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EROSION AND SEDIMENTATION CONTROL
§ 11.05.060.010 PURPOSE.
   (A)   The objective of the erosion and sediment control standards is to minimize erosion of disturbed areas during the construction of a project. Erosion and subsequent sediment transport can have a significant impact on the water quality of receiving surface waters. Sediment loads to surface waters increase turbidity, increase water temperatures, degrade fish habitat and spawning areas, and depress dissolved oxygen concentrations. Moreover, toxic substances, trace metals and nutrients which are absorbed to soil particles can be transported into surface waters as well. The addition of these substances to surface waters degrades the existing water quality.
   (B)   No run-off containing sediment shall be permitted to flow off of any construction site. Sediment shall not be discharged into storm drainage systems, waterways or wetlands. The contractor shall provide and maintain the required sediment control barriers. The control barriers shall not be removed until all roadways have been paved and a permanent and stable vegetation cover has been established.
   (C)   BMPs for erosion and sediment control are selected to meet the BMP objectives based on specific site conditions, construction activities and cost effectiveness. Since construction site conditions are constantly changing, different BMPs may be needed at different times during construction.
   (D)   In most cases, permanent BMPs can be implemented most effectively when they can be integrated into other aspects of the project design. This requires that stormwater control be considered early in the design process. Some BMPs can be incorporated into stormwater detention facilities with modest design refinements and limited increases in land area and cost.
(Prior Code, § 11.05.060.010) (Ord. 2019-9, passed 9-3-2019; Ord. 2021-15, passed 12-20-2021)
§ 11.05.060.020 MINIMUM CRITERIA FOR AN EROSION CONTROL PLAN.
   An ESCP is required for land-disturbing activities which include, but are not limited to, excavation, planting, tilling and grading, which disturbs the natural or improved vegetative ground cover so as to expose soil to the erosive forces of rain, stormwater run-off or wind. Any activity where the area disturbed exceeds 5,000 square feet; provided it does not obstruct a watercourse and is not located in a floodplain.
(Prior Code, § 11.05.060.020) (Ord. 2019-9, passed 9-3-2019; Ord. 2021-15, passed 12-20-2021)
§ 11.05.060.030 EROSION AND SEDIMENT CONTROL PLAN (ESCP).
   (A)   A professional with a good working knowledge of hydrology and ESCP practices, must prepare the ESCP. A copy of the ESCP must be located on the construction site or within reasonable access to the site. As site construction progresses, the ESC plan may require modification to reflect changes in site conditions.
   (B)   In general, the ESCP will consist of a narrative and a drawing. The project designer may choose to have the narrative included on a drawing or issued as a report. The Montana Department of Transportation is a good source for erosion control details (the Montana Department of Transportation Erosion and Sediment Control Best Management Practices Manual). The ESCP must contain sufficient information to demonstrate to the PWD that potential problems associated with erosion, sediment and pollution have been adequately addressed for the proposed project. The drawings and notes should be clear and concise and describe when and where each BMP is to be implemented and details as necessary.
(Prior Code, § 11.05.060.030) (Ord. 2019-9, passed 9-3-2019; Ord. 2021-15, passed 12-20-2021)
§ 11.05.060.040 BEST MANAGEMENT PRACTICES FOR AN ESCP.
   At a minimum, the following items shall be addressed in the ESCP.
   (A)   Construction sequence.
      (1)   Install temporary BMPs; constructing sediment trapping BMPs as one of the first steps prior to grading;
      (2)   Stabilize roadway approaches and temporary access points with the appropriate construction entry BMP;
      (3)   Protect all permanent stormwater facilities utilizing the appropriate BMPs;
      (4)   Install permanent ESC controls, when applicable; and
      (5)   Remove temporary ESC controls when:
         (a)   Permanent ESC controls, when applicable, have been completely installed;
         (b)   All land-disturbing activities that have the potential to cause erosion or sedimentation problems have ceased; and
         (c)   Vegetation had been established in the areas noted as requiring vegetation on the accepted ESC plan on file with the City PWD.
   (B)   Construction access route.
      (1)   Limit access for construction vehicles to one route whenever possible;
      (2)   Stabilize the construction access routes to minimize the tracking of sediment onto roadways;
      (3)   Install temporary vehicle tracking approach at site entrance locations;
      (4)   Inspect all roadways, at the end of each day, adjacent to the construction access route. If it is evident that sediment has been tracked off-site and/or beyond the roadway approach, removal and cleaning is required;
      (5)   If sediment removal is necessary prior to street washing, it shall be removed by shoveling or sweeping and transported to a controlled sediment disposal area; and
      (6)   If street washing is required to clean sediment tracked off-site, once sediment has been removed, street wash wastewater shall be controlled by pumping back on-site or otherwise prevented from discharging into systems tributary to waters of the state; and, locate wheel washes or tire baths, if applicable to ESCP, on site. Dispose of wastewater into a separate temporary on-site treatment facility in a location other than where a permanent stormwater facility is proposed.
   (C)   Protection of inlets.
      (1)   Protect inlets, drywells, catch basins and other stormwater management facilities from sediment, whether or not facilities are operable, so that stormwater run-off does not enter the conveyance system (both on- and off-site) without being treated or filtered to remove sediment; and
      (2)   Keep roads adjacent to inlets clean; sediment and street wash water shall not be allowed to enter the conveyance system (both on- and off-site) without prior treatment.
   (D)   Run-off from construction sites.
      (1)   Protect down-gradient properties, waterways and stormwater facilities from possible impacts due to increased flow rates, volumes and velocities of stormwater run-off from the project site that may temporarily occur during construction;
      (2)   Run-off from the construction site through the detention/retention storage pond or swales shall be addressed in the construction sequence. No sediment laden water shall pass through the flow control system and discharge to an off-site storm conveyance system;
      (3)   Construct stormwater control facilities (detention/retention storage pond or swales) before grading begins. These facilities shall be operational before the construction of impervious site improvements; and
      (4)   Protect permanent infiltration facilities that are used for flow control during construction.
   (E)   Washout site for concrete trucks and equipment. Designate the location of a slurry pit where concrete trucks and equipment can be washed out. Slurry pits are not to be located in or upstream of a swale, drainage area, stormwater facility or water body, or in an area where a stormwater facility is existing or proposed.
   (F)   Material storage/stockpile.
      (1)   Identify locations for storage/stockpile areas, within the proposed ESCP boundaries, for any soil, earthen and landscape material that is used or will be used on-site;
      (2)   Stockpile materials (such as, topsoil) on-site, keeping off roadway and sidewalks; and
      (3)   Maintain on-site, as feasible, items such as gravel and a roll of plastic, for emergency soil stabilization during a heavy rain event, or for emergency berm construction.
   (G)   Permanent BMPs.
      (1)   Include permanent BMPs, if necessary, in the ESCP to ensure the successful transition from temporary BMPs to permanent BMPs; and
      (2)   Restore and rehabilitate temporary BMPs that are proposed to remain in place after construction as permanent BMPs.
   (H)   Maintenance of BMPs.
      (1)   Inspect on a regular basis (at a minimum, bi-weekly and daily during/after a run-off producing storm event) and maintain all ESC BMPs to ensure successful performance of the BMPs. Conduct maintenance and repair in accordance with individual ESC BMPs outlined in this section; and
      (2)   Remove temporary ESC BMPs within 30 days after they are no longer needed. Permanently stabilize areas that are disturbed during the removal process.
(Prior Code, § 11.05.060.040) (Ord. 2019-9, passed 9-3-2019; Ord. 2021-15, passed 12-20-2021)
§ 11.05.060.050 STORMWATER POLLUTION PREVENTION PLAN.
   Construction sites or activities disturbing one acre or more, or when stormwater discharge to state waters can occur, the MDEQ requirements for the general permit for stormwater discharges associated with construction activity apply. Requirement associated with the general permit and SWPPP can be found on DEQ’s website.
(Prior Code, § 11.05.060.050) (Ord. 2019-9, passed 9-3-2019; Ord. 2021-15, passed 12-20-2021)
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