Administrative Rule Adopted by Bureau Pursuant to Rule-Making Authority
1. Sanitary Sewer Review Criteria. Technical decisions of adequacy of a development proposal are judged on the following three criteria (some of these criteria are the same for storm sewer systems):a) Location. Technical review should ascertain whether the location of the proposed sanitary sewer meets all the requirements of the Sewer Design Manual as well as natural resource requirements. The first question to be addressed is whether there is a public sewer line available to extend to the site.(1) Service Provision Requirements (section 12-1). The system shall collect sewage from lowest floors of all planned buildings through gravity service where practicable.(2) Sewer Service Line Design (section 13-1). The system shall collect sewage in a separate line for each building.(3) Sewer Locations (section 14-1). Locations are based primarily on accessibility for construction, maintenance and service needs. In general, the system shall be located at a sufficient distance from structures, other underground utilities, and other obstructions to reduce construction and maintenance hazards. Existing facilities must either be in an easement or provide some other assurance of adequate maintenance.(4) Sewer Easements (section 15-1). All City owned sewers shall be located in the public right-of-way, in dedicated easements, or specifically dedicated on the final plat. BES must approve of all easement locations and will be responsible for notifying Right-of-Way Acquisition staff in the Office of Transportation. Sewers may not be constructed on private property until an easement or a right-of-entry is acquired. Off-site easements are required prior to permitting or approval of the final plat. Public projects must be signed over to the City prior to a Certificate of Completion for the sewer. Easements shall in general:(a) Avoid splitting or angling across property; and(b) Avoid damage or natural resources; and(c) Avoid future impediments (i.e. retaining walls or plantings); and(d) Be located as far as practicable away from buildings (sewer construction should not endanger building footings); and(e) Be exclusively used for sewers. Footings, roof overhangs, and other utilities (unless expressly permitted by BES) are not allowed in easements; and(f) Be recorded in the name of the City and signed by the legal property owners of record.
All easements will be recorded by the City against the property deed and accepted by City Council Ordinance.(5) Sewer Alignments (Section 16-1). Sewer alignments are determined primarily by the need to provide gravity service; and secondarily by maintenance considerations, preservation of environmentally zoned areas, and the need to reserve space in rights-of way or streets for other utilities. All sanitary and storm sewers, including culverts, must be:(a) Designed on straight horizontal and vertical alignments between bottoms of manholes or other access points, when practicable; and(b) Parallel to curbs, street center lines, property lines and/or easement lines, when practicable; and(c) A blind bend or curved horizontal alignment may be allowed where the straight alignment will result to a moderate or major impediment to construction or maintenance – for examples in cases where soil stability or step slopes are a major design issue.(d) Culverts are located with their ends perpendicular to the right-of-way to provide for a straight street crossing.(6) Sewer Depths (Section 17-1). Depths are determined by service and maintenance needs, depths of existing sewer connection, depths of other utilities, economy, pipe strength limitations and the need to protect the sewer from surface influences. In general they shall be deep enough to provide gravity service from the building and shall adequately clear existing and future utilities.(7) DEQ Requirements (section 21-1). All non-gravity sewers, sewage treatment works, or sewage disposal systems must be submitted to and approved by the Oregon Department of Environmental Quality (DEQ).(8) Underground Utility Investigation and Coordination (section 10-1). The applicant designer is responsible for investigating the location of existing and proposed underground utilities during the design process.b) Capacity.(1) Sewer Hydraulic Design (section 20-1). Designers must use the Sewer Design Manual charts for roughness co-efficient and to address energy losses within the pipe.(2) Quantity of Wastewater (section 22-1). Sanitary sewers must be designed to carry the present and future wastewater flows (based on future Comprehensive Plan zoning). The design shall address flows from the total drainage basin minus the area of the street right-of-way, parks, cemeteries, and other such areas. Flows must be considered from other jurisdictions.c) Easements/ Drainageway Reserves. Are there easements or drainage reserves already present that would influence site design? Other than pipe easement described in (4) above, applications may be required to obtain a drainageway reserve. See Other Administrative Rules below for new rules on sizing and approving improvements on drainageways.2. Stormwater Management Review Criteria. Technical decisions on adequacy of a development proposal are judged on the following seven criteria:a) Policy. The proposed development must meet the stormwater management control policies specified in Section 23-1 of the Sewer Design Manual:(1) Discharge at the natural location. Drainage through a natural basin or sub-basin, whether naturally occurring or from a proposed project site, must be discharged to a natural location. Other locations may be approved for discharge in an effort to preserve natural resources. Diversions to correct an existing drainage problem are variances to this policy. Discharges must:(a) Produce no significant impacts to downstream property; and(b) Be discharged through an acceptable conveyance or discharge point; and(c) Be discharged to a proper outfall or treatment facility that can demonstrate no impact to downstream properties and that will not deteriorate due to velocities and quantity of water discharged within the design storm event.(2) Off-site analysis. Projects must identify the upstream tributary drainage area and shall include a downstream analysis. For major sub-divisions, the analysis must extend downstream of the project location to a point in the drainage system where the project only constitutes 15% of the total drainage area. This point shall not be less than 1,500 feet downstream from the project location.(a) Exemption. If the new impervious area is less than 5,000 square feet or if the upstream drainage area is less than 5,000 square feet, then adequate protection is assumed to be provided by the existing system.(3) Runoff Control. This section of the Sewer Design Manual is superceded by the most recent version of the Stormwater Management Manual (SWMM) – except where the approved point of discharge has limited capacity.(4) Conveyance System. All conveyance systems for proposed projects must be analyzed, designed and constructed for existing tributary off-site runoff, developed on-site runoff from the project, and anticipated tributary drainage from full buildout. Systems must:(a) Convey the peak runoff rate for the 10-year storm event, plus existing upstream runoff that is conveyed through the project site. Designs must account for the actions of the 100 year storm event on the site; and(b) Contain the runoff within a defined conveyance system; and(c) Not damage any buildings due to flood waters; and(d) Convey any overland flow through a drainageway in a reserve or easement.(5) Erosion/Sediment Control Plan. This section of the Sewer Design Manual is superceded by Title 10 requirements and BES contract specifications.(6) Operation and Maintenance. This section of the Sewer Design Manual is:(a) Superceded by the most recent version of the Stormwater Management Manual (SWMM) for stormwater management facilities; or(b) Superceded by the 1997 Surface Stormwater Facilities Maintenance Management Manual for pipe inlets, leads, culverts, drainage ditches, and outfalls associated with stormwater conveyance.b) Discharge. Discharge review requires projects to determine if public system service is available and whether or not extension of a public system is required to support the development. Where is the point of discharge? Is there sufficient capacity in this receiving facility or system for the anticipated amount of discharge?c) Location. Projects must demonstrate that there is adequate room to support the facility and that the facility is located appropriately for the site and for access for operations and maintenance. The following maps and resources are reviewed and evaluated to determine appropriateness:(1) Overlay maps. To assure there is access to service locations, if specific zoning overlays of concern are present (E-zones, etc) and that site is not impacted by local geological features. Further geotechnical information may be required.(2) Topographic maps or Site Analysis Geotechnical reports are used for slope determinations and to determine whether slope will effect facility effectiveness.(3) Geotechnical maps. Geotechnical maps, Site Analysis reports or City soils staff recommendations are used to determine soil infiltration rate. Site-specific reports are required for sites where a public sump is proposed. The Bureau of Development Services (BDS) must approve all onsite disposal systems.(4) Proposed site plans. Proposed site plans to assess:(a) The amount of impervious area generated runoff that the site needs to manage; and(b) The predevelopment ground cover conditions. The project will be evaluated for impacts to natural resources (trees) within the project disturbance area; and(c) The impacts from the configuration of the development. Review occurs at this stage to note if there are e-zone protection issues that would require additional permitting and review; and(d) Type of stormwater management facility proposed and whether adequate space for said facility is provided; and(e) Compliance with the SWMM for:(i) General public health and safety issues; and(ii) Facility setbacks from buildings, property lines and natural resources.(5) Site map. Site maps are used to ascertain whether the project location is likely to trigger state or federal permits.d) Type. Reviewers will determine whether the type of facility is appropriate based on reviewing the following:(1) Soil Type. Staff review site technical reports to determine if infiltration capabilities of the site. Will review to assure that the soil type and structure will support the proposed stormwater management feature.(2) Topography/Geologic Features. Staff review overlay maps to determine if there are any natural formations that would limit effectiveness of stormwater facilities.(3) Regulatory Requirements. Staff review overlay and site maps to determine if any zoning overlay, basin specific, state or federal requirements would need additional permitting and review.(4) SWMM Requirements. Staff general review for compliance with the SWMM standards for facility sizing, facility geometry, facility landscaping (if landscaping plan provided at the land division stage), facility setbacks, and general facility safety and design features.e) Capacity. Proposed facilities must meet the stormwater management and stormwater conveyance requirements in the SWMM and Sewer Design Manuals.(1) Facility Type. The type of proposed facility is evaluated against the stormwater pollution removal, flow control, infiltration/disposal, and in facility conveyance requirements of the SWMM.(2) Conveyance System. Pipes, culverts, ditches and open drainageways are reviewed against standards in the Sewer Design Manual. These conveyance systems must meet the following requirements:(a) Quantity (section 24-1). All systems must be designed to pass the appropriate design storm without surcharge and without damage to property or endangering human life or public health. Storm sizes vary upon the type of downstream receiving system.(b) Storm Frequency (section 26-1). Facilities must be designed to meet the minimum design storm size with the overflow route of stormwater runoff addressed in the overall site design. The design must demonstrate that the 100-year flood shall be passed, in such a way as, to prevent extreme property damage or danger to human health. Less frequent, more intense design storms may be required for use under the following conditions:(i) No overland route is available to carry runoff if the facility is flooded; or(ii) Facility flooding would interfere with high volume or high speed traffic corridors; or(iii) Facilities are in a commercial district with basements containing expensive merchandise easily damaged by water at an elevation that could reasonably be flooded; or(iv) Culverts or other facilities where overflow of the roadway could cause erosion and the loss of roadfill and pavement; or(v) Combined sewer areas where surcharging would result in flooded basements that endanger public health; or(vi) Detention basins where overtopping of the basin would cause property damage or endanger life; or(vii) There is a threat of loss of life might result due to hydraulic overloading conditions. Then the 100-year storm size or the probable maximum precipitation size shall be used (detention basins and culverts under roadfills are the most likely to trigger this condition).(c) Rainfall Intensity (section 27-1). For the purposes of developing “design storms” the rainfall intensity is measured as a peak intensity rather than from its beginning. Intensities vary depending on geographical location:(i) Portland International Airport storms. Areas north and east of the Tualatin Mountain Range.(ii) Fanno Creek Study Area storms. Areas south and west of the Tualatin Mountain Range crest.Sewer Design Manual IDF curves (Chart 11-24) must be used when designing using the rational method.(d) Time of Concentration (section 28-1). This design calculation is measured from the peak of the storm. Inclusion of “wetting time” is not permitted.(e) Runoff Coefficients (section 29-1). Use Sewer Design Manual Chart 10.(f) Area of Drainage Basin (section 30-1). The drainage area must include the entire area that will drain to a point of interest when the proposed development is complete. Drainage areas are generally delineated using maps. Flat drainage areas must be field reviewed. Any proposal to switch the basin of the sites receiving flow must include a complete analysis for approval by the BES Chief Engineer.f) Offsite connections. Staff will review existing system records to determine the capacity for offsite public conveyance systems. Additional analysis by applicant may be requested to assure sufficient ability to use an offsite system.g) Program coordination. Proposals will be reviewed for impact on other City projects and City programs. If a linkage is detected, additional analysis or management may be required depending on specific project or program need.
1. Impacts to Natural Resources. Staff reviewers assess how the proposed development will impact the resources of the specific site and the overall watershed. Staff review for impacts against the following factors:a) Wetlands. Reviewers note wetlands or suspected wetlands located on the project site; andb) Streams, Seeps and Springs. Reviewers note the predevelopment natural drainage patterns and then comment on the significance of impact from the proposed development; andc) Development Configuration. Reviewers assess whether the proposed development is configured to minimize environmental impact and avoid aggravating any flooding problems. Elements such as clustered development, minimizing impervious surfaces, and retaining natural vegetation and trees are all desired development components; andd) Vegetative Cover. Reviewers assess the level of impact on existing trees and vegetation and assess the appropriateness of mitigation related vegetation. Multi-storied canopy area, variety of native plant species, and connectivity of vegetation to surrounding resource areas are all desirable development traits; ande) Topography / Geologic Features. Reviewers note any special site geography related elements that should be considered in the site design. Elements such as large rock outcroppings and very steep terrain are common notations; andf) Soil Type. Reviewers will note location of poorly infiltrating soils or areas that are likely to be susceptible to erosion. Enhanced erosion control measures are often recommended; andg) Facility Type. Reviewers will note if the facility type does not seem protective of environmental resources. In general surface vegetated facilities and features that enhance resource area values are preferred –although are not necessarily required; andh) Natural Resource Assessments. Reviewers identify environmental resources on the site that are not already located within environmental overlay zones. If the resources are significant, the reviewer recommends that they be placed in a preservation tract. Reviewers evaluate the site proposal against the current resource values and functions of the site. Modifications to site design and construction elements are recommended; andi) Watershed Specific Goals. Reviewers will also note watershed specific goals that may apply. For instance, recommending enhanced canopy cover in areas that have been designated tree deficient in watershed assessments or trying to limit effective impervious areas in sensitive basins; andj) Site Visits. Reviewers may determine that a staff site visit is necessary to further familiarize themselves with the site. Site visits will be conducted by watershed staff as needed on a case-by-case basis.2. Site Location. Reviewers will note any other special non-City regulations that pertain to the proposed development site. Staff review against the following regulations and or impact areas:a) Environmental, Greenways or Open Space Zones. Reviewers note concerns with certain activities within these resource oriented overlay zones; andb) State or federal regulations. Reviewers often consult with Endangered Species Act, Office of Sustainable Development and other agency or jurisdictional staff to determine impacts and concerns related to the site development. Typical regulations include:(i) COE/DSL Permits. Instream work or wetland fills are subject to a joint permit from the Army Corp of Engineers and the Department of State Lands.(ii) FEMA. Reviewers assess whether Federal Emergency Management Agency flood plain regulations or the Community Rating System (CRS) criteria apply to the development.c) Stewardship Efforts. Reviewers note the ability to assist developers in enhancing their sites through environmental stewardship activities. The most commonly mentioned is participation with the BES Revegetation Program to restore and enhance local streambank or upland areas that are within the development site.3. Site History. Reviewers note any past event knowledge, such as propensity to flood or prior landslide issues.
1. System type. Staff review to determine the nature of the receiving system and whether it will receive any treatment prior to discharge.2. Locations and services. Staff review the proposal to determine whether a private outfall or connection to the City sewer is proposed where a City or State discharge permit may be required.3. Site history. Reviewers assess the potential for historical contamination of the site. Staff review the DEQ permit and City Source Control databases for signs of permits and/or complaint responses to the site.4. Other city resources. Reviewers assess whether other City regulatory programs have information available on this site. Sources include the City’s Municipal Stormwater NPDES and Treatment Plant (POTW) NPDES permit documents.5. Activities and design of site. Reviewers ascertain whether post development activities on the proposed site will trigger regulatory requirements. Staff work with the developer to evaluate whether future site operations will have materials or wastes exposed to rainfall or stormwater runoff or whether a concentrated discharge to the storm or sanitary sewer systems is likely.6. Local, state, and federal requirements. Reviewers are specifically responsible for:a) Reviewing for compliance with the Pollution Controls elements within the SWMM (chapter 4); andb) Reviewing for compliance with other industrial related sections of City code (i.e. Titles 17.34, 17.36, 17.39); andc) Evaluation of other permits that may be applicable (i.e. Water Pollution Control Facility permits for sumps and other groundwater injection systems); andd) Identification and assessment of future site activities and their potential to raise compliance issues with other State Department of Environmental Quality regulations.
1. Information packets submitted to BES shall include the name and contact information of the interested party and a date of packet submittal; and2. Submittals shall include the name and/or address of the proposed development; and3. Interested parties shall submit a cover letter of no more than one page in length that highlights the topics and issues on which further information will be provided; and4. Submittals shall include a one page summary of discussion for each topic / issue. This discussion shall detail the relevance of the supplied information on the project and the desired outcome and/or response to be made by BES. Additional pages of background material may be submitted. The BES staff person is not obligated to review this background material unless they will incorporate it into their review; and5. Interested parties are encouraged to submit photos, maps, drawings or other materials that support the issues raised in the submittal; and6. BES shall respond to the interested party within one week to confirm the receipt of the submittal; and7. BES shall copy or otherwise notify the interested party or parties on the resolution to the project review, and explain how this additional information was incorporated into the BES application review comments.
1. Historic conditions. Including old site use, historic flood levels, old seeps/springs, etc.; and/or2. Site constraints. Including direct knowledge of site specific issues like slopes, slide hazards, water table, habitat usage, etc; and/or3. Other relevant topics. BES in general will not consider alternative engineering or design submittals that challenge the technical calculations or professional judgments used in sizing proposed facilities.
BES Chief Engineer
1120 SW 5th Avenue, Room 1000
Portland, OR 97204-1912
Fax (503) 823-7761
(1) Definition. Drainageway is an open linear depression, whether constructed or natural, which functions for the collection and drainage of surface water. It may be permanently or temporarily inundated.(2) Drainageway Reserves. A drainageway reserve shall be placed to assure adequate and environmentally beneficial conveyance of stormwater across a developing site. Because of the unpredictable nature of storm events and great variation in potential flows, the sizing of drainageway reserves does not guarantee prevention of damages in all situations. Requirements imposed by the Bureau of Environmental Services are designed to address typical flows and do not relieve property owners of their responsibility to manage stormwater in a manner that complies with the duties of property owners under applicable law. Reserves shall be placed on a proposed development site in one of the following manners:(a) 15 feet from the centerline of the channel; or(b) 15 feet from the delineated edge of a designated water feature (i.e. seep, spring, wetland); or(c) Within the boundary of a designated environmental zone; or(d) Over a designated seep, spring and stream tract.Exemptions: Drainage reserves shall not be required for drainageways located within a FEMA designated and mapped area.(3) Sizing of Drainageway Reserves. Drainage reserves shall be sized to assure that the current flow rate and pattern of the drainageway continues to be adequately conveyed through the development site. Current flow volumes and/or drainageway capacities will be determined by:(a) Reviewing existing data, which may include available hydrologic records, drainage basin hydrology, historical data, high water marks, soil inundation records, photographs of past flooding, and other similar information.(4) Improvements within Drainageway Reserves. Improvements within the drainageway reserve shall only be approved when all of the following conditions exist:(a) Where the modification will not impede or reduce flows within the drainageway; and(b) Where the improvement will enhance the surface flow capacity and habitat values of the drainageway; and(c) Where the improvement shall provide additional safety to public or privately held properties or facilities; and(d) Where the improvement is constructed with minimal hard surface armoring of the drainageway.(5) Improvement Development Standards: All improvements shall meet one of the following development standards:(a) All improvements shall comply with City codes and standards that apply to the improvement being proposed (i.e. erosion control manual, street design standards, and Sewer Design Manual); or(b) Other design guidelines may be used, but only if approved by the BES Chief Engineer.
Appendix A - June 6, 2002 Authorizing Ordinance