1173.08 PERFORMANCE STANDARDS.
The Storm Water Pollution Prevention Plan must contain a description of the controls appropriate for each construction operation and the applicant must implement such controls. The Storm Water Pollution Prevention Plan must clearly describe for each major construction activity the appropriate control measures; the general sequence during the construction process under which the measures will be implemented; and the contractor responsible for implementation (e.g., contractor A will clear land and install perimeter controls and contractor B will maintain perimeter controls until final stabilization). The SWP3 shall identify all subcontractors engaged in activities that impact storm water runoff. The SWP3 shall contain signatures from all of the identified subcontractors indicating that they have been informed and understand their roles and responsibilities in complying with the SWP3.
The controls shall include the following minimum components:
(a) Non-structural Preservation Measures: The Storm Water Pollution Prevention Plan must make use of practices that preserve the existing natural condition to the maximum extent practicable. Such practices may include preserving riparian areas, preserving existing vegetation and vegetative buffer strips, phasing of construction operations in order to minimize the amount of disturbed land at any one time, and designation of tree preservation areas or other protective clearing or grubbing practices.
(b) Erosion Control Practices: The Storm Water Pollution Prevention Plan must make use of erosion controls that are capable of providing cover over disturbed soils. A description of control practices designed to restabilize disturbed areas after grading or construction shall be included in the Storm Water Pollution Prevention Plan. The Storm Water Pollution Prevention Plan must provide specifications for stabilization of all disturbed areas of the site and provide guidance as to which method of stabilization will be employed for any time of the year. Such practices may include: temporary seeding, permanent seeding, mulching, matting, sod stabilization, vegetative buffer strips, phasing of construction operations, the use of construction entrances, and the use of alternative ground cover.
Erosion control practices must meet the following requirements:
(1) Stabilization. Disturbed areas must be stabilized as specified in Tables 1 and 2 below.
Table 1: Permanent Stabilization
Area requiring permanent stabilization | Time Frame to apply erosion control |
Any area that will lie dormant for one year or more. | Within 7 days of the most recent disturbance. |
Any area within 50 feet of a stream and at a final grade | Within 2 days of reaching final grade. |
Any area at final grade | Within 7 days of reaching final grade within that area. |
Table 2: Temporary Stabilization
Area requiring temporary stabilization | Time Frame to apply erosion controls |
Any disturbed area within 50 feet of a stream and not at final grade | Within 2 days of the most recent disturbance if that area will remain idle for more than 21 days. |
For all construction activities, any disturbed area, including soil stockpiles that will be dormant for more than 21 days but less than one year, and not within 50 feet of a stream. | Within 7 days of the most recent disturbance with the area. |
Disturbed areas that will be idle over winter. | Prior to November 1. |
Note: Where vegetative stabilization techniques may cause structural instability or are otherwise unobtainable, alternative stabilization techniques must be employed. These techniques may include mulching or erosion matting. | |
(2) Permanent stabilization of conveyance channels. Applicants shall undertake special measures to stabilize channels and outfalls and prevent erosive flows. Measures may include seeding, dormant seeding, mulching, erosion control matting, sodding, riprap, natural channel design with bioengineering techniques, or rock check dams, all as defined in the most recent edition of Rainwater and Land Development or the Field Office Technical Guide presently available at www.nrcs.usda.gov/technical/efotg/
(c) Runoff Control Practices: The Storm Water Pollution Prevention Plan shall incorporate measures that control the flow of runoff from disturbed areas so as to prevent erosion. Such practices may include rock check dams, pipe slope drains, diversions to direct flow away from exposed soils and protective grading practices. These practices shall divert runoff away from disturbed areas and steep slopes where practicable.
(d) Sediment Control Practices: The Storm Water Pollution Prevention Plan shall include a description of, and detailed drawings for, all structural practices that shall store runoff, allowing sediments to settle and/or divert flows away from exposed soils or otherwise limit runoff from exposed areas. Structural practices shall be used to control erosion and trap sediment from a site remaining disturbed for more than 14 days. Such practices may include, among others: sediment settling ponds, silt fences, storm drain inlet protection, and earth diversion dikes or channels which direct runoff to a sediment settling pond. All sediment control practices must be capable of ponding runoff in order to be considered functional. Earth diversion dikes or channels alone are not considered a sediment control practice unless used in conjunction with a sediment settling pond.
Sediment control practices must meet the following requirements:
(1) Timing. Sediment control structures shall be functional throughout the course of earth disturbing activity. Sediment basins and perimeter sediment barriers shall be implemented prior to grading and within seven (7) days from the start of grubbing. They shall continue to function until the up slope development area is restabilized. As construction progresses and the topography is altered, appropriate controls must be constructed or existing controls altered to address the changing drainage patterns.
(2) Sediment settling ponds: A sediment settling pond, or equivalent best management practice upon approval from the City of Aurora Engineer, is required for any one of the following conditions, as determined in Table 3 below:
A. Concentrated storm water runoff.
B. Runoff from drainage areas that exceeds the design capacity if silt fence, other sediment barriers, or inlet protection.
C. 10-acres of disturbed drainage.
The sediment settling pond shall provide both a sediment storage zone and a dewatering zone. The volume of the dewatering zone shall be at least 67 cubic yards of storage per acre of total contributing drainage area and have a minimum of 48-hour drain time for sediment basins serving a drainage area over 5 acres.
The volume of the sediment storage zone shall be calculated by one of the following methods:
A. The volume of the sediment storage zone shall be 1,000 ft3 per disturbed acre within the watershed of the basin.
B. The volume of the sediment storage zone shall be the volume necessary to store the sediment as calculated with a generally accepted erosion prediction model.
When determining the total contributing drainage area, off-site areas and areas which remain undisturbed by construction activity must be included unless runoff from these areas is diverted away from the sediment settling pond and is not co-mingled with sediment-laden runoff. The depth of the dewatering zone must be less than or equal to five (5) feet. The configuration between the inlets and the outlet of the basin must provide at least two units of length for each one unit of width (>2:1 length: width ratio), however a length to width ratio of 4:1 is recommended. Sediment must be removed from the sediment-settling pond when the design capacity has been reduced by 40 percent. This limit is typically reached when sediment occupies one-half of the basin depth. When designing sediment settling ponds, the applicant must consider public safety, especially as it related to children, as a design factor for the sediment basin and alternative sediment controls must be used where site limitations would preclude a safe design. The use of a combination of sediment and erosion control measures in order to achieve maximum pollutant removal is encouraged.
(3) Silt fence and diversions. Sheet flow runoff from denuded areas shall be intercepted by silt fence or diversions to protect adjacent properties, water resources, and wetlands from sediment transported via sheet flow. Where intended to provide sediment control, silt fence shall be placed on a level contour and shall be capable of temporarily ponding runoff. The relationship between the maximum drainage area to silt fence for a particular slope range is shown in Table 3 below. Storm water diversion practices shall be used to keep runoff away from disturbed areas and steep slopes. Such devices, which include swales, dikes or berms, may receive storm water runoff from areas up to 10 acres. Placing silt fence in parallel does not extend the permissible drainage area which is served by the silt fence.
Table 3: Maximum Drainage Area to Silt Fence
Maximum Drainage Area (acres ) to 100 linear feet of silt fence | Range of Slope for a drainage area (%) |
0.5 | <2% |
0.25 | >2%but <20% |
0.125 | >20% but <50% |
(4) Inlet protection. Erosion and sediment control practices, such as boxed inlet protection, shall be installed to minimize sediment-laden water entering active storm drain systems. All inlets receiving runoff from drainage areas of one or more acres will require a sediment settling pond. Straw or hay bales are not acceptable forms of inlet protection.
(5) Off-site tracking of sediment and dust control. Best management practices must be implemented to ensure sediment is not tracked off-site and that dust is controlled. These best management practices must include, but are not limited to, the following:
A. Construction entrances shall be built and shall serve as the only permitted points of ingress and egress to the development area. These entrances shall be built of a stabilized pad of aggregate stone or recycled concrete or cement sized greater than ½" in diameter, placed over a geotextile fabric, and constructed in conformance with specifications in the most recent edition of the Rainwater and Land Development Manual
B. Streets directly adjacent to construction entrances and receiving traffic from the development area shall be cleaned daily to remove sediment tracked off-site. If applicable, the catch basins on these streets nearest to the construction entrances shall also be cleaned weekly.
C. Silt fence or construction fence installed around the perimeter of the development area to ensure that all vehicle traffic adheres to designated construction entrances.
D. Designated wheel-washing areas. Wash water from these areas must be directed to a designated sediment trap, the sediment-settling pond, or to a sump pump for dewatering in conformance with Section 1173.08
(g).
E. The washing of concrete material into a street, catch basin, or other public facility or natural resource is prohibited. A designated area for concrete washout shall be made available.
F. Applicants shall take all necessary measures to comply with applicable regulations regarding fugitive dust emissions, including obtaining necessary permits for such emissions. The City of Aurora Engineer may require dust controls including the use of water trucks to wet disturbed areas, tarping stockpiles, temporary stabilization of disturbed areas, and regulation of the speed of vehicles on the site.
(6) Surface Waters of the State Protection. Construction vehicles shall avoid water resources and wetlands. If the applicant is permitted to disturb areas within 50 feet of a water resource or wetland, the following conditions shall be addressed in the Storm Water Pollution Prevention Plan:
A. All best management practices and stream crossings shall be designed as specified in the most recent edition of the Rainwater and Land Development Manual
B. Structural practices shall be designated and implemented on site to protect water resources or wetlands from the impacts of sediment runoff.
C. No structural sediment controls (e.g., the installation of silt fence or sediment settling pond in-stream) shall be used in a water resource or wetland.
D. Where stream crossings for roads or utilities are necessary and permitted, the project shall be designed such that the number of stream crossings and the width of the disturbance are minimized.
E. Temporary stream crossings shall be constructed if water resources or wetlands will be crossed by construction vehicles during construction. These temporary stream crossings must also minimize disturbance to the stream.
F. Construction of bridges, culverts, or sediment control structures shall not place soil, debris, or other particulate material into or close to the water resources or wetlands in such a manner that it may slough, slip, or erode.
(7) Modifying controls. If periodic inspections or other information indicates a control has been used inappropriately or incorrectly, the applicant shall replace or modify the control for site conditions.
(e) Non-sediment Pollutant Controls. No solid or liquid waste, including building materials, shall be discharged in storm water runoff The applicant must implement site best management practices to prevent toxic materials, hazardous materials, or other debris from entering water resources or wetlands. These practices shall include but are not limited to the following:
(1) Waste Materials: A covered Dumpster shall be made available for the proper disposal of garbage, plaster, drywall, grout, gypsum, and other waste materials.
(2) Concrete Truck Wash Out: The washing of concrete material into a street, catch basin, or other public facility or natural resource is prohibited. A designated area for concrete washout shall be made available.
(3) Fuel/Liquid Tank Storage: All fuel / liquid tanks and drums shall be stored in a marked storage area. A dike shall be constructed around this storage area with a minimum capacity equal to 110% of the volume of all containers in the storage area.
(4) Toxic or Hazardous Waste Disposal: Any toxic or hazardous waste shall be disposed of properly.
(5) Contaminated Soils Disposal and Runoff: Contaminated soils from redevelopment sites shall be disposed of properly. Runoff from contaminated soils shall not be discharged from the site. Proper permits shall be obtained for development projects on solid waste landfill sites or redevelopment sites.
(f) Compliance with Other Requirements. The Storm Water Pollution Prevention Plan shall be consistent with applicable State and/or local waste disposal, sanitary sewer, or septic system regulations, including provisions prohibiting waste disposal by open burning, and shall provide for the proper disposal of contaminated soils located within the development area.
(g) Trench and Ground Water Control. There shall be no sediment-laden or turbid discharges to water resources or wetlands resulting from dewatering activities. If trench or ground water contains sediment, it must pass through a sediment-settling pond or other equally effective sediment control device, prior to being discharged from the construction site. Alternatively, sediment may be removed by settling in place or by dewatering into a sump pit, filter bag or comparable practice. Ground water dewatering which does not contain sediment or other pollutants is not required to be treated prior to discharge. However, care must be taken when discharging ground water to ensure that it does not become pollutant-laden by traversing over disturbed soils or other pollutant sources.
(h) Internal Inspections. All controls on the site shall be inspected at least once every seven calendar days and within 24 hours after any storm event greater than one-half inch of rain per 24 hour period.
The applicant shall assign qualified inspection personnel to conduct these inspections to ensure that the control practices are functional and to evaluate whether the Storm Water Pollution Protection Plan (SWP3) is adequate, or whether additional control measures are required. Qualified inspection personnel are individuals which are Certified Erosion, Sediment, and Storm Water Inspector (CESSWI), a Professional Engineer, or a Certified Professional in Erosion and Sediment Control (CPESC).
The Qualified Inspection Personnel shall certify, in writing, to a City of Aurora Engineer or his designee, compliance with the following:
(1) Disturbed areas and areas used for storage of materials that are exposed to precipitation shall be inspected for evidence of or the potential for, pollutants entering the drainage system.
(2) Discharge locations shall be inspected to determine whether erosion and sediment control measures are effective in preventing significant impacts to the receiving water resource or wetland.
(3) Locations where vehicles enter or exit the site shall be inspected for evidence of off-site vehicle tracking.
(4) Corrective action required setting forth any and all changes to the SWP3 and/or implementation dates.
(5) Erosion and sediment control measures identified in the SWP3 shall be observed to ensure that they are operating correctly. The applicant shall utilize an inspection form provided by the City of Aurora or an alternate form acceptable to the City of Aurora Engineer. The inspection form shall include:
A. The inspection date;
B. Names, titles and qualifications of personnel making the inspections;
C. Weather information for the period since the last inspection, including a best estimate of the beginning of each storm event, duration of each storm event and approximate amount of rainfall for each storm event in inches, and whether any discharges occurred;
D. Weather information and a description of any discharges occurring at the time of inspection; and,
E. Locations of:
1. Discharges of sediment or other pollutants from the site;
2. BMPs that need to be maintained;
3. BMPs that failed to operate as designed or proved inadequate for a particular location; and.
4. Whether additional BMPs are needed that did not exist at the time of inspection.
(6) The applicant shall maintain for three (3) years following the submittal of a notice of termination form, the results of these inspection, the names and qualifications of personnel making the inspection, the dates of inspections, major observations relating to the implementation of the SWP3, a certification as to whether the facility is in compliance with the SWP3, and information on any incidents of non-compliance determined by these inspections.
(i) Maintenance. The Storm Water Pollution Prevention Plan shall be designed to minimize maintenance requirements. All control practices shall be maintained and repaired as needed to ensure continued performance of their intended function until final stabilization. All sediment control practices must be maintained in a functional condition until all up slope areas they control reach final stabilization. The applicant shall provide a description of maintenance procedures needed to ensure the continued performance of control practices and shall ensure a responsible party and adequate funding to conduct this maintenance, all as approved by the City of Aurora Engineer.
When inspections reveal the need for repair, replacement, or installation of erosion and sediment control best management practices, the following procedures shall be followed:
(1) When practices require repair or maintenance. If an internal inspection reveals that a control practice is in need of repair or maintenance, with the exception of a sediment-settling pond, it must be repaired or maintained within three (3) days of the inspection. Sediment settling ponds must be repaired or maintained within ten (10) days of the inspection.
(2) When practices fail to provide their intended function. If an internal inspection reveals that a control practice fails to perform its intended function as detailed in the Storm Water Pollution Prevention Plan and that another, more appropriate control practice is required, the Storm Water Pollution Prevention Plan must be amended and the new control practice must be installed within ten (10) days of the inspection.
(3) When practices depicted on the Storm Water Pollution Prevention Plan are not installed. If an internal inspection reveals that a control practice has not been implemented in accordance with the schedule, the control practice must be implemented within ten (10) days from the date of the inspection. If the internal inspection reveals that the planned control practice is not needed, the record must contain a statement of explanation as to why the control practice is not needed.
(j) Final Stabilization. Final stabilization shall be determined by the City of Aurora Engineer. (Ord. 2010-182. Passed 2-14-11.)