment-laden water does not leave a site.

“Flood” or “flooding” means a general and temporary condition of partial or complete inundation of normally dry land areas from:

1. The overflow of inland or tidal waters; and/or

2. The unusual and rapid accumulation of runoff of surface waters from any source.

“Ground water” means water in a saturated zone or stratum beneath the surface of the land or below a surface water body.

“Hard surface” means an impervious surface, a permeable pavement, or a vegetated roof.

“Impervious surface” means a hard surface area which either prevents or retards the entry of water into the soil mantle as under natural conditions prior to development, and/or a hard surface area which causes water to run off the surface in greater quantities or at an increased rate of flow from the flow present under natural conditions prior to development. Common impervious surfaces may include, but are not limited to, rooftops, walkways, patios, driveways, parking lots or storage areas, concrete or asphalt paving, gravel roads, packed earthen materials, and oiled, macadam or other surfaces which similarly impede the natural infiltration of storm and surface water.

“Land-disturbing activity” is any activity that results in a change in the existing soil cover (both vegetative and nonvegetative) 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, including landscape maintenance and gardening, are not considered land-disturbing activity. Stormwater facility maintenance is not considered land-disturbing activity if conducted according to established standards and procedures.

“Low impact development” means a stormwater and land use management strategy that strives to mimic pre-disturbance hydrologic processes of infiltration, filtration, storage, evaporation and transpiration by emphasizing conservation, use of on-site natural features, site planning, and distributed stormwater management practices that are integrated into a project design.

“Minimum requirements” for new development and redevelopment are:

1. Minimum Requirement No. 1: Preparation of Stormwater Site Plans;

2. Minimum Requirement No. 2: Construction Stormwater Pollution Prevention Plan;

3. Minimum Requirement No. 3: Source Control of Pollution;

4. Minimum Requirement No. 4: Preservation of Natural Drainage Systems and Outfalls;

5. Minimum Requirement No. 5: On-Site Stormwater Management;

6. Minimum Requirement No. 6: Runoff Treatment;

7. Minimum Requirement No. 7: Flow Control;

8. Minimum Requirement No. 8: Wetlands Protection; and

9. Minimum Requirement No. 9: Operation and Maintenance.

“Natural location of drainage systems” refers to the location of those channels, swales, and other nonmanmade conveyance systems as defined by the first documented topographic contours existing for the subject property, either from maps or photographs, or such other means as appropriate.

“New development” means land-disturbing activities; structural development, including construction, installation or expansion of a building or other structure; creation of impervious surfaces; and subdivision or short subdivision, and binding site plans as defined in Chapter 58.17 RCW.

“Peak discharge” means the maximum surface water runoff rate (cubic feet per second and cubic meters per second) determined for the design storm.

“Permanent stormwater control (PSC) plan” is a plan which includes permanent BMPs for the control of pollution from stormwater runoff after construction and/or land-disturbing activity has been completed.

“Pollutant” means any substance which, when added to water, would contaminate or alter the chemical, physical, or biological properties of any waters of the City’s drainage system or of the state. This includes a change in temperature, taste, color, turbidity, or odor of the waters, or such discharge of any liquid, gaseous, solid, radioactive, or other substance into any waters of the City’s drainage system or of the state as will or is likely to create a nuisance. It also includes any substance which renders such waters harmful, detrimental, or injurious to the public health, safety or welfare, or to domestic, commercial, industrial, agricultural, recreational, or other legitimate beneficial uses, or to livestock, wild animals, birds, fish, or other aquatic life.

“Project” means any proposed action to alter or develop a site or area which may also require drainage review.

“Receiving bodies of water” means creeks, streams, lakes, and other bodies of water into which waters are directed, either naturally, in manmade ditches, or in closed conduit systems.

“Redevelopment” means, 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.

“Retention facilities” means facilities designed to hold water for a considerable length of time and then consume it by evaporation, plant transpiration, or infiltration into the soil.

“Runoff” means water originating from rainfall and other precipitation that is found in drainage facilities, rivers, streams, springs, seeps, ponds, lakes and wetlands as well as shallow ground water.

“Stormwater” means that portion of precipitation that does not naturally percolate into the ground or evaporate, but flows via overland flow, interflow, channels or pipes into a defined surface water channel, or a constructed infiltration facility.

“Stormwater comprehensive plan” means the most current Mountlake Terrace Stormwater Comprehensive Plan, and including any subsequent amendments.

“Stormwater Manual” means the 2019 Stormwater Management Manual for Western Washington as prepared by, and as on file with, the Washington State Department of Ecology. The Stormwater Manual contains BMPs to prevent, control or treat pollution in stormwater and reduce other stormwater-related impacts to waters of the state. The Stormwater Manual is intended to provide guidance on measures necessary in western Washington to control the quantity and quality of stormwater runoff from new development and redevelopment.

“Stormwater site plan” is the comprehensive report containing all of the technical information and analysis necessary for regulatory agencies to evaluate a proposed new development or redevelopment project for compliance with stormwater requirements. Contents of the stormwater site plan will vary with the type and size of the project, and individual site characteristics. It includes a construction stormwater pollution prevention plan (construction SWPPP) and a permanent stormwater control plan (PSC plan).

“Subject property” means the tract of land which is the subject of the permit and/or approval action, and is defined by the full legal description of all parcels involved in the proposed development.

“Technical guidance manual” means the latest version of the Low Impact Development Technical Guidance Manual for Puget Sound (Puget Sound Action Team and Washington State University, Pierce County Extension).

“Variances” are exemptions from the obligation to follow minimum requirements on a project.

“Wetland” or “wetlands” means areas that are inundated or saturated by surface water or ground water at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs, and similar areas. Wetlands do not include those artificial wetlands intentionally created from nonwetland sites, including, but not limited to, irrigation and drainage ditches, grass-lined swales, canals, detention facilities, wastewater treatment facilities, farm ponds, and landscape amenities, or those wetlands created after July 1, 1990, that were unintentionally created as a result of the construction of a road, street or highway. Wetlands may include those artificial wetlands intentionally created from nonwetland areas to mitigate conversion of wetlands. (Ord. 2798 § 2, 2021; Ord. 2729 § 4, 2018; Ord. 2700 § 2, 2016; Ord. 2611 § 1, 2013; Ord. 2549 § 1, 2010).

16.20.030 Description of the surface water and storm drainage system.

The City has a storm and surface water drainage system, which includes watercourses, sloughs, streams, ponds, lakes, swamps, streets, ditches, conduits, culverts, and catch basins among others. The City controls this system either through fee ownership, formal easements, regulations, or by its prescriptive rights to pass storm and surface waters over private and public lands. (Ord. 2549 § 1, 2010).

16.20.040 Statement of authority.

The Director is charged with the administration of and compliance with this chapter. The Director is empowered to establish such administrative and physical procedures and guidelines as are required in the execution of the authority provided under this chapter. The Director’s authority shall include but not be limited to administration of the following:

A. Review of all development permits to determine that the permit requirements of this chapter have been satisfied; and

B. Review of all development permits to determine that all necessary permits have been obtained from those federal, state or local governmental agencies from which prior approval is required. (Ord. 2549 § 1, 2010).

16.20.050 Interpretation.

In the interpretation and application of this chapter, all provisions shall be:

A. Considered as minimum requirements;

B. Liberally construed in favor of the governing body; and

C. Deemed neither to limit nor repeal any other powers granted under state statutes. (Ord. 2549 § 1, 2010).

16.20.060 Applicability.

Compliance with the terms of this chapter shall be a requirement for the issuance of a civil site plan permit and any form of development permit or building permit affected thereby. In addition to other requirements for compliance with this chapter, the following conditions shall also apply:

A. Area of Applicability. These rules and regulations shall apply to all property within the incorporated boundaries of the City of Mountlake Terrace, and may also apply to the full extent provided by law to those lands which are outside the City boundaries which discharge storm and surface waters into, from, and through the City. Jurisdiction in those areas not within the City boundaries shall be subject to the provisions of intergovernmental agreements as they now exist or shall be later entered into or modified between the City and other affected neighboring jurisdictions.

All persons applying for any of the permits and/or approvals regarding the activities herein listed shall meet the minimum requirements for stormwater site design listed in MTMC 16.20.110, including those requirements of the Stormwater Manual. Construction work shall not begin until final approval (by signature) of the civil site plan is obtained including plans for construction and installation of structures and BMPs to meet the requirements of the Stormwater Manual.

1. Commercial, industrial, or multifamily site plan approval.

2. Subdivision development approval.

3. Short subdivision development approval.

4. Any alterations that affect a subject property’s runoff or soil percolation rates, if such property is within a critical or sensitive area.

5. New Development Proposal. All new development shall be required to comply with the Stormwater Manual Minimum Requirement No. 2.

a. The following new development shall comply with Stormwater Manual Minimum Requirements No. 1 through No. 5 for the new and replaced impervious surfaces and the land disturbed:

i. Creates or adds 2,000 square feet or greater of new, replaced, or new plus replaced impervious surface area; or

ii. Has land-disturbing activity of 7,000 square feet or greater.

b. The following new development shall comply with Stormwater Manual Minimum Requirements No. 1 through No. 9 for the new impervious surfaces and the converted pervious surfaces:

i. Creates or adds 5,000 square feet, or more, of new impervious surface area; or

ii. Converts three-quarters of one acre, or more, of native vegetation to lawn or landscaped areas; or

iii. Converts two and one-half acres, or more, of native vegetation to pasture.

6. Redevelopment. All redevelopment shall be required to comply with Stormwater Manual Minimum Requirement No. 2 (Construction Stormwater Pollution Prevention Plan). For non-road related commercial and industrial redevelopment, the value of the proposed improvements must be compared to the value of the project site (limits of disturbance) improvements, rather than the value of improvements of the entire parcel. In addition, all redevelopment shall be required to comply with additional minimum requirements of the Stormwater Manual as follows:

a. The following redevelopment shall comply with the Stormwater Manual Minimum Requirements No. 1 through No. 5 for the new and replaced impervious surfaces and the land disturbed:

i. The new, replaced, or total of new plus replaced impervious surfaces is 2,000 square feet or more; or

ii. Seven thousand square feet or more of land-disturbing activities.

b. The following redevelopment shall comply with Stormwater Manual Minimum Requirements No. 1 through No. 9 for the new impervious surfaces and converted pervious areas:

i. Adds 5,000 square feet or more of new impervious surfaces; or

ii. Converts three-quarters of one acre, or more, of native vegetation to lawn or landscaped areas; or

iii. Converts two and one-half acres, or more, of native vegetation to pasture.

c. If the runoff from the new impervious surfaces and converted pervious surfaces is not separated from runoff from other surfaces on the project site, the stormwater treatment facilities must be sized for the entire flow that is directed to them.

d. A project may provide stormwater management BMPs for an equivalent area. The equivalent area may be on site, or off site if the area drains to the same receiving water and the guidance for in-basin transfers as defined by the Stormwater Manual is followed.

Commencement of construction work under any of the above permits or applications shall not begin until such time as final approval of the drainage plan in conformance with the Stormwater Manual is obtained. Failure to comply with this provision shall result in revocation of all permits for the proposed development, and the City may proceed as authorized under MTMC 16.20.210 through 16.20.250.

B. Alteration of the Existing Drainage System. A considerable portion of the drainage system of the City presently exists as natural watercourses and wetlands. No person shall undertake a project which would encroach upon, modify, realign, or change in any manner any of the existing drainage system, except for normal maintenance, consistent with requirements of Chapter 16.15 MTMC.

C. Exceptions. See TLMC 16.20.150, Adjustments and variances. (Ord. 2798 § 3, 2021; Ord. 2549 § 1, 2010).

16.20.065 Basin plans.

Basin plans shall provide a mechanism by which the minimum requirements and BMP implementation for a project may be refined based on the analysis of a basin or watershed. Basin plans may also be used to develop control strategies to address impacts from future development and to correct specific problems whose sources are known or suspected. (Ord. 2798 § 4, 2021).

16.20.070 Applicability to governmental entities.

To the extent not prohibited, or as permitted or provided by law, all municipal corporations and governmental entities shall be required to submit a drainage plan and comply with the terms of this chapter when undertaking such projects or applying for such permits as stated in MTMC 16.20.060. This shall include road building and widening within the City.

It is recognized that many other City, county, state, and federal permit conditions may be applied to the proposed action and that compliance with the provisions of this chapter does not constitute compliance with other such requirements. (Ord. 2549 § 1, 2010).

16.20.080 Minimum standards for development projects.

A. All persons applying for any of the permits, approvals or undertaking items contained in MTMC 16.20.060(A) shall provide a temporary erosion/sedimentation control plan and a drainage plan stormwater site plan (drainage report) in conformance with the Stormwater Manual for surface water flows entering, flowing within, and leaving the subject property. The plans must include all information and details required by the Department.

B. Additional Plan Requirements. In addition to typical plan details, the Director may require information including but not limited to:

1. Soils, topography, existing vegetation, the areas to be cleared and graded, and the location of major cuts and fills covered by the permit and/or approval for which application is made.

2. Computations and hazards associated with the area covered by the permit and/or approval for which application is made.

3. Anticipated schedule of construction.

4. Soil logs.

5. Infiltration data.

6. Additional temporary erosion/sedimentation control measures to account for seasonal changes, alterations of the topography and watercourse during construction, and other such factors affecting site conditions which need to be considered to ensure complete siltation control on the subject property.

It shall be the obligation and responsibility of the person required to provide and maintain temporary erosion/sedimentation facilities pursuant to this section to address any new conditions that may be created by his activities and to utilize additional control measures as may be needed.

C. Failure to submit the materials required by this chapter shall be cause for the City to refuse to process the civil site plan application.

D. Clearing and Grading Permit. A clearing and grading permit is required for all projects with greater than 7,000 square feet of land-disturbing activities as defined in the Stormwater Manual and MTMC 16.20.020. Projects that result in less than this amount are not required to obtain a clearing and grading permit, but must consider all of the 13 elements of a construction stormwater pollution prevention plan as defined in the Stormwater Manual and MTMC 16.20.020, and develop controls for all elements that pertain to the project site. (Ord. 2798 § 5, 2021; Ord. 2729 § 5, 2018; Ord. 2549 § 1, 2010).

16.20.090 Low impact development (LID) drainage standards.

A. Low impact development BMPs are preferred over conventional stormwater management systems that rely on detention structures and closed conveyance systems. Use of LID BMPs may reduce or eliminate the need for conventional detention facilities but does not remove the obligation to comply with the minimum requirements of the Stormwater Manual. A variety of BMPs to minimize impervious surfaces and to manage stormwater have been developed and tested for use in western Washington.

B. LID BMPs identified in the Stormwater Manual and/or the most current version of City of Mountlake Terrace Engineering Details and Specifications as applicable are accepted for use in stormwater site plans to address the minimum requirements for flow control and runoff treatment.

C. The City of Mountlake Terrace requires the use of low impact development techniques as described in the Stormwater Manual. Where low impact development BMPs are proposed for installation, the BMP selection criteria, BMP design criteria, the BMP infeasibility criteria, LID competing needs criteria, and BMP limitations in the Stormwater Manual shall apply.

D. Restrictions on conversion of drainage facilities associated with subdivision plats shall be recorded on the face of the plat. A covenant shall be recorded with the Snohomish County Auditor’s Office for each lot containing or served by bioretention facilities in a form approved by the City Attorney. The covenant shall identify requirements and liability for preservation and maintenance of low impact development facilities approved under this chapter and privately held in individual or undivided ownership or intended for public ownership. (Ord. 2792 § 7, 2021; Ord. 2729 § 6, 2018; Ord. 2700 § 3, 2016; Ord. 2549 § 1, 2010).

16.20.095 Special considerations – Town Center.

Low impact development (LID) shall be implemented in the BC/D District insofar as LID principles and best management practices (BMPs) appropriate in an ultra-urban or high density setting can be applied, as described below.

A. Provisional Application. LID shall be applied to Town Center development consistent with Town Center standards insofar as BMPs do not preclude site coverage allowed in the district, or preclude pedestrian activity areas otherwise required in the district.

B. Street Improvements. Street improvements plans developed under the Main Street revitalization project for identified streets in the Town Center, as now and hereinafter amended and as on file with the City of Mountlake Terrace, are hereby incorporated by reference. (Ord. 2798 § 6, 2021; Ord. 2706 § 3, 2017).

16.20.100 Standards.

A. The Stormwater Manual, as defined in this chapter, is adopted and by this reference made a part of this chapter as though fully set forth herein.

B. Appendix 1 and Appendix 10 of the National Pollution Discharge Elimination System (NPDES) permit issued by the Department of Ecology to cover the City of Mountlake Terrace are adopted as though fully set forth herein including the thresholds, definitions, minimum requirements and exceptions, adjustment and variance criteria that it contains.

C. The standards set out in MTMC 16.20.110 shall apply to all projects subject to this chapter. Additionally, the water quality standards shall apply to all properties discharging storm and surface water runoff into the drainage system. Except where specifically described, it shall be the developer’s responsibility to determine the method of compliance with the standards. (Ord. 2798 § 7, 2021; Ord. 2700 § 4, 2016; Ord. 2549 § 1, 2010).

16.20.110 General design, construction and maintenance standards.

A. Mandatory Requirements.

1. Surface water entering the subject property shall be received at the naturally occurring location and surface water exiting the subject property shall be discharged at the naturally occurring location to the maximum extent practicable as determined by the Director with adequate energy dissipaters within the subject property to minimize downstream damage (and with no diversion at any of these points).

2. Where open channel construction is used to handle drainage within the subject property, and where LID BMPs cannot otherwise be used to handle drainage, the following standards shall apply:

a. A minimum of 15 feet will be provided between any structures and the top of the bank of the defined channel.

b. In open channel work the water surface elevation will be indicated on the plan and profile drawings. The configuration of the finished grades constituting the banks of the open channel will also be shown on the drawings.

c. Proposed cross-section of the channel will be shown with stable side slopes as approved by the Department.

d. The water surface elevation of the flow for the design storm will be indicated on the cross-section.

3. When an LID facility is used to manage stormwater within the subject property, system setbacks from buildings may be reduced, subject to City engineering review and the use of appropriate measures to protect building foundations. Evaluation of the recommendations of the site geotechnical report by City engineering will be the basis for determining whether or not system setbacks may be reduced.

4. All drainage easements granted to the City within the subject property shall be at least 20 feet in width for operation and maintenance of open-channel or closed-system installation.

5. Open retention/detention ponds and infiltration facilities serving private or commercial property shall not be located in dedicated public right-of-way areas unless they are part of a comprehensive LID approach to stormwater design for the abutting site and associated right-of-way, and unless specifically allowed by the Director.

6. An emergency overflow system is required for all retention/detention and infiltration facilities.

7. Stormwater retention/detention shall not occur on asphalt, graveled or concrete surfaces except those permeable surfaces that are part of an LID stormwater design as approved by the Director.

8. Where drainage facilities discharge to natural drainage ways or watercourses or both, energy dissipation facilities as approved by the Director shall be provided to minimize erosion and deterioration of the streambed or banks.

B. Infiltration. Infiltration of stormwater into the ground is required to the maximum extent practicable. To facilitate greater infiltration, locating platted development sites over less permeable soils (e.g., clay) is preferred to locating them over permeable soils. Infiltration potential for all projects shall be reviewed according to the requirements of the Stormwater Manual. Approved infiltration projects shall have an inflow capacity sufficient to handle the design storm. An overflow system shall be available for backup.

The approval of any infiltration project shall not constitute approval of any means by which unstable subsurface conditions may occur; such conditions resulting from infiltration projects not constructed by the City shall remain the responsibility of the developer.

C. Construction and Maintenance. Construction materials and methods shall be in accordance with the Standards and Specifications for Municipal Public Works Construction prepared by the American Public Works Association, latest edition, unless otherwise approved by the City. Copies of this publication are available for public inspection at the office of the Department. Maintenance methods shall be in accordance with the Stormwater Manual.

D. Discharge to Natural Drainage Ways. Where drainage facilities discharge to natural drainage ways or watercourses, energy dissipation facilities shall be provided to prevent erosion and deterioration of the streambed or banks. Energy dissipation facilities shall be constructed of approved materials. Material such as broken concrete slabs, pipe, tires, scrap metal or debris is prohibited. No person shall discharge drainage waters from their project to any point or in any manner not approved by the City. Prior to occupancy of the site or any related structure, permanent erosion control facilities must be established and operating at designed efficiency.

E. Detention Facilities. All detention facilities shall be designed in such a manner that the outlet structures are easily accessible for inspection, testing, and maintenance.

The release of runoff from the storage basin shall be through a weir, orifice, grate, pipeline, or any other structure or LID system approved by the Director and shall be maintained by the owner at his expense unless accepted for maintenance by the City as provided for under MTMC 16.20.200.

Where detention facilities are incorporated into the property development in the form of lakes or fountains, they shall be designed so as to avoid algae blooms and prevent stagnation. This area of concern shall be addressed in the permit application and may include requirements for maintenance.

All open detention facilities not incorporated into landscaping arrangements shall not retain water for more than 48 hours.

F. Wetlands. Where existing wetlands function as a control feature in the natural drainage system, no project will be permitted which reduces that control feature. Specific project requirements near wetlands shall be regulated under Chapter 16.15 MTMC, Critical Areas.

G. Development in areas where the 100-year floodplain has been established by a comprehensive drainage plan (Halls, Lyon and McAleer basins), or by flood insurance rate maps, or that are considered to be frequently flooded areas per Chapter 16.15 MTMC, or where the Community and Economic Development Department has determined that drainage or erosion conditions present an imminent potential of harm to the welfare and safety of the surrounding community shall meet special drainage conditions set by the Department. Conditions may include the limitation of the volume of discharge from the developed property to be predevelopment levels, preservation of wetlands or other natural drainage features, or other controls necessary to protect against a community hazard.

Due to the detrimental effect on upstream and downstream properties, no filling, grading or construction shall take place within the established floodplains where an equal amount of displaced flood water storage has not been provided elsewhere. The developer must provide information, plans and calculations to satisfy the Director that development within the floodplains is not detrimental by increasing the flooding occurring upstream or downstream from the site.

H. Use of Storm and Surface Water Runoff.

1. Drawdown. Storm and surface water runoff may be drawn in any quantity from manmade storage devices on private property which release directly into the drainage system or which are completely enclosed. No water may be drawn from the watercourses, sloughs, streams, ponds, lakes, or swamps that make up the public drainage system except under the provisions of approved state water rights permits.

2. Permitted Uses. Storm and surface water runoff that can legally be drawn off from the project area may be used for any nonpotable purposes. The distribution system employed shall be separate from the City water system.

I. Fish Passage. All projects involving perennial streams shall make adequate accommodation for fish passage. No obstructions of any kind shall be placed within the stream which would prohibit the free passage of fish under all flow conditions. (Ord. 2729 § 7, 2018; Ord. 2700 § 5, 2016; Ord. 2670 § 2, 2015; Ord. 2549 § 1, 2010).

16.20.120 Establishment of regional or subregional facilities.

A. In the event that public benefits would accrue due to modification of the stormwater site plan for the subject property to better implement the stormwater comprehensive plan, the Director may recommend that the City assume some responsibility for the further design, construction, operation and maintenance of a separate regional or subregional drainage facility either on the subject property or elsewhere in the drainage basin where drainage runoff from said property can be received. The decision to enter into the design, construction, operation and maintenance of a separate regional or subregional drainage facility shall be made by the City Council. In the event the City does assume responsibility for design, construction, and maintenance of the facilities, the applicant for a development that is within the area being serviced by the drainage facility shall be required to financially participate in the total construction cost as provided in subsection B of this section.

The City may require the dedication of land for construction within the subject property of regional or subregional facilities where such dedication is determined reasonable by the City Council with due regard for the requirement for on-site facilities, the development plan proposed, and the alternative uses of such lands proposed for dedication. Should construction of regional or subregional facilities require the acquisition of land on the subject property beyond a reasonable amount as determined by the City Council, or off the subject property, the City may consider the acquisition of such lands by the City’s applicable condemnation procedures with all such costs to be included within the construction costs of the facility.

The City Council may also elect to allow the developer to construct the regional or subregional facility. In such cases, the City will participate in the cost of the facility in an amount representing the additional cost to the applicant beyond his alternate costs.

B. Where the City has adopted a comprehensive drainage plan encompassing the basin of the subject property, or has constructed a regional or subregional facility adequate to service the subject property, the developer may utilize the regional or subregional stormwater facility in lieu of constructing all or some of the stormwater facilities otherwise required on the subject site [provided, however, participation in the regional or subregional facility shall not create an unsafe situation and any downstream manmade conveyance system shall have adequate capacity to convey flow from the proposed project or property to the regional or subregional facility site without flooding downstream properties]. To be able to utilize the regional or subregional drainage facility, the developer shall pay a pro rata share of the construction costs of said facility based on the amount of impervious surface area that the subject property will contribute to the facility. Such sum shall be as approved by the Director. Receipt of said sum shall relieve the developer of the requirement to construct on-site stormwater drainage facilities only to the extent that the regional or subregional facilities provide stormwater flow control and/or runoff treatment for the subject property, consistent with the City’s stormwater management standards in effect at the time the developer pays his/her pro rata share of the regional or subregional drainage facility costs. Such payment shall not guarantee that the drainage facility is adequate to accommodate future development or redevelopment of the site when newer stormwater management standards may be in effect.

C. The pro rata sum due for the subject property shall be paid prior to issuance of the civil permit. The developer is not required to purchase the entire capacity allowed for the subject property if such capacity is not needed to accommodate the development. Participation in a regional or subregional stormwater facility does not relieve the subject property of any Citywide stormwater utility fees that otherwise apply.

D. The City shall maintain a copy of each regional or subregional stormwater facility plan, a map of each regional facility basin, a complete list of all properties eligible to use the facility, and a list identifying the benefit share of the facility by percent and volume and the construction cost of the facility. (Ord. 2641 § 1, 2014; Ord. 2549 § 1, 2010).

16.20.130 Fees and charges.

All plan review, construction inspection and connection fees are as established in other City codes or resolutions. (Ord. 2549 § 1, 2010).

16.20.140 Review and approval of the plan.

Upon filing of the drainage plan, application and all supporting data as required by the City and upon payment of all applicable fees, the Director shall expeditiously review said permit request in accordance with the procedures established by the Department. If not categorically exempt, environmental review and determination and comment period required by the State Environmental Protection Act, as implemented by the City, shall be complete before plans shall be approved. The City will either approve the application, accept it on conditions as set forth in the approval, or deny it outright. Approval shall indicate initial approval of the plans and proposals as presented. Final approval and acceptance of the drainage facilities provided will only be made upon the completion of the project following necessary inspection, testing, and submittal of easements and maintenance guarantees. Unless required otherwise by the Department, the same plan submitted during one permit/approval process may be subsequently submitted with further required applications. The plan shall be supplemented with such additional information that is requested by the Director. (Ord. 2549 § 1, 2010).

16.20.150 Adjustments and variances.

A. Adjustments to the minimum requirements may be granted by the Director. Applicants must provide a narrative and any necessary supporting documentation describing the desired adjustment as written findings of fact, demonstrating that the adjustment:

1. Will neither seriously nor adversely impact the water quality conditions of any affected receiving bodies of water.

2. Will not alter the drainage patterns, increase the runoff volume or peak discharge, or cause any other adverse effects in the drainage area.

3. Will not cause runoff exceeding the available capacity of the existing drainage system where such system was designed to serve the proposed development area.

4. Will not reduce the flood-carrying capacity of any watercourse.

B. Variances may be permitted only after a determination by the Director of the validity of a variance. The Director may grant a variance if such application imposes a severe and unexpected economic hardship which prohibits reasonable use of the applicant’s property. To determine whether the application imposes a severe and unexpected economic hardship on the project applicant, the applicant must provide the Director with a narrative and any necessary supporting documentation, including written findings of fact, for the following information:

1. The current (pre-project) use of the site; and

2. How the application of the minimum requirement(s) per MTMC 16.20.020 restricts the proposed use of the site compared to restrictions that existed prior to the adoption of the minimum requirements; and

3. The possible remaining uses of the site if the exception were not granted; and

4. The uses of the site that would have been allowed prior to the adoption of the minimum requirements; and

5. A comparison of the estimated amount and percentage of value loss as a result of the minimum requirements versus the estimated amount and percentage of value loss as a result of requirements that existed prior to adoption of the minimum requirements; and

6. Whether or not there are special physical circumstances or conditions affecting the property such that the application of the minimum requirement would deprive the applicant of all reasonable use of the site in question; and

7. Whether or not every effort to find creative ways to meet the intent of this chapter’s provisions has been made; and

8. The feasibility for the owner to alter the project to apply the minimum requirements; and

9. How the exception is the least possible exception that could be granted to comply with the intent of the minimum requirements; and

10. How the exception will not increase risk to the public health and welfare, nor be injurious to other properties in the vicinity and/or downstream, or to the quality of waters of the state.

C. Requests for variance shall be filed in writing with the Director, including the payment of any fees established by the City, and shall adequately detail the basis of granting a variance. Variances require public notice (as described in Chapter 18.05 MTMC, Article III, Permit Review Procedures) for the variance application, public notice of the Director’s decision on the application, and written findings of fact that document the determination by the Director to grant the variance.

D. The decision of the Director concerning a request for a variance shall be made in writing.

E. When the Director determines that the applications of the provisions of this section will deny all reasonable use of the property, the restriction of development contained in this section may be waived only by the Hearing Examiner; provided, that the resulting development shall be subject to all of the remaining terms and conditions of this chapter. (Ord. 2798 § 8, 2021; Ord. 2549 § 1, 2010).

16.20.160 Appeals.

In the event of a permit denial, the City shall state the reasons for the denial and measures necessary to attain permit approval. The applicant shall have the right to appeal the denial with the Hearing Examiner, which shall have the effect of a final decision, or to make corrective measures to the project as necessary to obtain a permit. If the determination is not reversed, the applicant has the choice of correcting the project or permit application as required by the City or filing an appeal with Superior Court within 21 days of the Hearing Examiner’s decision. (Ord. 2549 § 1, 2010).

16.20.170 Easements.

Any easements required by the developer to pass drainage water from his property to an approved point of discharge to the City’s drainage system shall be obtained by the developer at his sole cost and expense. A true copy of such easement shall be delivered to the City prior to the time the developer commences work on this project. Upon completion of the project and prior to acceptance of said project by the City in accordance with the provisions hereof, the original easement and easement releases shall be delivered to the City. Said easement shall provide for the perpetual access of the City for maintenance, alteration, repair, and replacement of drainage-related facilities. (Ord. 2549 § 1, 2010).

16.20.180 Guarantee and liability insurance required.

The Department is authorized to require all persons constructing retention/detention or other drainage facilities to post guarantees of performance, operation, and maintenance. These guarantees are to ensure payment to the City for costs incurred when work must be performed and/or completed and/or corrective work must be undertaken to restore disturbed areas and eliminate hazards or erosion caused by work that is not completed, performed, or will result in damage. The only types of guarantees that are acceptable to the City of Mountlake Terrace are specified in Chapter 15.35 MTMC.

A. Construction Guarantee. Prior to commencing any vegetation removal from a construction site, the developer of the facility shall post a construction guarantee in an amount sufficient to cover the cost of conforming to said construction with the approved temporary siltation erosion control and approved drainage plans together with any administration cost incurred by the City should the City have to take corrective action in accordance with MTMC 16.20.220 through 16.20.270.

B. Maintenance Guarantee. After satisfactory completion of the construction guarantee by the City, the developer constructing the facility shall commence a two-year period of satisfactory maintenance of the facility. A maintenance guarantee must be posted to be used at the discretion of the Director to correct deficiencies in said maintenance affecting public health, safety, and welfare or violations of water quantity or quality standards of this chapter. Said guarantee must be posted and maintained throughout the two-year maintenance period. The amount of the guarantee shall be 20 percent of the estimated construction cost of the drainage facilities. In addition, the maintenance guarantee shall cover the cost of design defects or failures in workmanship of the facilities throughout the two-year maintenance period.

C. Liability Policy. The developer constructing the facility shall maintain a liability policy in the amount of $1,000,000, which shall name the City as an additional insured and which shall protect the City from any liability up to those amounts for any accident, negligence, failure of the facility, or any other liability whatsoever, relating to the construction or maintenance of the facility. Said liability policy shall be maintained for the duration of the facility by the owner of the facility; provided, that in the case of facilities assumed by the City for maintenance pursuant to MTMC 16.20.210, said liability policy shall be terminated when said City maintenance responsibility commences. (Ord. 2549 § 1, 2010).

16.20.190 Construction inspection and acceptance.

After issuance of the initial civil site construction permit for drainage conveyance, stormwater storage, or water quality facilities, the City shall be notified at the time any construction or alteration affecting drainage on the site shall begin and shall have the right to make periodic inspections during the construction or alteration to ensure that the requirements stated in the permit and elsewhere in this chapter are met. The property owner or developer must notify the City prior to the filling or cover of any subsurface drainage control facilities so that a proper inspection can be made. At the completion of the facilities, an inspection and test will be conducted at which time the property owner must illustrate to the City’s satisfaction that the drainage control facilities, which have been provided, function in accordance with the plans, specifications, and hydraulic computations as submitted with the permit applications and that all erosion control measures are operating efficiently. If all inspections and tests indicate that the projects and facilities have been completed in accordance with the requirements of the permit and this chapter, a final approval shall be given. Without this approval, or in the event of deficiencies not being corrected, no occupancy permit for the use of the property or any structures associated therewith will be granted by the Director until such time as the deficiencies are corrected. The property owner or developer shall make correction to any deficiency within 30 days. In the event the owner does not make such corrections within 30 days, the City reserves the right to take such corrective measures as may be necessary to make the system perform as required by the permit. All costs for corrective measures and enforcement actions shall be borne by the property owner and must be paid in full prior to granting an occupancy permit. (Ord. 2549 § 1, 2010).

16.20.200 City assumption of maintenance.

Developers proposing the transfer of operation and maintenance of required facilities to the City shall be required to design and construct facilities in a manner readily and efficiently serviceable by the City as determined by the Director. If the City is not to assume the maintenance of the retention/detention facilities, the developer shall make arrangements for assumption of maintenance in a manner approved by the Director. Any arrangement for the City to assume ownership or maintenance shall be completed and approved prior to the end of the two-year period of developer responsibility, and consistent with all City requirements. (Ord. 2549 § 1, 2010).

16.20.210 Civil penalty.

All civil penalties are as established in Chapter 19.140 MTMC, Enforcement. (Ord. 2798 § 9, 2021; Ord. 2729 § 8, 2018; Ord. 2700 § 6, 2016; Ord. 2549 § 1, 2010).

16.20.220 Notice of violation – Assessment of penalty.

Whenever the Director has found or determined that a violation is occurring, the Director is authorized to issue a notice of violation directed to the developer/owner.

A. The notice of violation shall contain:

1. The name and address of the applicant;

2. The street address when available or a legal description sufficient for identification of the building, structure, premises, or land upon or within which the violation is occurring;

3. A statement of the nature of such violation(s);

4. A statement of the action required to be taken as determined by the Director and a date for correction, which shall be not less than listed in this section, unless the Director has determined the violation to be hazardous and to require immediate corrective action or unless the corrective action constitutes an erosion control measure;

5. A statement that a cumulative civil penalty in the amount of $500.00 per day shall be assessed against the person to whom the notice of violation is directed for each and every day following the date set for correction on which the violation continues; and

6. A statement that the Director’s determination of violation may be appealed to the Hearing Examiner by filing written notice of appeal, in duplicate, with the Department within 10 calendar days of service of the notice of violation. The per diem civil penalty shall not accrue during the pendency of such administrative appeal unless the violation was determined by the Director to be hazardous and to require immediate corrective action or was determined by the Director to constitute a temporary erosion control measure.

B. The notice of violation shall be served upon the person(s) to whom it is directed either personally in the manner provided for personal service of notices or complaint in justice court or by mailing a copy of the notice of violation by certified mail, postage prepaid, return receipt requested, to such person at his last known address. Proof of personal service shall be made at the time of service by a written declaration under the penalty of perjury executed by the person affecting service, declaring time, date and the manner by which service was made.

C. A notice of violation issued pursuant to this section constitutes a determination from which an administrative appeal may be taken to the Hearing Examiner. In the event the cumulative civil penalty is not stayed during the appeal because the Director has determined either that the violation is hazardous and requires immediate corrective action or that the corrective action constitutes an erosion control measure, then the applicant shall be entitled to have the appeal considered by the City Manager within two working days following filing of the appeal.

D. For good cause shown, the Director may extend the date set for correction in the notice of violation; provided, that such an extension shall not affect or extend the time within which an administrative appeal must be commenced. (Ord. 2549 § 1, 2010).

16.20.230 Collection of civil penalty.

The civil penalty constitutes a personal obligation of the person(s) to whom the notice of violation is directed. The City Attorney, on behalf of the City, is authorized to collect the civil penalty by use of appropriate legal remedies, the seeking or granting of which shall neither stay nor terminate the accrual of additional per diem penalties so long as the violation continues. (Ord. 2549 § 1, 2010).

16.20.240 Compromise settlement and disposition of suits.

The Director and the City Attorney are hereby authorized to enter into negotiations with the parties or their legal representatives named in a lawsuit for the collection of civil penalties to negotiate a settlement, compromise or otherwise dispose of a lawsuit when to do so will be in the best interests of the City; provided, that a report shall be submitted to the City Council in any instance when a compromise settlement is negotiated. (Ord. 2549 § 1, 2010).

16.20.250 Corrective injunctions.

The City Council may institute a suit for a mandatory injunction directing a person to remove a structure or facility erected in violation of the provisions of this chapter, or make the same comply with its terms. If the City Council is successful in its suit, the respondent shall bear the costs of the action, including reasonable attorney fees. (Ord. 2549 § 1, 2010).

16.20.260 Failure of City to enforce.

The failure or refusal of the City to enforce any provision of this chapter, and as hereafter amended, shall not constitute a waiver or bar to prevent enforcement thereof against any person for a subsequent violation hereof, or for any other violation by any other person. (Ord. 2549 § 1, 2010).

16.20.270 Abrogation and greater restrictions.

This chapter is not intended to repeal, abrogate, or impair any existing easements, covenants, or deed restrictions. However, where this chapter and another ordinance, easement, covenant, or deed restriction conflict or overlap, whichever imposes the more stringent restrictions shall prevail. (Ord. 2549 § 1, 2010).