This manual and design standards with all future amendments and revisions shall be known as the Stormwater Management Manual (herein referred to as the manual or SWMM).
(Res. 40-08 (§ 201), 3-19-08)
This manual and design standards shall apply to all new development and redevelopment within the boundaries of Mesa County, including any public lands, facilities constructed on rights-of-way, easements dedicated for public use, and to all privately owned and maintained drainage facilities, including but not limited to detention ponds, storm drains, inlets, manholes, culverts, swales, channels and water quality facilities.
(a)
Mesa County.
Chapter 7.7 of the Mesa County Land Development Code (Code) requires that “Drainage facilities shall be designed and installed in accordance with the Mesa County Stormwater Management Manual.”
(b)
City of Grand Junction.
The City of Grand Junction Zoning and Development Code (GJMC Title 21) requires that “All proposed development must provide for on-site runoff collection and conveyance in accordance with the Stormwater Management Manual (SWMM) and applicable federal and State laws.”
The City of Grand Junction adopted stormwater pollution prevention Ordinance Number 3824 (Chapter 13.28 GJMC), which requires that: “All proposed development … must provide for on-site erosion and sediment control, control of illegal discharges, and runoff collection and conveyance in accordance with the Stormwater Management Manual and applicable federal and State laws.”
(c)
Other Jurisdictions.
The City of Fruita, the Town of Palisade, and the Grand Junction Drainage District may adopt the Stormwater Management Manual in whole or in part.
(Res. 40-08 (§ 202), 3-19-08)
(a)
Municipality.
Powers to regulate land use activities, including drainage, are granted to a municipality under Colorado Revised Statutes as noted below:
§ 31-15-701, C.R.S. et seq. grants municipalities the power to establish, improve, and regulate such improvements as streets and sidewalks, water and water works, sewers and sewer systems, and water pollution controls. In addition, a municipality may, among other powers, deepen, widen, pipe, cover, wall, alter or change the channel or watercourses.
§ 31-25-501, C.R.S. et seq. authorizes municipalities to construct local improvements and assess the cost of the improvements wholly or in part upon property specially benefited by such improvements. By ordinance, a municipality may order construction of district sewers for storm drainage in districts called storm sewer districts. (For the City of Grand Junction, see People’s Ordinance No. 33.)
§ 31-25-601, C.R.S. et seq. authorizes municipalities to establish improvement districts as taxing units for the purpose of constructing or installing public improvements.
§ 31-35-401, C.R.S. et seq. authorizes municipalities to operate, maintain, and finance water and sewage facilities for the benefit of users within and without their territorial boundaries. Sewerage facilities are defined as “any one or more of the various devices used in the collection, treatment or disposition of sewerage or industrial wastes of a liquid nature or storm, flood or surface drainage waters….”
(b)
County.
Powers to regulate land use activities, including drainage, are granted to a county under Colorado Revised Statutes as noted below:
§ 24-67-101, C.R.S. et seq. (Planned Unit Development Act of 1972) power to encourage more efficient and innovative use of the land for public services and encourages integrated planning.
§ 29-20-101, C.R.S. et seq. (Local Government Land Use Control Enabling Act of 1974) clarifies and provides broad authority to local governments to plan for and regulate the use of land within hazardous and environmentally sensitive areas.
§ 30-20-401, C.R.S. et seq. authorizes construction, maintenance, improvements and financing of water and sewerage facilities for the County’s own use and for the use of the public and private consumers and users within and without the County’s territorial limit.
§ 30-20-501, C.R.S. et seq. (County Public Improvement District Act of 1968) authorizes creation of public improvement districts within any county as taxing units and for the purpose of implementing public improvements.
§ 30-20-601, C.R.S. et seq. authorizes a county by resolution to construct local improvements and to assess the costs to properties especially benefited by improvements.
§ 30-28-101, C.R.S. et seq. provides the County with planning authority, such as development of master plans and adoption of such plans by resolution; creation of a regional planning commission; and regulation of development density.
§ 30-30-101, C.R.S. et seq. (control of stream flow) provides power to remove any obstruction to the channel of any natural stream which causes a flood hazard and provides a right of access to any such natural stream.
(Res. 40-08 (§ 203), 3-19-08)
(a)
Mesa County.
The Director or an authorized representative is responsible for enforcing the provisions of this manual.
(b)
City of Grand Junction.
The City Manager or the City Manager’s designee is responsible for enforcing the provisions of this manual.
(c)
Other Jurisdictions.
Contact the City of Fruita, the Town of Palisade, or the Grand Junction Drainage District for information.
(Res. 40-08 (§ 204), 3-19-08)
All drainage submittals will be reviewed for general compliance with this manual. An acceptance does not relieve the owner, engineer, or designer from responsibility of ensuring that the calculations, plans, specifications, construction, and record drawings comply with this manual.
Adequate time must be allocated in development planning to permit a complete review. The intent of this manual is to more clearly define the requirements and reduce the time and effort required to develop an acceptable drainage design.
(a)
Mesa County.
Acceptance of final drainage report and drainage facility construction plans shall be valid for two years. Documents with approvals more than two years old may require revision prior to development to comply with the provisions of the manual in effect at that time. Amendments to this manual will apply to all drainage reports submitted after the effective date of the amendment. Final drainage reports are exempt from an amendment provided they are submitted for approval within 60 days after the effective date of an amendment.
(b)
City of Grand Junction.
Drainage submittals shall contain all information required by this manual but the review process will be in accordance with the City’s Submittal Standards for Improvements and Development (SSID) and the Zoning and Development Code (GJMC Title 21).
(c)
Other Jurisdictions.
Contact the City of Fruita, the Town of Palisade, or the Grand Junction Drainage District for information.
(Res. 40-08 (§ 205), 3-19-08)
In the interpretation and application of the provisions of the manual, the following shall govern:
(a)
Minimum Standards.
This manual shall be regarded as the minimum requirements for analysis and design of storm drainage facilities. Special site conditions or mitigation for potential impacts from new development or redevelopment may result in more stringent standards.
(b)
Higher Standards.
For Mesa County if provisions of the code, any law, ordinance, resolution, rule, or regulation contains restrictions covering the same subject matter, the more stringent standards or requirements shall govern. For the City of Grand Junction if provisions of the Zoning and Development Code (GJMC Title 21), any law, ordinance, resolution, rule, or regulation contains restrictions covering the same subject matter, the more stringent standards or requirements shall govern.
(c)
Flexibility.
There may on occasion be need for site-specific application and interpretation of this manual. The Director in Mesa County or the City Manager or the City Manager’s designee in the City of Grand Junction may deviate from the requirements of this manual; provided, that the approved plan is compatible with surrounding in-place improvements and is sufficiently protective. The burden of responsibility shall be on the applicant to show that the requested deviation/variance from standards does not create a public hazard.
(d)
Abrogation.
This manual shall not abrogate or annul any permits or approved drainage reports, construction plans, easements, or covenants issued before the effective date of this manual.
(Res. 40-08 (§ 206), 3-19-08)
(a)
Deviations/variances from specific standards, procedures, or criteria in this manual may only be requested for:
(1)
Unusual situations where strict compliance with the manual may not protect the public health and safety; or
(2)
Unusual situations which require additional analysis outside the scope of the manual for which the additional analysis shows that strict compliance with the manual may not protect the public health and safety; or
(3)
Unusual hydrologic and/or hydraulic conditions which cannot be adequately addressed by strict compliance with the manual.
(b)
Mesa County.
A variance from the technical provision of this manual may be granted by the Director. All requests for variances shall be submitted in writing (normally with the drainage report, see Chapter 28.12 GJMC), shall state the provision for which the variance is requested, and shall provide evidence, data or other information in support of the request. The Director will review and rule on the request and provide his findings in writing.
(c)
City of Grand Junction.
A deviation from any requirement of this manual may be granted by the City Manager or the City Manager’s designee. A request for deviation shall be submitted in writing as a separate letter attached to the drainage report. The request shall state the provision for which the deviation is requested and shall provide supporting evidence, data, or other appropriate information. The City Manager or the City Manager’s designee shall review and rule on the request and provide the findings in writing.
(d)
Other Jurisdictions.
Contact the City of Fruita, the Town of Palisade, or the Grand Junction Drainage District for information.
(Res. 40-08 (§ 207), 3-19-08)
The following acronyms are used within the context of this manual:
BMP | Best Management Practice |
CAP | Corrugated Aluminum Pipe |
CAPA | Corrugated Aluminum Pipe Arch |
CMP | Corrugated Metal Pipe |
CMPA | Corrugated Metal Pipe Arch |
CDOT | Colorado Department of Transportation |
CDPHE | Colorado Department of Public Health and Environment |
CDPS | Colorado Discharge Permit System |
CRS | Colorado Revised Statutes |
CSP | Corrugated Steel Pipe |
CSPA | Corrugated Steel Pipe Arch |
CSWMP | Construction Stormwater Management Plan |
CWA | Clean Water Act |
CWCB | Colorado Water Conservation Board |
EC | Erosion Control |
ECP | Erosion Control Plan |
EGL | Energy Grade Line |
EPA | Environmental Protection Agency |
FEMA | Federal Emergency Management Agency |
GIS | Geographic Information System |
HDS | Hydraulic Design Series |
HEC | Hydrologic Engineering Center or Hydraulic Engineering Circular (FHWA) |
HERCP | Horizontal Elliptical Reinforced Concrete Pipe |
HGL | Hydraulic Grade Line |
MS4 | Municipal Separate Storm Sewer System |
NAVD | North American Vertical Datum |
NFIP | National Flood Insurance Program |
NOAA | National Oceanic and Atmospheric Administration |
NRCS | Natural Resource Conservation Services, formerly the SCS |
NPDES | National Pollutant Discharge Elimination System |
NWS | National Weather Service |
PE | Professional Engineer licensed by the State of Colorado |
PMF | Probable Maximum Flood |
PVC | Polyvinyl Chloride |
RCBC | Reinforced Concrete Box Culvert |
RCP | Reinforced Concrete Pipe |
ROW | Right-of-Way |
SCS | Soil Conservation Service |
SPP | Structural Plate Pipe |
SSID | Submittal Standards for Improvements and Development (City of Grand Junction) |
SWMM | Stormwater Management Manual |
SWMP | Stormwater Management Plan (either the construction SWMP or the final drainage report containing post-construction BMPs) |
TAC | Technical Advisory Committee |
TRC | Technical Review Committee |
UDFCD | Urban Drainage and Flood Control District (Denver, Colorado) |
USACE | United States Army Corps of Engineers |
USBR | United States Bureau of Reclamation |
USDCM | Urban Storm Drainage Criteria Manual, prepared by the Urban Drainage and Flood Control District in three volumes |
USGS | United States Geological Survey |
WQCD | Water Quality Control Division of the Colorado Department of Public Health and Environment |
WQCV | Water Quality Capture Volume |
(Res. 40-08 (§ 208), 3-19-08)
means a qualified agent, individual or firm acting on behalf of the owner of property requesting approval of plans for new development and redevelopment.
Mesa County, the Cities of Grand Junction and Fruita, the Town of Palisade, and the Grand Junction Drainage District have contracted through intergovernmental agreements (IGA) to form the 5-2-1 Drainage Authority (Authority), under Colorado Revised Statutes, specifically § 29-1-204.2, C.R.S.
means schedules of activities, prohibitions of practices, maintenance procedures, and other management practices to prevent or reduce the pollution of State waters. BMPs also include treatment requirements, operating procedures and practices to control site runoff, spillage or leaks, sludge or waste disposal, or drainage from raw material storage.
means a permit issued by the State of Colorado under Part 5 of the Colorado Water Quality Control Act that authorizes the discharge of pollutants to waters of the State, whether the permit is applicable to a person, group or area.
means a natural or artificial low-lying area with a definite bed and banks, which confines and conveys continuous or periodic flows of water. (Mesa County Land Development Code Section 12.1 and GJMC § 21.10.020, Terms defined.)
means any business, trade, industry or other activity engaged in profit.
includes clearing, grubbing, filling, grading, and excavation. Does not include routine maintenance performed by public agencies, private parties, or their agents to maintain original line and grade, hydraulic capacity, or original purpose of the facility. Also see Land disturbance. [(Adapted from CDPS General Permit No. COR-030000 @ Part I A(2)(a)]
means any location where construction or construction related activity occurs.
means a specific individual construction plan that describes the BMPs to be implemented at a site to prevent or reduce the discharge of pollutants during construction activities.
means the Mesa County Planning Director or designee when referring to a Mesa County official, but the City Manager or his designee when referring to a City of Grand Junction official.
means the addition or release of any pollutant, stormwater, subsurface, groundwater or any substance whatsoever to the storm drainage system.
refers to locations which are hydraulically lower in elevation than the location at which the comparison is being made. Downstream may include locations outside of the stream, channel, pipe, etc., such as sheet flow, which often meanders in several directions.
means any natural or artificial (manmade) channel which provides a course for water flowing either continuously or intermittently to downstream areas.
means when all soil disturbing activities at the site have been completed, and uniform vegetative cover has been established with a density of at least 70 percent of pre-disturbance levels, or equivalent permanent, physical erosion reduction methods have been employed. For purposes of the construction SWMP, establishment of a vegetative cover capable of providing erosion control equivalent to pre-existing conditions at the site will be considered final stabilization.
means a temporary rise in a watercourse, flow, or stage, that results in water overtopping its banks and inundating areas adjacent to the channel. (Mesa County Land Development Code Section 12.1; see also GJMC § 21.10.020, Terms defined.)
means the portion of Mesa County whose boundary is approximated by the 5,000-foot elevation contour and extends west of the community of Mack, along the north eastern edge of the Colorado National Monument, south of Whitewater, to the east of Palisade, and along the face of the Bookcliffs to the north.
means a manmade change in the existing cover or topography of the land, including grading, excavation, filling, building, paving, and other activities that may result in or contribute to soil erosion or sedimentation in the discharge of pollutants.
means a detention and/or water quality facility that has been sized based on the area and imperviousness of the watershed that includes all the development that drains to the facility, but is not publicly owned and maintained. Also see Regional facility and On-site facility.
within the context of the SWMM, means Mesa County, City of Grand Junction or Fruita, Town of Palisade, or the Grand Junction Drainage Authority.
means a stormwater facility, such as a channel, large conduit, detention or retention, which receives storm runoff from a watershed generally 160 acres in size or larger.
means a conveyance or the system of conveyances, including roads with drainage systems, municipal streets, curbs, gutters, ditches, drainage inlets, catch basins, pipes, tunnels, culverts, channels, detention basins and ponds owned and operated by a municipality or county and designed or used for collecting or conveying stormwater that is not a combined sewer or used for collecting or conveying sanitary sewage.
For Mesa County definition, refer to the Mesa County Land Development Code. For the City of Grand Junction definition, refer to GJMC Title 21, Zoning and Development. For the City of Fruita, Town of Palisade and the Grand Junction Drainage District definitions, refer to the applicable development codes.
means the National Pollutant Discharge Elimination System under Section 402 of the Clean Water Act.
means a local facility that is contained within and only serves the development in question and not other developments.
means the drainage system typically consisting of swales, curb and gutter, storm drains, and sometimes small open channels that discharge to a major drainage system. Also called “local drainage system.”
means a person having dominant and/or servient interest in property, having sufficient interest to convey property, and/or having possessory interest in property. The term owner also includes the owner’s agent.
means a contiguous area where multiple separate and distinct construction activities will take place at different times on different schedules under one plan. An example would be a commercial development with multiple separate buildings constructed over the course of multiple construction schedules.
means dredged spoil, dirt, slurry, solid waste, incinerator residue, sewage, sewage sludge, garbage, trash, chemical waste, biological nutrient, biological material, radioactive material, heat, wrecked or discarded equipment, rock, sand, or any industrial, municipal, or agricultural waste. [§ 25-8-103(15), C.R.S.]
means the alteration of the physical, thermal, chemical, or biological quality of, or the contamination of any water that renders the water harmful, detrimental, or injurious to humans, animal life, plant life, property or public health, safety or welfare, or impairs the usefulness or the public enjoyment of the water for any lawful or reasonable purpose.
means the final drainage report, in accordance with GJMC § 28.12.060 through 28.12.110, final drainage report, which includes a combination of structural and/or nonstructural BMPs, further described in Chapter 28.64 GJMC, Post-Construction Stormwater Management, that reduce the discharge of pollutants after construction is complete.
means conditions that existed as of the adoption date of this manual.
means all privately owned ground, surfaces, structures or systems, excluding the MS4, that contribute to or convey stormwater including but not limited to roofs, gutters, downspouts, lawns, driveways, pavement, roads, streets, curbs, gutters, inlets, drains, catch basins, pipes, tunnels, culverts, channels, detention basins, ponds, draws, swales, streams and any ground surfaces.
means any improvement, facility or service together with its associated public site, right-of-way or easement necessary to provide transportation, drainage, public private utilities, parks or recreational, energy or similar essential services. (Mesa County Land Development Code Section 12.1.)
means a qualified person, as defined by GJMC § 13.28.010, with specialized training, education, or experience in the field of erosion control methods, planning, and inspection.
The recurrence interval corresponds to the statistical return period of an event of the same intensity (e.g., a 100-year recurrence interval flood has a one percent chance to occur each year, which does not mean that it will occur every 100 years).
means a detention and/or water quality facility that is publicly owned and maintained and serves all properties within the tributary watershed.
means soil, mud, dirt, gravel and rocks that have been disturbed, eroded and/or transported naturally by water, wind or gravity and/or mechanically by any person, vehicle or equipment.
include but are not limited to: raw materials; fuels; materials such as metallic products; hazardous substances designated under Section 101(14) of CERCLA; any chemical the facility is required to report pursuant to Section 313 of Title III of SARA; fertilizers; pesticides; and waste products such as ashes, slag and sludge that have the potential to be released with stormwater discharge.
means all surfaces, structures and systems that contribute to or convey stormwater including private drainage systems and the MS4, and any nonmunicipal drain or pipe, channel or other conveyance, including natural and artificial (manmade) washes and ditches for conveying water, groundwater, drainage water or unpolluted water from any source, excluding sewage and industrial wastes, to waters of the State and United States.
Within the context of the Stormwater Management Manual, stormwater, whether one or two words, shall mean surface runoff resulting from precipitation.
means the permit issued by the CDPHE called the general permit for stormwater discharges associated with construction activities. Mesa County or the City of Grand Junction will also issue a stormwater construction permit for land disturbances related to new development.
Within the context of the Stormwater Management Manual, a stormwater management plan (SWMP) means the construction SWMP (CSWMP) and/or the post-construction SWMP.
means the area of the floodplain which carries the normal flow of the watercourse. (Mesa County Land Development Code Section 12.1).
means the area identified by the Colorado Department of Public Health and Environment based on the 2000 census and called the urban area of Mesa County. Within the context of the SWMM, urban area also includes the Redlands within the urban growth boundary of the County.
means the minimum storage volume, based on the eightieth percentile event, which is retained and released over a specified period of time, depending on the specific structural BMP and is based on the time it takes to fully drain the brim-full volume contained in storage.
means a structure designed to release the water quality capture volume over the specified period of time for the specific BMP.
means any groundwater, percolating or otherwise, lakes, bays, ponds, impounding reservoirs, springs, rivers, streams, creeks, estuaries, marshes, inlets, canals, wells, watercourses, drainage systems, and irrigation systems; all sources of water such as snow, ice, and glaciers; and all other bodies or accumulations of water, surface and underground, natural or artificial, navigable or nonnavigable, and including beds and banks of all watercourses and bodies of surface water, public or private, located wholly or partly within or bordering upon this State and within the jurisdiction of this State.
means the Grand Valley Stormwater Management Master Plan or other stormwater master plans approved by the Drainage Authority representing applicable municipalities and Mesa County.
means any area that is inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, under normal circumstances, a prevalence of vegetation typically adapted to the saturated soil conditions. Wetlands generally include swamps, marshes, bogs and similar areas.
(Res. 40-08 (§ 209), 3-19-08)