(A) Title. This section shall be known as the erosion prevention and sediment control and storm and surface water management ordinance. Divisions (C) to (G) relate to erosion prevention and sediment control. Divisions (H) to (N) relate to storm and surface water management.
(B) Definitions. For the purpose of this section, the following definitions shall apply unless the context clearly indicates or requires a different meaning.
BEST MANAGEMENT PRACTICES (BMPS).
(a) Erosion prevention and sediment control, and storm and surface water management regulations are listed in the Oregon Department of Environment Quality (DEQ) and National Marine Fishery Services (NMFS) manuals as follows:
1. Erosion and Sediment Control Manual which may be found at: http://www.deq.state.or.us/wq/stormwater/escmanual.htm;
2. Storm Water Discharges Associated with Construction Activities which may be found at: http://www.deq.state.or.us/wq/stormwater/docs/nwr/indbmps.pdf; and
3. Standard Local Operating Procedures for Endangered Species (SLOPES) which may be found at:
https://pcts.nmfs.noaa.gov/pls/pcts-pub/sxn7.pcts_upload.download?p_file=F15992/2008_08-13_SL OPES IV_Transportation_200804070.pdf.
(b) Hard copies of these documents may also be available at City Hall.
CLEAN WATER ACT (CWA). The Federal Water Pollution Control Act.
DIRECTOR. The City Manager or his or her designee.
EROSION. The process in which, by action of wind or water, soil particles are displaced and transported. Type of EROSION includes, but are not limited to, the following:
(a) GULLY. Concentrated flow, head cutting and down cutting;
(b) RILL. Increased topographic relief, higher run-off velocities and soil incision;
(c) SPLASH. Raindrop impact, dispersal and mobilization of soil particles;
(d) SHEET. Saturated soils, soil particles entrained in run-off water and uniform removal; and
(d) STREAM BANK. Natural drainage patterns, toe cutting and bank sloughing.
EROSION PREVENTION. Any practice that protects the soil surface and prevents soil particles from being detached by rainfall or wind.
IMPERVIOUS SURFACES. Mainly constructed surfaces, such as rooftops, sidewalks, roads and parking lots that are covered by impenetrable materials such as asphalt, concrete, brick and stone. These materials seal surfaces, repel water and prevent precipitation and meltwater from infiltrating soils. Soils compacted by urban development may also be highly impervious.
NATIONAL POLLUTANT DISCHARGE ELIMINATION SYSTEM (NPDES). In addition to local approval, DEQ issues 1200-C NPDES permits for sites that disturb over one acre.
PERVIOUS SURFACE. The opposite of impervious surface; allows water to percolate down into the ground and not sheet off to drainages. Examples of pervious surfaces: preserve/retain existing vegetation, pervious concrete which allows water to pass through and vegetated drainage ditches rather than culverts-bioswales.
SEDIMENT. Eroded material suspended in wind or water.
SEDIMENT CONTROL. Any practice that traps the soil particles after they have been detached and moved by wind or water. SEDIMENT CONTROL measures are usually passive systems that rely on filtering or settling the particles out of the water or wind that is transporting them.
SEDIMENTATION. The deposition of eroded material.
STATE DEPARTMENT OF ENVIRONMENTAL QUALITY (DEQ). The state agency that oversees water quality permits and implements federal CWA requirements.
STORMWATER RUNOFF. Occurs when precipitation from rain or snowmelt flows over the ground. Impervious surfaces like driveways, sidewalks and streets prevent stormwater runoff from naturally soaking into the ground.
(C) Purposes of erosion prevention and sediment control. The purposes of the erosion prevention and sediment control are:
(1) To preserve or enhance the health, safety, welfare and quality of life of the inhabitants of the city by providing clean water, and by minimizing risk to inhabitants and property through control of erosion; and
(2) To maintain or improve water quality within the city consistent with the requirements of the state and the United States government. This section seeks to accomplish these purposes by requiring measures to prevent erosion, control sediment and properly manage runoff from sites with disturbed soils. All development activity shall comply with the requirements for erosion prevention and sediment control. The intent of these provisions is to minimize the amount of sediment and pollutants that exit the site of development activity and, thereby, minimize the amount of such material that reaches waterways, wetlands, public improvements and the property of others. These provisions are intended to require that temporary and permanent measures be taken for all development activity that require or result in the disturbance of the surface of soil and/or vegetation.
(D) Applicability.
(1) The erosion prevention and sediment control provisions are applicable to all lands within the city at the date of an application for approval of development activity that can result in altered or increased runoff, erosion and sediment. Development activity includes, but is not limited to, vegetation removal, grading, construction of improvements, landscaping and other activities that disturb the surface of the soil. Measures must be taken to manage site hazards such as water runoff, soil erosion and sediment deposition. Except as otherwise provided in this division (D), this section applies to all development activities that:
(a) Will result in the excavation of 800 square feet or more of soil surface; or
(b) Will result in the construction of either 2,000 square feet of impervious surface on a site or will result in the coverage of 25% or more of the area of a site in impervious surfaces, whichever is less.
(2) Notwithstanding the provisions in division (D)(1) above, this section does not apply to the following:
(a) Home gardening that disturbs less than one-quarter of an acre;
(b) Activities undertaken to control invasive bush species for fire control purposes or for the preservation of pre-existing clearings or meadows; or
(c) Activities undertaken for the purpose of exploration such as backhoe pits and bore holes not requiring newly constructed road access.
(E) Erosion prevention and sediment control plan.
(1) Applications for authorization to undertake development and other activities described in division (D) above must be accompanied by an erosion prevention and sediment control plan.
(2) The erosion prevention and sediment control plan shall:
(a) Demonstrate that the subject property will not be disturbed, excavated, filled or developed so as to cause movement of mud, soil, rock, vegetative material or any products of erosion or other depositional material onto, deposited upon or transported to the property of another;
(b) Include specific interim and permanent measures that will prevent erosion and control sedimentation on the subject property and meet the requirements of division (E)(2)(a) above;
(c) Include a strategy to minimize the removal of vegetation cover, particularly tree cover, necessary for access, building placement or to establish views for proposed structures or improvements; and
(d) In cases of development activity that will result in the division of land, include both interim and permanent measures and improvements that must be taken and installed during the development of each lot or parcel created.
(3) Preparation of erosion prevention and sediment control plans shall be as follows.
(a) On a single lot or parcel on which the development activity will occur on slopes of less than 15%, the plan may be prepared by the applicant utilizing best management practices. Plans for development activities that will result in the division of land may not be prepared pursuant to this division (E)(3)(a).
(b) Development activities on properties that were created pursuant to an application and for which an erosion prevention and sediment control plan was approved shall comply with the provisions of that plan and may submit that plan in compliance with the requirements of this section.
(c) On lands on which the development or other activity will occur on slopes of 15% or greater, the plan must be prepared by a geologist.
(d) Plans prepared in geologic hazard areas must also be prepared in consultation with, and be signed by, a geologist.
(e) Final recorded plats and subdivision maps shall indicate that all lots or parcels must be developed consistent with the approved erosion prevention and sediment control plan and that the measures and improvements specified in the plan must be maintained by the owner of each lot or parcel.
(f) The applicant or owner of any lot or parcel on which an erosion prevention and sediment control plan has been approved shall record on the title to the subject property a notification of the existence of the plan, of the fact that it can be reviewed in the Planning Division files and that also specifies the obligation of subsequent land owners to refrain from interfering with such measures or improvements and to maintain them.
(F) Review and approval of an erosion prevention and sediment control plan.
(1) The Director shall review all applications for development activity for conformance with the standards and criteria of this section.
(2) The Director may retain decision-making authority over matters subject to administrative review or may refer such matters to the Planning Commission consistent with the provisions of §§ 153.205 through 153.210, 153.225 through 153.231, 153.245 through 153.254, 153.265 through 153.268, 153.280 through 153.283, 153.295 through 153.299 and 153.310 through 153.314.
(3) The Director or the Planning Commission may approve, approve with conditions, require changes to or deny the application based upon the criteria or standards listed in division (E) above.
(4) The Director shall review the proposed erosion prevention and sedimentation control plan for consistency with the requirements and purposes of these provisions and may approve, approve with conditions, require changes to or deny the application based and such review.
(5) No activities may be conducted on the property that is the subject of such a plan prior to the Director’s written approval thereof or prior to the installation of the approved erosion prevention and sedimentation control measures.
(6) If prior to applying for a permit or other authorization, vegetation removal is required to allow surveying and/or site study, the applicant shall submit a plot plan to the Director describing the amount and location of vegetation removal. If the property has slopes greater than 15%, vegetation can only be cut off at or above ground level. Stumps and roots shall not be removed. The Director must approve this plan prior to any removal of vegetation.
(G) Installation and certification of erosion prevention and sediment control measures.
(1) The approved erosion prevention and sediment control measures shall be installed and maintained as required by the approved plan.
(2) The installation of measures required in a plan prepared under division (E)(3)(a) above may be certified by the applicant.
(3) The installation of measures required in a plan approved pursuant to division (E) above except division (E)(3)(a) above shall be subject to inspection by the city. The Director may allow the project to be inspected and certified by the engineer or by a geologist who prepared the plan.
(H) Purposes of storm and surface water management. Detention of stormwater collected from impervious surfaces on a given property, or within public rights-of-way, is essential to the management of stormwater in the city. This section includes standards for conveyance of surface water to streams, creeks and channels. It also addresses pollution reduction and flow control for stormwater generated from new and redevelopment. For the purpose of this section, new and redevelopment refers to any human-made change to improved or unimproved real estate including, but not limited to, the placement of buildings or other structures, dredging, filling, grading or paving. This section provides standards for addressing infiltration, treatment and detention of stormwater separately as well as an option for a combined approach to mitigating the water quality impacts of developments that fall below a certain size threshold.
(I) Applicability.
(1) No permit for construction of new development or tenant improvements that results in impervious cover greater than 499 square feet for development activity on any land within the city at the date of an application shall be issued until effects on stormwater management are evaluated. The level of review varies according to the size of the affected area as follows.
500 to 1,999 square feet | No stormwater management measures beyond any mitigation measures for pollution reduction or flow control are required |
2,000 to 4,999 square feet | Conceptual plans shall be submitted for approval |
5,000+ square feet | A comprehensive stormwater management plan shall be submitted for approval |
Areas smaller than 500 square feet may require review, and a greater level of review for properties between 500 and 4,999 square feet may be necessary when the site is identified as having especially sensitive conditions, including but not limited to, wetlands, steep slopes and fish bearing streams | |
(2) Separate applicability thresholds for pollution reduction and flow control standards are listed in division (M) below. Development projects shall not be phased or segmented in such a manner to avoid the requirement of this section.
(3) The Oregon Department of Transportation (ODOT) may require stormwater and water quality management plan coordination, design approval to state standards and applicable permits for all development impacting state transportation drainage facilities.
(J) Stormwater management plan submittal.
(1) Site plans shall include the following analyses and descriptions:
(a) A description of stormwater mitigation strategies to increase infiltration, promote evapotranspiration (use of water by plants) and reduce the amount of stormwater runoff generated from the site;
(b) Calculations of the amount of impervious surface before development and the amount of impervious surface after development. Impervious surface refers only to strictly impervious surfaces including roofs of buildings, impervious asphalt and concrete pavements, and other specifically impervious pavement materials such as mortared masonry and gravel;
(c) An analysis of vegetative and other treatment methods used to reduce pollutants;
(d) An analysis of flow reduction methods including infiltration, detention and retention techniques; and
(e) Statement of consistency with the city stormwater management and, if applicable, the watershed management plan for the basin and/or requirements of a pollutant load reduction plan for a water quality limited stream which may be affected by ground disturbance or increased or altered flow regime.
(2) Post-construction plans shall include the following information:
(a) As-built plans, stamped by an engineer or geologist indicating all stormwater mitigation and management strategies are installed per approved plans and approved changes; and
(b) Maintenance plans for all stormwater treatment facilities installed to comply with this section. The maintenance program shall be subject to a recorded agreement with the city that outlines the stormwater treatment facility responsibilities of property owners and the city.
(K) General requirements.
(1) Intent and purpose. All development shall be planned, designed, constructed and maintained to provide a system by which storm/surface water within the development will be managed without causing damage or harm to the natural environment, or to property or persons and to protect property from flood hazards.
(2) Criteria. Plans shall be submitted to the Planning Department for review. All plans and calculations for areas 5,000 square feet or larger must be stamped and signed by a hydrologist, civil engineer or other similarly qualified person approved by the city. Plan approval will be based on the following criteria.
(a) Design, construction and maintenance of proposed stormwater management plan will result in limiting as much as possible the increase in post-development off-site stormwater flow over pre-development off-site stormwater flow.
(b) All in-stream culvert installations must allow fish passage in accordance with Division of State Lands (DSL) and the US Army Corps of Engineering (COE) and any other authorized federal, state or local agency.
(c) Installation of culverts, spans or stormwater outfalls along natural water features shall be designed to emphasize preservation of natural flow conditions and pursue stream enhancement opportunities.
(d) Stormwater mitigation strategies, such as retention of existing trees, and use of porous paving surfaces, as well as stormwater treatment and flow control facilities used to meet the requirements of this code must be included in the plans.
(e) Stormwater management plan shall be consistent with the city’s most current stormwater engineering practice.
(f) In areas of high pollutant load, stormwater infiltration shall incorporate, or be preceded by treatment as necessary, to prevent siltation of the infiltration facility, protect ground water and prevent toxic accumulations of pollutants in the soil.
(g) All storm conveyance pipes, vaults and stormwater infiltration, treatment and detention facilities shall be built to specifications of the city.
(h) The plan shall demonstrate compliance with the standards of division (L) below.
(i) The plan shall demonstrate compliance standards of division (M) below.
(3) Infiltration facilities. The city may further restrict the use of infiltration facilities in high risk areas including those in natural hazard areas with steep slopes, unstable soils, high water tables or sites known to be contaminated by hazardous substances.
(a) Infiltration facilities. Infiltration facilities which fall under the jurisdiction of DEQ’s Underground Injection Control (UIC) Program must be registered with the state and meet the requirements of the UIC Program.
(b) Security. Applicants shall provide cash or a letter of credit acceptable to the city to assure successful installation and initial maintenance of surface pollution reduction and flow control facilities.
(c) Contingency for system failure. If the storm drainage system fails due to lack of maintenance or breakage, and there are impacts to downstream water quality or quantity as a result of the failure, the city may perform the maintenance or repair and has the authority to charge the owner of the facility.
(L) Surface water conveyance standards. The following measures are designed to efficiently convey stormwater.
(1) Culverts in and spans of streams, creeks, gulches and other natural drainage channels shall maintain a single channel conveyance system.
(2) Culverts and/or spans are to be sized for the 24-hour post-developed tributary conditions of the ten-year storm on streams with an average flow less than 200 cfs.
(3) Conveyance calculations shall use the following methods for analysis:
(a) Projects smaller than 20 acres: the rational method, Santa Barbara Urban Hydrograph, SCS TR-55, HEC-1, or SWMM; and
(b) Projects 20 acres or larger: any of the methods except the rational method. Exceptions must be documented and approved by the city.
(4) Credit will not be given for in-stream and in-line detention.
(5) It shall be the responsibility of the owner that the new drainage system shall not negatively impact any natural water conditions. The owner is responsible for providing a drainage system for all surface water, springs and groundwater on site and for water entering the property, as well as management of springs and groundwater that surface during construction.
(M) Pollution reduction and flow control standards.
(1) Applicability. These standards shall apply to all subdivisions or site plan applications creating greater than 500 square feet of impervious surface or redevelopment footprint area, unless eligible for an exemption or granted a waiver by the city. Additionally, these standards apply to land development activities that are smaller than the minimum applicability criteria if such activities are part of a larger common plan of development that meets the applicability criteria, even though multiple separate and distinct land development activities may take place at different times and at different schedules.
(2) Waivers. The city, at its discretion, can waive in whole or in part minimum requirements for stormwater management; provided the applicant can prove with submitted findings that at least one of the following conditions applies:
(a) It can be demonstrated that the proposed development is not likely to impair attainment of the objectives or standards of this section, the city’s stormwater plan or the city’s stormwater management program;
(b) Alternative minimum requirements for on-site management of stormwater discharges have been established in a stormwater management plan that has been approved by the city;
(c) Provisions are made to manage stormwater by an off-site facility. The off-site facility is required to be in place, to be designed and adequately sized to provide a level of stormwater control that is equal to or greater than that which would be afforded by on-site practices and there is a legally obligated entity responsible for long-term operation and maintenance of the stormwater practice;
(d) The city finds that meeting the minimum on-site management requirements is not feasible due to the nature or existing physical characteristics of a site; or
(e) Non-structural practices will be used on the site that reduce:
1. The generation of stormwater from the site;
2. The size and cost of stormwater storage; and
3. The pollutants generated at the site. These non-structural practices are explained in detail in the current design manual and the amount of credit available for using such practices shall be determined by the city.
(N) Infiltration, treatment and detention. Proper management of stormwater includes a combination of infiltration, treatment and detention. This section establishes the review standards for each method.
(1) Infiltration.
(a) Infiltration systems are to infiltrate a minimum of one-half inch of rainfall in 24 hours.
(b) Stormwater treatment, in accordance with division (N)(2) below shall occur prior to or concurrent with infiltration.
(c) Infiltration systems shall be designed to overflow to conveyance systems.
(d) Infiltration may be waived, or reduced, if it can be demonstrated by an engineer or geologist that infiltration will destabilize the soil, cause structural problems or provide negative impacts to the environment, or because of site constraints such as high groundwater or soil contamination. In such cases, findings shall demonstrate that stormwater runoff will not adversely affect adjacent properties or substantially change the flow characteristics of receiving water ways, or if runoff is determined to occur, the developer shall be responsible for in-lieu-of fees for regional treatment or off-site mitigation.
(2) Treatment.
(a) Water quality treatment facilities shall be designed to capture and treat runoff for all flows up to the ninety-fifth percentile storm event. For design purposes, the ninety-fifth percentile storm event is defined as two and one-half inches of precipitation in a 24-hour period.
(b) The water quality system shall use vegetation for treatment. Alternative systems may be used with approval of the Director after consulting an engineer and shall be designed to provide equivalent treatment as is provided with a vegetated system.
(c) Systems treating stormwater from over 5,000 square feet of impervious area and all systems must be designed by a registered engineer and be approved by the city.
(3) Detention. On-site storm quantity detention facilities shall be designed to capture and detain runoff as follows:
(a) Two-year, 24-hour, post-developed runoff rate to a two-year, 24-hour pre-developed discharge rate; for design purposes, a two-year, 24-hour storm is defined as five inches in a 24-hour period; and
(b) Sites with infiltration systems designed to handle storms in excess of that specified in division (N)(3)(a) above will be permitted to reduce on-site detention requirements by a volume equal to 100% of the infiltration capacity.
(4) Conveyance. Infiltration, treatment and detention facilities shall be constructed to convey excess stormwater. Conveyance systems shall be sized to meet the following conditions:
(a) Stormwater drainpipes draining less than 640 acres: 25-year, 24-hour design storm; and
(b) Stormwater drain pipes draining greater than 640 acres: 50-year, 24-hour design storm.
(O) Plan review and approval requirements. All plans submitted pursuant to this section must be reviewed and approved by the Director prior to completing applicable development.
(Ord. 1263, passed 7-5-2011; Ord. 1265, passed 7-5-2011; Ord. 1267, passed 1-3-2012)