Chapter 7.07
SURFACE WATER AND DRAINAGE CODE*

Sections:

7.07.010    Purpose.

7.07.020    Definitions.

7.07.030    Submission of a drainage plan.

7.07.040    Contents of a drainage plan.

7.07.050    Mandatory requirements for drainage improvements.

7.07.060    Development in critical areas.

7.07.070    Review and approval of the plan.

7.07.080    Establishment of regional facilities.

7.07.090    Bonds and liability insurance required.

7.07.100    City assumption of operation and maintenance.

7.07.110    Retroactivity relating to city maintenance of drainage facilities.

7.07.114    Construction standards.

7.07.117    Storm drainage system construction must comply with chapter.

7.07.120    Applicability to governmental entities.

7.07.130    Violations – Penalties.

7.07.140    Protection of public and private rights.

*Cross reference(s) – Department of public works, ch. 2.28; utility tax levied on telephone, gas, electric, garbage, water, sewer, and drainage utilities, ch. 3.18; street occupation permit, ch. 6.07; environmental policy, ch. 11.03; requirements and standards for subdivisions, ch. 12.04.

7.07.010 Purpose.

The city council finds that this surface water and drainage code is necessary in order to:

1. Promote sound development policies and construction procedures which respect and preserve the city’s watercourses;

2. Minimize water quality degradation and control the sedimentation of creeks, streams, ponds, lakes, and other water bodies;

3. Protect property owners adjacent to developing and developed land from increased run-off rates which could cause erosion of abutting property;

4. Protect downstream owners;

5. Preserve and enhance the suitability of waters for contact recreation and fishing;

6. Preserve and enhance the aesthetic quality of the waters;

7. Maintain and protect valuable groundwater resources;

8. Minimize adverse effects of alterations in groundwater quantities, locations, and flow patterns;

9. Ensure the safety of city and King County roads and rights-of-way; and

10. Decrease drainage related damage to public and private property.

(Ord. No. 2130, § 2. Formerly Code 1986, § 12.14.010)

7.07.020 Definitions.

The following words, terms and phrases, when used in this chapter, shall have the meanings ascribed to them in this section, except where the context clearly indicates a different meaning:

City engineer shall refer to the city of Kent city engineer.

Comprehensive drainage plan refers to a detailed analysis for each drainage basin which compares the capabilities and needs for run-off accommodation due to various combinations of development, land use, structural and nonstructural management alternatives. The plan recommends the form, location and extent of quantity and quality control measures which optimally would meet the legal constraints, water quality standards, and community standards, as well as identifying the institutional and funding requirements for plan implementation. Analysis of each drainage basin will depend upon specific criteria set forth by King County in order to identify critical drainage areas.

Computations shall mean 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 (cfs) and cubic meters per second (cms).

Design storm shall refer to that rainfall event which is selected by the public works department for purposes of design, specifying both the return period in years and the duration in hours.

Detention facilities shall mean facilities designed to hold run-off while gradually releasing it at a predetermined maximum rate.

Developer shall mean the individuals or corporations applying for the permits or approvals described in KCC 7.07.030 of this surface water and drainage code.

Developmental coverage shall mean all developed surface areas within the subject property including, but not limited to, rooftops, driveways, carports, accessory buildings, parking areas and any other impervious surfaces. During construction, developmental coverage shall include the above in addition to the full extent of any alteration of previously occurring soils, slope or vegetation due to grading, temporary storage, access areas or any other short-term causes.

Drainage area shall mean the watershed contributing water run-off to and including the subject property.

Drainage plan shall mean a plan for collection, transport, treatment and discharge or recycling of water within the subject property.

Drainage treatment/abatement facilities shall mean any facilities installed or constructed in conjunction with a drainage plan for the purpose of treatment or abatement of urban run-off, excluding retention or detention facilities.

Natural location of drainage systems shall refer to the location of those channels, swales, and other natural 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.

Peak discharge shall mean the maximum surface water run-off rate (cfs and cms) determined for the design storm.

Planned development shall refer to residential developments which are planned and/or developed in several stages but submitted together for approvals, and which typically consist of clusters of multi-unit structures interspersed with areas of common open space.

Procedures manual shall mean the manual of technical and administrative procedures established by the public works department which delineates methods to be used, the level of detail of analysis required, and other details for implementation of the provisions of this surface water and drainage code.

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

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

Planning department shall refer to the city planning department.

Public works department shall refer to the city public works department.

Subject property shall mean the tract of land which is the subject of a permit and/or approval action.

(Ord. No. 2130, § 2. Formerly Code 1986, § 12.14.010)

7.07.030 Submission of a drainage plan.

A. All developers applying for any of the following permits or approvals shall submit for approval a drainage plan with their application or request:

1. Grading permit;

2. Substantial development permit required under Chapter 90.58 RCW, shoreline management act;

3. Subdivision approval;

4. Short subdivision approval;

5. Rezones;

6. Conditional use permits;

7. Building permits where the permit relates to five thousand (5,000) or more square feet of development coverage within the property or where development is in a critical area as determined by the public works department;

8. Planned unit development.

B. Commencement of construction work under any of the permits in subsection (A) above or applications shall not begin until such time as final approval of the drainage plan is obtained in accordance with KCC 7.07.070.

C. The same plan submitted during one (1) permit/approval process may be subsequently submitted with further required applications. The plan shall be supplemented with such additional information as may be requested by the public works department or required by the provisions of the procedures manual.

D. The plan requirement established in this section will apply except when the developer demonstrates to the satisfaction of the public works and planning departments that the proposed activity or development:

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

2. Will not alter the surface discharge location, alter the drainage pattern or adjoining properties, alter drainage patterns, increase the discharge, nor cause any other adverse effects in the drainage area; and

3. Will not alter the subsurface drainage patterns, flowrates and discharge points, nor result in any significant adverse effects to property or residents.

(Ord. No. 2130, § 2. Formerly Code 1986, § 12.14.010)

7.07.040 Contents of a drainage plan.

All persons applying for any of the permits or approvals contained in KCC 7.07.030 shall provide a drainage plan for surface and pertinent subsurface water flows entering, flowing within and leaving the subject property both during and after construction. The detailed form and contents of the drainage plan shall be described in procedures established by the public works and planning departments, or in the procedures manual. The procedures manual will set forth the manner of presenting the following required information:

1. Background computations for sizing drainage facilities:

a. Depiction of the drainage area on a topographical map of approved scale and contour interval, with acreage of the site, development, and developmental coverage indicated;

b. Indication of the peak discharge and volume of run-off which will be generated due to the design storm within the subject property under its current use;

c. Indication of the peak discharge and volume of run-off which will be generated due to the design storm within the subject property if the development or proposed activity is allowed to proceed;

d. Determination of the peak discharge and volume of water that will be generated by the design storm at various points on the subject property.

2. Proposed measures for handling the computed run-off at the detail level specified in the procedures manual.

3. Proposed measures for controlling run-off during construction.

The requirements of this section may be modified at the discretion of the public works department in special cases requiring more information, with the concurrence of the planning department.

(Ord. No. 2130, § 2. Formerly Code 1986, § 12.14.010)

7.07.050 Mandatory requirements for drainage improvements.

A. Surface water entering the subject property shall be received at the naturally occurring locations and surface water exiting the subject property shall be discharged at the natural locations with adequate energy dissipaters within the subject property to minimize downstream damage and with no division at any of these points. The design storm peak discharge from the subject property may not be increased by the proposed development. Retention/detention facilities must be provided in order to maintain surface water discharge rates at or below the existing design storm peak discharge.

B. Where open channel construction is used to handle drainage within the subject property, a minimum of fifteen (15) feet will be provided between any structures and the top of the bank of the defined channel. 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. Proposed cross section of the channel will be shown with stable side slopes as approved by the public works department. The water surface elevation of the flow for the design storm will be indicated on the cross section.

C. When a closed system is used to handle drainage within the subject property, the system will be a minimum of ten (10) feet from all structures.

D. To the extent possible, approved measures for controlling run-off during construction should comply with the provisions in this section.

E. Variances from the requirements of subsections (A) through (C) above may be permitted only after a determination by the public works and planning departments, using the comprehensive drainage plan, if available, or employing the following criteria:

1. Sufficient capacity of downstream facilities under design conditions;

2. Maintenance of the integrity of the receiving waters;

3. Possibility of adverse effects of retention/detention;

4. Utility of regional retention/detention facilities;

5. Capability of maintenance of the system; and

6. Structural integrity of abutting foundations and structures.

Request for variances shall be filed in writing with the public works department and shall adequately detail the basis for requesting the variance.

(Ord. No. 2130, § 2. Formerly Code 1986, § 12.14.010)

7.07.060 Development in critical areas.

Development which would increase the volume or rate of discharge due to any storm from the subject property shall not be permitted in areas designated as critical areas by the city council. Critical areas are those in which existing flooding, drainage, erosion, or unstable conditions present an imminent likelihood of harm to the welfare and safety of the surrounding community, or to the integrity of the surface water or groundwater system. Development shall not be permitted in these critical areas until such time as the existing community hazard is alleviated and it is adequately demonstrated that the proposed development will not cause a recurrence of the problem nor the occurrence of any new drainage-related problem. The public works and planning departments may designate as critical any area in which comparable problems would occur in the future due to any increase in volume or peak discharge. The requirements of this section shall apply regardless of any exemption under KCC 7.07.030(D). Where applications of the provisions of this section will deny all reasonable uses of the property, the restrictions on development contained in this section may be waived for the subject property; provided, that the resulting development shall be subject to all the remaining terms and conditions of the surface water and drainage code. All decisions based on the provision of this section shall be compatible with the comprehensive drainage plan, if available, for the basin in which the subject property is located. For development in areas designated as critical, the developer shall provide information regarding volume and rate of discharge for a range of storms as specified in the procedures manual. The designation of critical drainage areas within the city limits will depend upon criteria set forth by King County.

(Ord. No. 2130, § 2. Formerly Code 1986, § 12.14.010)

7.07.070 Review and approval of the plan.

All storm drainage plans prepared in connection with any of the permits or approvals listed in KCC 7.07.030 shall be submitted for review by and approval of the public works and planning departments, in accordance with the procedures established in the procedures manual. At the time of approval of the drainage plan for the subject property, a schedule for inspection of construction and facilities will be established by the public works department.

(Ord. No. 2130, § 2. Formerly Code 1986, § 12.14.010)

7.07.080 Establishment of regional facilities.

In the event that public benefits would accrue due to modification of the drainage plan for the subject property to better implement the recommendations of the comprehensive drainage plan, the department of public works, or the planning department may recommend that the city should assume responsibility for the further design, construction, operation and maintenance of drainage facilities on the subject property. Such decision shall be made concurrently with review and approval of the plan as specified in KCC 7.07.070. If the city decides to assume responsibility for design, construction, operation and maintenance of the facilities, the developer will be required to contribute a pro-rata share to the construction cost of the facilities. The developer may be required to supply additional information at the request of the department of public works to aid in the determination by the city. Guidelines for implementing this section will be defined in the procedures manual or by the department of public works and planning department.

(Ord. No. 2130, § 2. Formerly Code 1986, § 12.14.010)

7.07.090 Bonds and liability insurance required.

A. The public works department is authorized to require all persons constructing retention/detention or other drainage treatment/abatement facilities to post surety and cash bonds. Where such persons have previously posted or are required to post other such bonds on the facility itself or on other construction related to the facility, such person may with the permission of the department of public works and to the extent allowable by law combine all such bonds into a single bond. At no time shall the amount thus bonded be less than the total amount which would have been required in the form of separate bonds. Such a bond shall on its face clearly delineate those separate bonds which it is intended to replace.

B. Prior to commencing construction, the person constructing the facility shall post a construction bond, or other security in an amount sufficient to cover the cost of conforming such construction with the approved drainage plans. The amount of the bond or security shall reflect the costs of the approved drainage plan and shall be increased at one (1) year intervals in a proportion equivalent to the prevailing rate of inflation in construction costs as specified in the procedures manual. After determination by the department of public works that all facilities are constructed in compliance with the approved plans and upon receipt of the maintenance bond required in subsection (C) below, the construction bond shall be released. At the city’s option, an assignment of savings, letter of credit or some other form of guarantee acceptable to the city may be substituted for the bond requirement.

C. After satisfactory completion of the facilities and release of the construction bond by the city, the person constructing the facility shall commence a one (1) year period of satisfactory maintenance of the facility. A cash bond or other security instrument excluding security bonds to be used at the discretion of the public works department to correct deficiencies in the maintenance affecting public health, safety and welfare must be posted and maintained throughout the one (1) year maintenance period. The amount of the maintenance bond shall be determined by the public works department, but shall not be in excess of fifteen (15) percent nor less than ten (10) percent of the construction cost of the drainage facilities. In addition, a surety bond or cash bond to cover the cost of design defects or failures in workmanship of the facilities shall also be posted and maintained throughout the one (1) year maintenance period. At the city’s option, an assignment of savings, letter of credit, or some other form of guarantee acceptable to the city may be substituted for the bond requirement.

D. The person constructing the facility shall provide liability insurance in accordance with the latest edition of Standard Specifications for Road, Bridge and Municipal Construction or in such other form, type, and amount as required by the public works department. At a minimum, the city shall be named as an additional insured and the insurance shall protect the city from any liability for any accident, negligence, failure of the facility, or any other liability whatsoever, relating to the construction or maintenance of the facility. The liability insurance shall be provided during construction and for the required period of maintenance following construction; provided, that in the case of facilities assumed by the city for maintenance pursuant to KCC 7.07.100, the requirement to provide insurance shall terminate when the city assumes maintenance responsibility.

(Ord. No. 2130, § 2; Ord. No. 3208, § 1, 1-17-95. Formerly Code 1986, § 12.14.010)

7.07.100 City assumption of operation and maintenance.

A. The city may assume the operation and maintenance responsibility of retention/detention or other drainage treatment abatement facilities after the expiration of the one (1) year operation and maintenance period in connection with the subdivision of land; if:

1. All of the requirements of KCC 7.07.090 have been fully complied with;

2. The facilities have been inspected and approved by the department of public works after one (1) year of operation in accordance with the procedures manual;

3. All necessary easements entitling the city to properly operate and maintain the facility have been conveyed to the city and recorded with the King County auditor;

4. The surety bond or other security in KCC 7.07.090 has been extended for one (1) year, covering the city’s first year of operation and maintenance; and

5. The developer has supplied to the city an accounting of capital, construction and operation and maintenance expenses or other items, for the drainage facilities up to the end of the one (1) year period, for the purpose of establishing the basis for future bonding requirements for other developments.

B. If the city elects not to assume operation and maintenance responsibility for the facilities it will be the responsibility of the developer to make arrangements with the occupants or owners of the subject property for assumption of operation and maintenance in a manner subject to the approval of the department of public works or in accordance with the procedures manual. Such arrangements shall be completed and approved prior to the end of the one (1) year period of developer responsibility.

C. If the city elects not to assume operation and maintenance responsibility, the drainage facilities shall be operated and maintained in accordance with the arrangements as approved by the department of public works. The city may inspect the facilities in order to ensure continued use of the facilities for the purposes for which they were built and in accordance with these arrangements.

(Ord. No. 2130, § 2; Ord. No. 3208, § 2, 1-17-95. Formerly Code 1986, § 12.14.010)

7.07.110 Retroactivity relating to city maintenance of drainage facilities.

A. If any person constructing retention/detention or other drainage treatment/abatement facilities and/or receiving approval of drainage plans prior to December 10, 1978, reevaluates according to the requirements of this chapter the facilities and/or plans so constructed and/or approved and demonstrates to the public works department’s satisfaction acceptable compliance with its requirements, the city may, after inspection, approval, and acknowledgment of the proper posting of the required bonds or other security as specified in KCC 7.07.090, assume operation and maintenance responsibility of the facilities.

B. In cases in which all or part of the drainage facilities are not accessible for operation or maintenance purposes due to overlying structures or other causes, the city shall be held harmless for damages which might occur due to failure of design or workmanship of those segments, and further will not be responsible for their maintenance, replacement or rehabilitation. In such cases, responsibility shall revert to the existing owner of such facilities.

(Ord. No. 2130, § 2. Formerly Code 1986, § 12.14.010)

7.07.114 Construction standards.

All surface water and storm drainage systems, whether public or private, shall be installed in strict accordance with specifications contained in any existing city ordinance or code and any construction standards or international or uniform codes that the city either has adopted or adopts in the future. All construction and maintenance of those systems shall be subject to the inspection by the director or his or her designee.

(Ord. No. 3400, § 3, 4-21-98; Ord. No. 3690, § 7, 5-4-04)

7.07.117 Storm drainage system construction must comply with chapter.

When any surface water or storm drainage facility, whether upon private property or upon the city’s right-of-way, is constructed, laid, connected, or repaired and does not comply with the provisions of this chapter or any construction standards or codes that may be adopted in the future, or where the director determines that a surface water or storm drainage facility is obstructed, broken, or inadequate and is a menace to health, or is liable to cause damage to public or private property, the director shall give notice of that condition to the owner, agent, or occupant of the property in which the condition exists. If the owner, agent, or occupant refuses to construct, relay, reconstruct, or remove the obstruction from the surface water or storm drainage facility within the time specified in that notice, the director may perform all necessary work to comply with this chapter. The cost of that work will be assessed against the property or collected from the person responsible for the condition, and the total amount thereof shall become a lien upon the property. The city attorney is authorized, empowered, and directed to collect that cost, either by foreclosure of the lien or by a suit against the owner, agent, occupant, or other person responsible for the condition on the property. The suit shall be maintained in the name of the city in any court of competent jurisdiction.

(Ord. No. 3400, § 4, 4-21-98)

7.07.120 Applicability to governmental entities.

All municipal corporations and governmental entities shall be required to submit a drainage plan and comply with the terms of this chapter when developing or improving land including, but not limited to, road building and widening, within the city. It is recognized that many other city, county, state, and federal permit conditions may apply to the proposed action and that compliance with the provisions of this chapter does not constitute compliance with such other requirements.

(Ord. No. 2130, § 2. Formerly Code 1986, § 12.14.010)

7.07.130 Violations – Penalties.

Violations of this chapter shall subject the violator to a fine in any sum not to exceed five hundred dollars ($500) or imprisonment for a period not to exceed thirty (30) days, or both such fine and imprisonment. As an alternative method of enforcement the city may initiate an action to enjoin any development undertaken in violation of this chapter by making application for an injunction in any court of competent jurisdiction, and may also commence a civil action in any court of competent jurisdiction to recover any penalty provided for in this section.

(Ord. No. 2130, § 2. Formerly Code 1986, § 12.14.010)

7.07.140 Protection of public and private rights.

Implementation of any provision of this chapter shall not cause nor be construed as an infringement of the rights of individuals, municipalities or corporations other than the developer seeking a permit or approval as described in KCC 7.07.030.

(Ord. No. 2130, § 2. Formerly Code 1986, § 12.14.010)