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HomeMy WebLinkAbout1.35 SWMP North Hangs 230215North Hangs Mine February 2023 1 North Hangs Mine Stormwater Management Plan In Conformance with the Guidelines set by: Colorado Department of Public Health and Environment Water Quality Control Division February 2023 Prepared for: Western Slope Materials, LLC. Represented by: North Hangs Mine February 2023 1 Table of Contents  Introduction ................................................................................................................................... 3 1. Key Elements of this Plan .................................................................................................. 3 Industrial Activity Description ........................................................................................................ 5 1. General .............................................................................................................................. 5 2. Standard Industrial Classification (SIC) Codes .................................................................. 8 3. Description of Operations ................................................................................................... 8 4. Basin Descriptions for Areas of Industrial Activity .............................................................. 9 5. Summary of Existing Discharge Sampling Data .............................................................. 12 6. Description of Sampling Points ........................................................................................ 13 7. Monitoring Procedures ..................................................................................................... 13 Stormwater Management Controls ............................................................................................. 14 1. SWMP Administrator ........................................................................................................ 14 2. Risk Identification and Assessment ................................................................................. 14 3. Preventative Maintenance ................................................................................................ 17 4. Good Housekeeping ........................................................................................................ 17 5. Stormwater Control Measures ......................................................................................... 17 6. Employee Training ........................................................................................................... 18 7. Testing for Non-stormwater Discharges ........................................................................... 18 8. Amendments .................................................................................................................... 18 Final Site Stabilization ................................................................................................................. 19 Comprehensive Inspection ......................................................................................................... 19 Record Keeping and Internal Reporting Procedure .................................................................... 19 Consistency with other Plans ...................................................................................................... 19 Allowable Non-stormwater Discharges ....................................................................................... 19 Appendix 1 Flow Measurements and Calculations ................................................................... 20 1. Stormwater Discharge ...................................................................................................... 20 2. Discharge Permit Sampling Requirements ...................................................................... 22 Appendix 2 - MSDS for All .......................................................................................................... 24 North Hangs Mine February 2023 2 Appendix 3 - Approved CDPHE Discharge Permit ..................................................................... 25 Appendix 4 - SWMP Map ............................................................................................................ 26 North Hangs Mine February 2023 1 STORMWATER MANAGEMENT PLAN (SWMP) Facility Name: North Hangs Mine Facility Type: Sand & Gravel Mining and Processing Date Initial Operations Started: 2022 (estimate) Facility Mailing Address: Western Slope Materials, LLC. PO Box 1319 Carbondale, Colorado 80138 970-963-2296 Facility Location Address: North Hangs Mine County Road 316 Silt, Colorado 81652 Stormwater Administrator Scott Mello Office: 970-963-2296 Cell: This plan was created using sound engineering practices by Ben Langenfeld of Lewicki and Associates on 2/15/2023. Lewicki and Associates is located at 3375 W Powers Circle, Littleton, CO 80123. Phone: (303) 346-5196. North Hangs Mine February 2023 2 Permittee Certifying Statement: I certify under penalty of law that this document and all attachments were prepared under my direction or supervision in accordance with a system designed to assure that qualified personnel properly gather and evaluate the information submitted. Based on my inquiry of the person or persons who manage the system, or those persons responsible for gathering the information, the information submitted is to the best of my knowledge and belief true, accurate and complete. I am aware that there are significant penalties for submitting false information, including the possibility of fine and imprisonment for knowing violations. Name: Scott Mello Company: Western Slope Materials LLC Title: General Manager Signature: ______________________________________ Date: __________________________________________ North Hangs Mine February 2023 3 Introduction This Stormwater Management Plan is prepared to mitigate potential impacts to Waters of the U.S. (Colorado River) resulting from the operations at the North Hangs Mine by Western Slope Materials, LLC. in Garfield County, Colorado. Water quality, drainage, monitoring, and pollution control are addressed in this Plan. Adherence to this plan will allow Western Slope Materials, LLC. to contain potential pollutants on the site and have a plan of action for minimizing the risk of contaminating surface waters. Discharge is to the Colorado River and the Bernudy Ditch and this certification is written for the standards of the Colorado River. This Plan includes stormwater and process water. The North Hangs Mine will be mined in two Phases. During the mining of each Phase, the active pits will serve as settling ponds, capturing stormwater and process water. All pits will have dewatering pumps and discharge pipes. 1. Key Elements of this Plan  Process Water (water used for periodic dewatering and runoff from gravel stockpiles) shall be contained within the site perimeter and routed to the settling ponds and mine pits on the site. Water is then pumped and discharged at the permitted discharge points for the site (See SWMP Map).  All disturbed areas will drain into the active pits or the be contained within the processing and stockpile area. See the SWMP Map for flow directions from particular portions of the site.  Stormwater from rainfall or snowmelt will inadvertently mix with process water or become process water if it flows across the disturbed area and shall be contained within the site and routed to the active pits or contained within the processing and stockpile area. These areas are a sufficient size to capture storm events and to allow solids to settle to the bottom. These areas will be monitored for sediment buildup and will be cleaned out as required to maintain settling volume.  Any discharge of Process Water to surface waters or to groundwater will be regulated through the Water Quality Control Division for discharges associated with sand and gravel production operations for stormwater and process water. Western Slope Materials, LLC. obtained a Discharge Permit to allow discharge of Process Water from the pit.  Any discharge of Process Water from the site shall be sampled and tested for flow, pH, Total Dissolved Solids, oil and grease (visual), Oil and Grease, Electrical Conductivity, North Hangs Mine February 2023 4 Total flow, and Total Suspended Solids. The person sampling discharge shall evaluate the flow rate and look for the presence of any oils (oily sheen).  The only acceptable methods of managing on site stormwater runoff are to contain it for Use in Operations, for Infiltration into the ground, for Evaporation into the air, or Discharge to the River.  Sediment is classified by the State as a potential pollutant that can negatively affect the quality of stormwater discharges. Loose sediment from gravel washing and trucks, etc. will be contained on site completely and not be allowed to be carried off site by stormwater. Erosion control methods such as revegetation or graveling of the processing and stockpile area will be implemented on the site to control sediment migration during stormwater runoff events.  The best method of managing site runoff water quality is to remove and properly dispose of any site contaminants that could be transported by stormwater runoff. All activities that could produce pollutants will be restricted to specific areas or have secondary containment. The designated area for this site is the plant and stockpile area. See the SWMP Map for the locations. Drips, leaks and spills will be cleaned up regularly. More detail on these items is provided later in this Plan.  All fuel tanks, petroleum product storage and other chemicals will be regulated under the SPCC plan for the site. North Hangs Mine February 2023 5 Industrial Activity Description 1. General Project Name and Location North Hangs Mine County Road 316 Silt, Colorado 81652 The North Hangs Mine is a sand and gravel operation located approximately one mile west southwest of Silt, CO located along the Colorado River just north of Interstate 70 at the terminus of Garfield County Road 316. The site, in relation to Silt, is shown on General Location Map. The site is located adjacent to the Colorado River, on the south side of the river, and encompasses 72.8 acres. The North Hangs Mine property is located in Section 9, Township 6 South, Range 92 West of the 6th P.M. North Hangs Mine February 2023 6 General Location Map North Hangs Mine February 2023 7 Owner Name and Address The North Hangs Mine is operated and owned by: Western Slope Materials, LLC. PO Box 1319 Carbondale, Colorado 80138 970-963-2296 Contact Person: Scott Mello Site Description The North Hangs Mine is a sand and gravel processing operation located approximately 1.0 mile southwest of the center of downtown Silt, CO at the terminus of Garfield County Road 316 as shown on the General Location Map. The site is bordered by the Colorado River to the north and east, I-70 to the south, and mixed rangeland to the west. The North Hangs Mine is 72.8 acres in size, all of which will be active. Processed gravel exits the site via trucks from Garfield County Road 316 road to the south. See the SWMP Map in Appendix D for more detail. The site is immediately south of the Colorado River. The water table is shallow, and the active pit floods when it is not being pumped. Mining will be conducted such that the active mining area will behave as the site sump for disturbance area runoff. The active pit will have a mine dewatering pump and discharge pipe which will discharge storm and process water to the Colorado River or the Bernudy Ditch. Once surface water is collected within the mining pits it will be collected in the pit floor perimeter ditches and be routed to the pit dewatering pumps. The pit dewatering pumps will then pump into existing drainage swales in undisturbed ground onsite to return to the Colorado River. Alternatively, pit dewatering will be discharged into the Bernudy Ditch. The pit pumps will always be located at least two feet below the active mining floor to ensure clean water pumping. All structures are shown on the SWMP Map. Stockpiles are located in the processing and stockpile portion of the site. The entire site is within the Federal Emergency Management Administration (FEMA) Floodplain Zone A (100-YR event). No floodway is mapped in this area, according to FEMA. Groundwater is roughly four feet below the natural grade and is the alluvial aquifer of the Colorado River. The 100-YR FEMA floodplain encompasses the entire mining area. All the disturbed area process water and storm runoff water is contained within the active pits or within the processing and stockpile area with the use of a stormwater berm. Sediment free water is pumped to the Colorado River or the Bernudy Ditch via outfalls. The SWMP Map shows the outfall locations. North Hangs Mine February 2023 8 2. Standard Industrial Classification (SIC) Codes SIC CODE INDUSTRY DESCRIPTION 1442 Processing of Sand & Gravel 3. Description of Operations Western Slope Materials, LLC. will conduct mining and gravel processing operations under a Division of Mining, Reclamation and Safety (DRMS) Permit. The DRMS permit will be released following full site reclamation. Western Slope Materials, LLC. is permitted for the following uses on the North Hangs Mine:  Dewatering from the pit during mining;  Crushing and stockpiling of aggregate;  Concrete production;  Truck loading and truck travel in and out of the site. Brief descriptions of these operations are provided below: Mining of the Pit All mining will require dewatering. Initial mining will consist of mine operations on the north and south sides of the Bernudy Ditch with the ditch still in its pre-mining condition. Once the Bernudy Ditch is rerouted, mining will take place in the ditch footprint. While the ditch is in place, it may be used for stormwater discharge via the pit pump. Once the ditch has been moved, the stormwater discharge outfall will be moved to the Colorado River. Dewatering of the Site Dewatering occurs with pumping and discharging occurring daily during mining activity. When mining is not occurring, the pit is allowed to flood. The site has a discharge permit through CDPHE to allow this discharge to the Colorado River. The permit number is COG___________. Process water is allowed to mix with the groundwater that is pumped from the mining area. The dewatering pump discharges via Outfall 001-A & Outfall 002-A, into the Colorado River and the Bernudy Ditch. Water test sampling occurs at the pump outlets. The permit allows for:  process water and comingled stormwater discharge;  pumped pit dewatering;  discharge of 4 million gallons of water per day North Hangs Mine February 2023 9 Sand and Gravel Processing Sand and gravel processing will consist of stockpiling gravels crushed to various specifications. A mobile crusher will be located in the processing and stockpile area and crushing of gravel will occur on site. See the SWMP map for locations. Fuel Storage A portable fuel tank will be set up in the mining area to supply equipment onsite. It will have full secondary containment. All equipment onsite will have onboard diesel tanks in full secondary containment. Full secondary containment has 110% of the volume of the tank that is in it. Chemical Storage No chemicals are stored onsite. Concrete production Concrete will be produced onsite for sale in the surrounding community. Shop activities There is no shop onsite. 4. Basin Descriptions for Areas of Industrial Activity Drainage Basins to Site Discharge Point One discharge point exists onsite for each active mining area. The entirety of the 72.8 acre site drains to the mining area. The discharge points are the destination for the majority of the site’s drainage area. The processing and stockpile area runoff will drain internally against the stormwater control berm that rings the processing area. Earthen berms of approximately 24” minimum height or greater are used as isolation berms that preclude stormwater in the disturbed area from running off site. No offsite areas drain to the site. Surface flow directions are shown on the SWMP Map. Drainage Basin to Colorado River As shown on the SWMP Plan Map, the entire disturbed area of the site will ultimately drain to the Colorado River or the Bernudy Ditch via the discharge points. This entire area is below isolation berms, containment ditches, or reclamation slopes. Off-site Sources There are none for this site. Uphill ground on the south sides of the site are precluded from entering the site via the topsoil berms. North Hangs Mine February 2023 10 On-site Stormwater and Process Water Runoff The disturbed areas of the site are handled as follows:  The majority of the disturbed area drains to the discharge points of the active mining area. The discharge points are preceded by pits for sediment trapping. Sediment is allowed to settle out in the pits prior to water being discharged.  Isolation berms of a minimum of 24 inches in height surround the site to contain and divert on site runoff to the pit.  The processing area runoff will drain internally against the stormwater control berm that rings the processing area. Stormwater that collects in the processing area will be allowed to infiltrate to the groundwater aquifer. The stormwater berm for the processing and stockpile area will be high enough to contain a 100-year precipitation event. A combined stormwater/process water discharge permit is in place for discharge from the mining pits. Stormwater volume was determined using the calculations below as described in the "Procedures for Determining Peak Flows in Colorado,” that includes and supplements Technical Release No. 55 "Urban Hydrology for Small Watersheds." Prior to discharge, sediment will be controlled by allowing for settling in the pit. North Hangs Mine February 2023 11 Stormwater Calculations Runoff Curve Numbers (CN) for Watershed Area Description Hydrologic Soil Group Area (acres) CN Disturbed Land Group A/D Soils 64.7 89 An area of 64.7 acres must be contained within the site disturbance to prevent sediment discharge. Group A/D soils are treated like Group A soils as the dual hydrologic soil group A/D represents the presence of a water table within 60 cm of the land surface, even though the saturated hydraulic conductivity may be favorable for water transmission. Hydrologic Soil Group Group A Soils: High infiltration (low runoff). Sand, loamy sand, or sandy loam. Infiltration rate > 0.3 inch/hr when wet. Group B Soils: Moderate infiltration (moderate runoff). Silt loam or loam. Infiltration rate 0.15 to 0.3 inch/hr when wet. Group C Soils: Low infiltration (moderate to high runoff). Sandy clay loam. Infiltration rate 0.05 to 0.15 inch/hr when wet. Group D Soils: Very low infiltration (high runoff). Clay loam, silty clay loam, sandy clay, silty clay, or clay. Infiltration rate 0 to 0.05 inch/hr when wet. The following areas were calculated using a scaled map image from 2016 in GIS software, which was used in the SWMP Map. North Hangs Mine February 2023 12 Runoff Curve Number and Runoff - End of Mining, Maximum Disturbance Scenario 1. Runoff curve number (CN) Cover Description CN Soil Type Area Disturbed ground 89 A/D 64.7 Acres CN (weighted): 89 2. Runoff Frequency 100 yr Rainfall, P (24-hour) 2.17 in Runoff Volume 4.7 Acre-Ft The available storage volume is: 398 acre-feet. Since the required storage volume of 14.9 acre feet is less than the available storage volume of 398 acre feet, there is more than enough storage volume to contain the storm event onsite. There is no threat of discharging if the reclaimed pit and active area sump fills up during a 100- year 24-hour storm event. Once it is deemed discharge will be in compliance, discharge via pump or gravity will take place. Groundwater Groundwater is dewatered from the active mining area via Outfall 001-A & Outfall 002-A. 5. Summary of Existing Discharge Sampling Data The North Hangs Mine discharges daily during mining due to dewatering of the pit. Records of sampling are kept on site and are available upon request by an inspector. The sample form is included in Appendix A. North Hangs Mine February 2023 13 6. Description of Sampling Points The North Hangs Mine has three discharge points for the site. These can be found on the SWMP Map. The discharge point is permitted with the Colorado Department of Public Health and Environment's (CDPHE) sand and gravel construction discharge permit. Parameters to be sampled are listed below in the following table. Effluent Parameter Measurement Frequency Sample Type Flow, MGD Monthly In-situ Total Flow Monthly Calculated Oil and Grease, visual Twice / Month Visual Oil and Grease, mg/l Contingent Grab pH, s.u. Twice / Month Grab Total Suspended Solids, mg/l Twice / Month Grab Total Dissolved Solids, mg/l Quarterly Grab Electrical Conductivity Quarterly Grab 7. Monitoring Procedures Samples will be collected in a manner that represents the discharge of all outfalls. Samples will be made with a clean, clear glass, or plastic container and examined in a well-lit area for: color, odor, clarity, floating solids, settled solids, suspended solids, foam, oil sheen, and other obvious indicators of pollution. Records of the results of sampling will be maintained with the SWMP located on site. All monitoring is conducted under the supervision of the SWMP Administrator. Yearly reports are sent to CDPHE-WQCD that detail the site’s progress in implementing strategies that will aid in meeting compliance with final selenium limitations. North Hangs Mine February 2023 14 Stormwater Management Controls 1. SWMP Administrator The SWMP Administrator is responsible for daily SWMP administration at the site. This designated person is listed at the beginning of this document along with their contact information. 2. Risk Identification and Assessment It is anticipated that no stormwater discharges will occur for any stormwater events prior to being allowed to settle in the pit. A summary of estimated risks if a discharge were to occur is presented below: Potential for Discharge from Basin: Pollutant Oil and Grease Low Total Dissolved Solids Low Total Suspended Solids Low pH (Outside Range 6.5 to 9.0) Low Identification of Potential Pollutant Sources Disturbed and Stored Soils All topsoil stockpiles will be maintained at an equal to or shallower than 2H:1V slope. To prevent erosion, all non-aggregate stockpiles will be seeded within 3 months of establishment. Herbicides are applied annually to control weed growth on all materials stockpiles. All stockpiled overburden and topsoil will ultimately be used in the reclamation process. Vehicle Tracking of Sediment As the site has considerable traffic of haul trucks entering and leaving the site on an ongoing basis, these activities have some potential to discharge sediment laden water but the BMP’s outlined in this Plan make a sediment laden discharge a remote possibility. The BMP most responsible for reduction of this potential is the fact that access roads within the site drain the sediment settling ponds and the processing and stockpile area, in addition to all access roads, will have a gravel floor. North Hangs Mine February 2023 15 Management of Contaminated Soils The site has no contaminated soils. If a spill occurs, any contaminated soils will be isolated from the area draining to the sediment settling ponds that have no discharge. These materials will be treated or hauled off site in conjunction with the procedures of the SPCC Plan. Loading and Unloading Operations Screened gravels are located on site in the stockpile area. All of these areas are contained by isolation berms and the settling pond, so the potential for significant pollution from these sources is very low. Outdoor Storage Activities (Storage of Chemicals) No chemicals are stored onsite. Vehicle and Equipment Maintenance and Fueling There is no used oil or chemical tanks on-site. Portable equipment will have contained fuel tanks with secondary containment. Minor maintenance will be performed on the portal equipment on an ‘as-needed’ basis. Without BMP’s there is a significant potential to discharge pollutant laden water but the BMP’s outlined in this Plan make pollutant laden discharges a remote possibility from this source. The primary BMP’s are a) the secondary containment of the tanks, b) containment of the areas on site where the fueling and maintenance occurs, and c) the inspection/training/maintenance procedures outlined in the SPCC Plan. Significant Dust or Particle Generating Processes Mining takes place in a 72.8 acre active area of the site. Without BMP’s there is a significant potential to discharge sediment laden water but the BMP’s outlines in this Plan make polluted laden discharges a remote possibility from this source. The primary BMP is as needed water spraying for road dust suppression. The inherently wet nature of the material at North Hangs should reduce the possibility of generating dust pollution. Additionally, the gravels at the North Hangs Mine contain few fines, thus limiting the possibility of pollution due to the liberation of these fines. Routine Maintenance Activities involving Fertilizers, Pesticides, Detergents, Fuels, Solvents, Oils, etc. No fuels, chemicals, fertilizers, etc. will be stored onsite. Limited routine maintenance activities on the portable plants will take place onsite. On site Waste Management Practices All onsite waste will be disposed in facilities operated by the local municipality. North Hangs Mine February 2023 16 Non-Industrial Waste Sources such as Worker Trash and Portable Toilets Portable toilets are used on site and are regularly serviced by a licensed contractor when workers are present. Worker trash is disposed of in the waste bins that are also taken to the approved landfill by the local waste management company. Without BMP’s there is a slight potential to discharge pollutant laden water but the BMP’s outlined in this Plan make pollutant laden discharges a remote possibility from this source. The primary BMP’s are the factory supplied waste trash bins, and porta potties, with the proper disposal of the trash and the porta potty waste. HMA Plants There are no HMA plants onsite. Concrete Batch Plant A portable batch plant will operate within the processing area. All cement additives will be stored within a designated area adjacent to the plant within secondary containment. Waste concrete will be recycled through the onsite plants. Concrete truck washout water will be contained in the processing area for evaporation and infiltration. Building Roofs There are no buildings onsite. Other Areas or Procedures Where Potential Spills Can Occur Other than the tanks identified in this Plan and the SPCC Plan, there are no other tanks or other sources that could result in a spill other than a rupture of hydraulic lines and diesel tanks associated with the mobile equipment on site, a loader and dozer. Without BMP’s there is a reasonable potential to discharge pollutant laden water but the BMP’s outlined in this Plan make polluted laden discharges a remote possibility from this source. The primary BMP’s are a) the fact that the quantities on the mobile equipment are small, less than 120 gallons of diesel fuel and 60 gallons of oil, and b) the SPCC Plan requires spill kits that will be used to mop up any spill with the mobile equipment. North Hangs Mine February 2023 17 3. Preventative Maintenance The following are the inspection and maintenance practices that will be implemented to control stormwater runoff quality:  The SWMP Administrator will be responsible for inspections, maintenance and oversight of any required repair operations. SWMP inspections will occur at least 2 times per year and records of these inspections will be kept on file on site with the SWMP Plan.  Ground slopes will be minimized to limit erosion and slow down flow during a stormwater event.  Final backfilled disturbed areas and stockpiles will be reseeded when practical to minimize erosion and sediment transport.  Inspect all tanks for leaks, proper dispensing equipment and adequate secondary containment in conjunction with the SPCC Plan.  Inspect all Isolation berms on site for disruption, erosion, or any other fault that requires maintenance. 4. Good Housekeeping The following good housekeeping practices will be employed at the site:  Substances stored on site will be stored in a neat, orderly manner in their appropriate containers.  Open containers of non-hazardous materials shall be covered to prevent mixing with stormwater.  The Safety Coordinator is responsible for day-to-day site operations and directing spill prevention, cleanup, and reporting. See North Hangs Mine SPCC Plan.  No waste oil will be stored onsite.  If drip pans are used, they will be cleaned on a regular basis and not allowed to fill with stormwater, and the contents disposed in a landfill approved to handle such waste.  No hazardous materials will be stored onsite. 5. Stormwater Control Measures This Stormwater Management Plan was developed to improve the water quality of stormwater runoff. The Stormwater Control Measures (SCMs) are intended to prevent the discharge of sediment laden stormwater from this site. North Hangs Mine February 2023 18 SCM Location Type Install. Date (Estimate) Implementation Specifics Sumps See SWMP Map Retention Pond/Active pits during mining 2026 Periodic clean out of accumulated sediment to maintain retention volume; Maintain positive drainage towards sump. Outfall 001‐A See SWMP Map Discharge point 2026 Pump based discharge with known flow rate. Outfall 002‐A See SWMP Map Discharge point 2026 Pump based discharge with known flow rate. Reclaimed Pit Lake See SWMP Map Groundwater lake 2035 Ensure positive drainage towards lake Isolation Berms See SWMP Map Berms/windrows 2026 Maintain height of at least 24 inches. Ensure vegetation on outslope. 6. Employee Training Western Slope Materials, LLC., through the Stormwater Administrator, will train and educate current and new employees on appropriate stormwater management, spill response, good housekeeping and materials storage practices. Best management practice training programs should also be conducted regarding improving the water quality of stormwater runoff. 7. Testing for Non-stormwater Discharges The only non-stormwater discharges expected at this site are stormwater and process water. Therefore, no testing for illicit connections or other non-stormwater discharges is proposed. 8. Amendments This SWMP plan must be amended whenever there is a change in facility design, construction, operation, or maintenance that materially affects Western Slope Materials, LLC. potential for discharge of pollutants (sediment, oils, etc.) into or upon waters of the United States. Such amendments must be implemented not later than six months after the change occurs. Any amendments to the SWMP plan will be developed by a Qualified Person. North Hangs Mine February 2023 19 Final Site Stabilization As required in the Colorado Division of Reclamation, Mining and Safety permit, the site is to be reclaimed to rangeland and groundwater ponds. Comprehensive Inspection The SWMP Administrator will conduct regular inspections of the site for stormwater management controls, spill control, maintenance, and cleanup. Inspections during at least the spring and fall of each year shall be conducted and the records of such inspections shall be maintained in files at the site together with the SWMP Plan. Inspections shall incorporate a complete review of all BMP’s outlined in this plan and will report on any BMP’s that are not functioning and/or require maintenance. Any discharges that are out of compliance with the discharge permit shall also be reported with corrective actions outlined. Record Keeping and Internal Reporting Procedure Incidents such as spills or other discharges, together with other relevant information describing the quality/quantity of stormwater, will be included in records maintained at the site. Inspection records and maintenance records will be maintained at the site. At least four comprehensive Stormwater Management Plan inspections (spring, summer, fall, and winter) will be conducted each year for annual reporting to CDPHE. These reports shall include the date of the inspection, findings and actions taken, and submitted with the Annual Stormwater Report due February 15 each year. Consistency with other Plans The SPCC Plan will be consistent with the SWMP Plan and will be available on site. A general discharge permit has been obtained from CDPHE. If other permits affecting stormwater are required of the site in the future, the SWMP will be modified to ensure consistency. These plans will also maintain consistency with the County and DRMS permits. Allowable Non-stormwater Discharges There is one process water and commingled storm water discharge point for this operation. That discharge is for dewatering of the pit and is covered under the Discharge Permit for the North Hangs Mine. The permit number is COG_______________. North Hangs Mine February 2023 20 Appendix 1 Flow Measurements and Calculations 1. Stormwater Discharge The site discharges from pumps at Outfall 001-A and Outfall 002-A. The pumps discharge water at a known rate. North Hangs Mine February 2023 21 The flow data measured on site using the procedures described above will be recorded on the form below. The completed forms are available on site with this SWMP Plan. Discharge Point Date of Measurement Discharge Flowrate (gpm) Person Taking Readings Comments Recording Form for Flow Measurements North Hangs Mine February 2023 22 2. Discharge Permit Sampling Requirements The North Hangs Mine will have multiple discharge points. These points are shown on the SWMP Map. These discharge points are permitted with CDPHE. The waterways surrounding the North Hangs Mine will also be inspected for visible sheen produced from oil or grease. Parameters to be sampled are listed below in the following table. Effluent Parameter Measurement Frequency Sample Type Limits Flow, MGD Continuous in-situ Calculated pH, s.u. Twice / Month Grab pH, s.u. 6.5-9 Total Suspended Solids, mg/l Twice / Month Grab Total Suspended Solids, mg/l 30 day average (30 mg/liter) 7 day average (45 mg/liter) Oil and Grease Twice / Month Visual Report Oil and Grease Twice / Month Grab 10 mg/L (contingent) Total Flow Monthly Grab Report Electrical Conductivity (EC) Quarterly Grab Report Total Dissolved Solids, mg/l Quarterly Grab Total Dissolved Solids, mg/l – Report amount only North Hangs Mine February 2023 23 Visual Sampling Record Sheet Sample Location Collection Date/Time Assessment Date/Time Sampler (print & sign) Visual Assessor (print & sign) Nature of Discharge Discharge Observations Source of Any Observed Contamination Was the Sample Taken Within 30 Minutes of Discharge? If, NO, why not? North Hangs Mine February 2023 24 Appendix 2 - MSDS for All North Hangs Mine February 2023 25 Appendix 3 - Approved CDPHE Discharge Permit North Hangs Mine February 2023 26 Appendix 4 - SWMP Map Please see the CDRMS Maps C-2 and C-3.