Chapter 12A.11STORMWATER MANAGEMENT

Sections:

12A.11.010
Purpose.
12A.11.020
General Provisions.
12A.11.030
Development Proposal Requirements.
12A.11.040
Minimum Surface Water and Stormwater Requirements.
12A.11.041
Repealed.
12A.11.042
Repealed.
12A.11.043
Repealed.
12A.11.044
Repealed.
12A.11.045
Repealed.
12A.11.046
Repealed.
12A.11.047
Repealed.
12A.11.048
Repealed.
12A.11.049
Repealed.
12A.11.050
Construction Timing and Final Approval.
12A.11.060
Illicit Discharge.
12A.11.010Purpose.

The purpose of this subchapter is to describe requirements for new development and redevelopment to:

A. Reduce flooding, erosion, and sedimentation;

B. Prevent and mitigate habitat loss;

C. Enhance groundwater recharge; and

D. Prevent surface and subsurface water pollution through the implementation of comprehensive and thorough permit review and construction inspection. (Ord. 501 § 3 (part), 2009.)

12A.11.020General Provisions.

All new development and redevelopment shall be served by an adequate stormwater management system as follows:

A. The proposed system is adequate if the development proposal site is served by a stormwater management system approved by the City Engineer as being consistent with the design, operating and procedural requirements adopted by the City. The project engineer shall submit a letter to the City certifying completeness of the stormwater management system in accordance with section 12A.060.020;

B. For a formal subdivision, special use permit or zone reclassification, the phased installation of required stormwater management improvements shall be stated in the approving documents. (Ord. 501 § 3 (part), 2009.)

12A.11.030Development Proposal Requirements.

A drainage review and approval is required when any development proposal is subject to a City permit. All proposals for development or redevelopment, whether public or private, which are submitted to the City for review and approval shall conform to these requirements which are to be used as the basis for review and approval of design and construction.

Development projects that capture and infiltrate all stormwater on site are also subject to these regulations, since these projects contribute to groundwater and have a probability of contributing stormwater to the City stormwater system in the event the design capacity is exceeded; or the system is compromised or fails.

Not all of the minimum requirements apply to every development or redevelopment project. The applicability varies depending on the type and size of the project. The flow charts in Figures 11.1 and 11.2 shall be used to determine which of the Minimum Requirements apply.

Figure 11.1: Flow Chart for Determining Requirements for New Development

Figure 11.2: Flow Chart for Determining Requirements for Redevelopment

(Ord. 648 § 4, 2016; Ord. 583 § 8, 2014; Ord. 501 § 3 (part), 2009.)

12A.11.040Minimum Surface Water and Stormwater Requirements.

When drainage review and approval is required the City requires, at a minimum, full compliance with this section.

A. Minimum Requirement #1: Preparation of Stormwater Site Plans. All projects meeting the thresholds in LMC 12A.11.030, Figure 11.1 or 11.2 shall prepare a stormwater site plan for City review. Stormwater site plans shall be prepared in accordance with the DOE Stormwater Manual as amended by the Engineering Standards Manual.

B. Minimum Requirement # 2: Construction Stormwater Pollution Prevention. All new development and redevelopment projects are responsible for preventing erosion and discharge of sediment and other pollutants leaving the site. Projects meeting the thresholds described in LMC 12A.11.030 Figure 11.1 or 11.2 shall prepare a construction stormwater pollution prevention plan (SWPPP) as part of the stormwater site plan (see Minimum Requirement #1). In addition, projects greater than one acre that have the potential to discharge to waters of the state, as determined by the City Engineer, shall apply for a construction stormwater general permit through the DOE. The permit, as well as guidance for preparing a SWPPP, is available through the DOE.

The SWPPP shall be implemented beginning with initial soil disturbance and until final stabilization. The SWPPP shall meet the following objectives:

1. To implement best management practices (BMPs) to prevent erosion and sedimentation, and to identify, reduce, eliminate or prevent stormwater contamination and water pollution from construction activity;

2. To prevent violations of surface water quality, ground water quality or sediment management standards; and

3. To control peak volumetric flow rates and velocities of stormwater discharges.

C. Minimum Requirement #3: Source Control of Pollution. All known, available and reasonable source control BMPs shall be applied to all projects. Source control BMPs shall be selected, designed, and maintained in accordance with the DOE Stormwater Manual and as amended by the Engineering Standards Manual.

D. Minimum Requirement #4: Preservation of Natural Drainage Systems and Outfalls. Natural drainage patterns shall be maintained, and discharges from the project site shall occur at the natural location, to the maximum extent practicable. The manner by which runoff is discharged from the project site shall not cause a significant adverse impact to downstream receiving waters and down gradient properties. All outfalls require energy dissipation.

E. Minimum Requirement #5: On-Site Stormwater Management. Projects shall employ on-site stormwater management BMPs in accordance with the project thresholds, standards, and lists found in Section 4.5 of Appendix 1 of the Western Washington Phase II Municipal Stormwater Permit (municipal NPDES permit) to infiltrate, disperse, and retain stormwater runoff on site to the maximum extent feasible without causing flooding or erosion impacts.

F. Minimum Requirement # 6: Runoff Treatment Project Thresholds. The following require construction of stormwater treatment facilities:

1. Projects in which the total of pollution-generating hard surface (PGHS) is 5,000 square feet or more in a threshold discharge area of the project, or

2. Projects in which the total of pollution-generating pervious surfaces (PGPS), not including permeable pavements, is three-quarters of an acre or more in a threshold discharge area, and from which there will be a surface discharge in a natural or manmade conveyance system from the site.

Treatment-type thresholds, facility sizing and facility selection, design and maintenance are as described in Section 4.6 of Appendix 1 of the municipal NPDES permit.

G. Minimum Requirement #7: Flow Control. Projects shall provide flow control to reduce the impacts of stormwater runoff from hard surfaces and land cover conversions. This requirement shall be interpreted as follows within the City of Lakewood:

• This minimum requirement applies to projects that discharge stormwater directly or indirectly through a conveyance or overflow system, into a fresh water body.

• This minimum requirement applies to projects that discharge stormwater to a City-owned conveyance system which subsequently infiltrates stormwater. However, for this scenario, the level of control required for such discharges will be approved on a site-by-site basis by the City Engineer. The intent is to ensure that drainage from the project site will not exceed the capacity of the downstream conveyance and/or the downstream infiltration system.

• This minimum requirement is waived for sites that will infiltrate on site all runoff from hard surfaces and converted vegetation areas.

Thresholds

The following require construction of flow control facilities and/or land use management BMPs that will achieve the standard requirements of the DOE Stormwater Manual:

1. Projects in which the total of effective impervious surfaces is 10,000 square feet or more in a threshold discharge area, or

2. Projects that convert three-quarters of an acre or more of native vegetation to lawn or landscape, or convert two and one-half acres or more of native vegetation to pasture in a threshold discharge area, and from which there is a surface discharge in a natural or manmade conveyance system from the site, or

3. Projects that through a combination of hard surfaces and converted vegetation areas cause a 0.10 cubic feet per second or greater increase in the 100-year flow frequency from a threshold discharge area as estimated using the Western Washington Hydrology Model or other approved model and one-hour time steps (or a 0.15 cfs increase or greater using 15-minute time steps).

Standard Flow Control Requirement

Stormwater discharges shall match developed discharge durations to pre-developed durations for the range of predeveloped discharge rates from 50 percent of the two-year peak flow up to the full 50-year peak flow. The pre-developed condition to be matched shall be a forested land cover unless:

1. Reasonable, historic information is provided that indicates the site was prairie prior to settlement (modeled as “pasture” in the Western Washington Hydrology Model); or

2. The drainage area of the immediate stream and all subsequent downstream basins have had at least 40 percent total impervious area since 1985. In this case, the predeveloped condition to be matched shall be the existing land cover condition. The map in Appendix I-G of the DOE Stormwater Manual depicts those areas which meet this criterion. Where basin-specific studies determine a stream channel to be unstable, even though the above criteria is met, the predeveloped condition assumption shall be the “historic” land cover condition or a land cover condition commensurate with achieving a target flow regime identified by an approved basin study.

This standard requirement is waived for sites that will reliably infiltrate on site all the runoff from hard surfaces and converted vegetation areas.

Alternative Requirement

An alternative requirement may be established through application of watershed-scale hydrological modeling and supporting field observations. Possible reasons for an alternative flow control requirement include the following:

1. Establishment of a stream-specific threshold of significant bed load movement other than the assumed 50 percent of the two-year peak flow;

2. Zoning and land clearing ordinance restrictions that, in combination with an alternative flow control standard, maintain or reduce the naturally occurring erosive forces on the stream channel; or

3. A duration control standard is not necessary for protection, maintenance, or restoration of designated beneficial uses or Clean Water Act compliance.

See Section 7 Basin/Watershed Planning of Appendix 1 of the municipal NPDES permit for details on how alternative control requirements may be established.

Additional Requirement

Flow control BMPs shall be selected, designed, and maintained in accordance with Volume III of the DOE Stormwater Manual or an approved equivalent.

H. Minimum Requirement #8: Wetlands Protection.

Applicability

The requirements below apply only to projects whose stormwater discharges into a wetland, either directly or indirectly through a conveyance system. These requirements shall be met in addition to meeting Minimum Requirement #6, Runoff Treatment; and Minimum Requirement # 7, Flow Control; and comply with the provisions of Chapter 14A.162 LMC, Wetlands Areas.

Standard Requirement

Projects shall comply with Guide Sheets #1 and #3 in Appendix I-D of the DOE Stormwater Manual. The hydrologic analysis shall use the existing land cover condition to determine the existing hydrologic conditions unless directed otherwise by a regulatory agency with jurisdiction.

Additional Requirements

The standard requirement does not excuse any discharge from the obligation to apply whatever technology is necessary to comply with state water quality standards, Chapter 173-201A WAC, or state groundwater standards, Chapter 173-200 WAC. Additional treatment requirements to meet those standards may be required by federal, state, or local governments.

Stormwater treatment and flow control facilities shall not be built within a natural vegetated buffer, except for necessary conveyance systems as approved by the City Engineer or as allowed in wetlands approved for hydrologic modification and/or treatment in accordance with the Guide Sheet #2 in Appendix I-D of the DOE Stormwater Manual.

An adopted and implemented basin plan prepared in accordance with provisions of Section 7 of Appendix 1 of the Municipal NPDES Permit, may be used to develop requirements for wetlands that are tailored to a specific basin.

I. Minimum Requirement #9: Operation and Maintenance. An operation and maintenance manual consistent with the provisions in Volume V of the DOE Stormwater Manual shall be provided for all proposed stormwater facilities and BMPs. The party (or parties) responsible for maintenance and operation shall be identified in the operation and maintenance manual. At private facilities, a copy of the manual shall be retained on site or within reasonable access to the site, and shall be transferred with the property to the new owner. For short plats and subdivisions, a plat agreement to follow the long term operation and maintenance plan shall be signed. For public facilities, a copy of the manual shall be retained in the appropriate department. A log of maintenance activity that indicates what actions were taken shall be kept and be available for inspection by the City. (Ord. 648 § 5, 2016; Ord. 501 § 3 (part), 2009.)

12A.11.041Minimum Requirement #2: Construction Stormwater Pollution Prevention. (Repealed)

(Repealed Ord. 648 § 9 (part), 2016; Ord. 501 § 3 (part), 2009.)

12A.11.042Minimum Requirement #3: Source Control of Pollution. (Repealed)

(Repealed Ord. 648 § 9 (part), 2016; Ord. 501 § 3 (part), 2009.)

12A.11.043Minimum Requirement #4: Preservation of Natural Drainage Systems and Outfalls. (Repealed)

(Repealed Ord. 648 § 9 (part), 2016; Ord. 501 § 3 (part), 2009.)

12A.11.044Minimum Requirement #5: On-Site Stormwater Management. (Repealed)

(Repealed Ord. 648 § 9 (part), 2016; Ord. 501 § 3 (part), 2009.)

12A.11.045Minimum Requirement #6: Runoff Treatment Project Thresholds. (Repealed)

(Repealed Ord. 648 § 9 (part), 2016; Ord. 501 § 3 (part), 2009.)

12A.11.046Minimum Requirement #7: Flow Control. (Repealed)

(Repealed Ord. 648 § 9 (part), 2016; Ord. 501 § 3 (part), 2009.)

12A.11.047Minimum Requirement #8: Wetlands Protection. (Repealed)

(Repealed Ord. 648 § 9 (part), 2016; Ord. 501 § 3 (part), 2009.)

12A.11.048Minimum Requirement #9: Basin/Watershed Planning. (Repealed)

(Repealed Ord. 648 § 9 (part), 2016; Ord. 501 § 3 (part), 2009.)

12A.11.049Minimum Requirement #10: Operation and Maintenance. (Repealed)

(Repealed Ord. 648 § 9 (part), 2016; Ord. 501 § 3 (part), 2009.)

12A.11.050Construction Timing and Final Approval.

Erosion and sediment control measures associated with both the interim and permanent drainage systems shall be:

A. Constructed in accordance with the approved plan prior to any grading or land clearing other than that associated with an approved erosion and sediment control plan; and

B. Satisfactorily sequenced and maintained until all improvements, restoration, and landscaping associated with the permit and/or for the project are completed, and the potential for onsite erosion has passed.

Prior to the construction of any improvements and/or buildings on the site, those portions of the drainage facilities necessary to accommodate the control of surface water and stormwater runoff discharging from the site shall be constructed and in operation. Recording of short plats and subdivisions may occur prior to the construction of drainage facilities when approved in writing by the City Engineer only to minimize impacts that may result from construction during inappropriate times of the year. If recording of formal or administrative subdivisions occurs prior to the construction of the drainage facilities then a financial guarantee will be posted to cover the cost of the unbuilt drainage facilities and a deadline for completion of the drainage facilities will be imposed. (Ord. 501 § 3 (part), 2009.)

12A.11.060Illicit Discharge.

A. Prohibited Discharges. It is unlawful for any individual, person, firm or corporation to discharge into the public storm drainage system directly or indirectly any liquid or solid foreign substances of biodegradable or other nature which may cause or tend to cause water pollution, including but not limited to the following items:

1. Petroleum and automotive products including but not limited to oil, gasoline, diesel fuel, grease, fuel oil and heating oil, antifreeze or other automotive products;

2. Trash, waste and debris including but not limited to food waste, garbage, pet wastes, sanitary sewage, bark and other fibrous material, lawn clippings, leaves or branches, animal carcasses, silt, sand, dirt or rock;

3. Chemicals, paints, paint chips, steam cleaning wastes, laundry wastes, soaps, pesticides, herbicides or fertilizers, degreasers and/or solvents, acids or alkalis, or dyes;

4. Heated water, chlorinated water or chlorine;

5. Construction materials including waste from washing of fresh concrete for cleaning and/or finishing purposes or to expose aggregates, mortar, gypsum, paint, or any other building materials.

B. Discharging of the following non-stormwater into the public storm drainage system directly or indirectly is illegal unless the stated conditions are met:

1. Discharges from potable water sources that have not been dechlorinated, including water line flushing, hyperchlorinated water line flushing, fire hydrant system flushing, and pipeline hydrostatic test water. Planned discharges shall be dechlorinated to a concentration of 0.1 ppm or less, pH-adjusted, if necessary, and volumetrically and velocity controlled to prevent resuspension of sediments in the City drainage system;

2. Dechlorinated swimming pool discharges. The discharges shall be dechlorinated to a concentration of 0.1 ppm or less, pH-adjusted and reoxygenized if necessary, volumetrically and velocity controlled to prevent resuspension of sediments in the City drainage system. Swimming pool cleaning wastewater and filter backwash shall not be discharged to the City drainage system;

3. Street and sidewalk wash water, water used to control dust, and routine external building wash down water at active construction sites. Street sweeping must be performed prior to washing the street;

4. Discharges shall be in compliance with the requirements of the stormwater pollution prevention plan reviewed by the City, which addresses control of construction site dewatering discharges.

C. Permissible Discharges. Discharges from the sources listed below shall only be considered illicit discharges if the City Engineer, or designee thereof, determines that the type of discharge, whether singly or in combination with others, is a significant source of water pollution:

Natural uncontaminated groundwater; uncontaminated air conditioning condensation; natural springs; uncontaminated water from crawl space pumps; irrigation runoff from agricultural sources that is commingled with urban stormwater; discharges in compliance with an NPDES permit; discharges from approved footing drains and foundation drains; diverted stream flows; flows from riparian habitat and wetlands; uncontaminated pumped groundwater; and rising groundwater.

D. Exemption. Discharges resulting directly from public firefighting activities, but not from such as the maintenance or cleaning of firefighting equipment, are exempt from regulation under this section.

E. Enforcement. The City Engineer, or the designee thereof or enforcement inspector or official, is authorized to enforce the regulations of this section through the following process or procedure:

1. Notice to Correct Violation. Whenever the code enforcement official or other authorized enforcement official, or his/her designee, determines that a violation of this section is occurring or has occurred, a written notice may be issued to correct the violation, with such notice being posted upon the property or delivered to the property owner(s) and/or tenant(s) and/or to any person(s) causing or allowing or participating in the violation.

2. Service of Notice. Such notice shall be served by posting the property, personally serving a copy of the notice upon a party responsible for the property, or by certified mail to the property owner or taxpayer of record for the property.

3. Notices pursuant to this section shall be in writing, shall state the specific violation to be remedied, the location of the violation, and the property owner and/or persons responsible for the property.

4. The code enforcement officer or inspecting official shall require the violation to be corrected within one to 15 working days from the issuance of the notice to correct. The length of time to correct shall be determined, in the sole discretion of the code enforcement official or other authorized enforcement official, or his/her designee, by the scope of violation, the history of prior violations by the same persons and/or at the same location and method needed to correct violation. All violations, in any event, shall be corrected expediently.

5. Failure to remedy a violation of this section after proper service of a notice to correct is a misdemeanor crime, punishable by up to 90 days in jail, a $1,000 fine or any combination thereof.

6. Public Nuisance. Violations of this section are public nuisances and may be abated by the City. LMC 12A.02.050, Public Nuisance. (Ord. 648 § 6, 2016; Ord. 583 § 9, 2014; Ord. 501 § 3 (part), 2009.)