3 BackgroundIn 1992, the State of Colorado stormwater regulation went into effect to control municipal and industrial stormwater discharges, based on EPA regulations.The State regulation(5 CCR ) covers discharges from specific types of industries including construction sites, and storm sewer systems for certain municipalities. In Colorado, the program is under the Colorado Department of Public Health &Environment.The Colorado program is referred to as the Colorado Discharge Permit System (CDPS), and regulated stormwater discharges from construction activities are covered under the CDPS General Permit for Stormwater Discharges Associated with Construction Activities (the Stormwater Construction Permit)
4 BackgroundJune 30, 2005 – The Colorado Water Quality Control Division extends permitting for stormwater discharges from construction activities associated with small construction activity (those that disturb between one and five acres)Stormwater permitting was previously required for all sites with disturbance in excess of five acres
5 Colorado Regulatory Requirements Stormwater Discharges are Regulated by the CDPHE Water Quality Control DivisionStormwater permit coverage is required for all construction activities that disturb one acre or greaterCoverage is also required for construction that is part of a larger common plan of developmentOil & gas activities covered include construction of well pads, road, pipelines, pumping stations, etc.
6 Colorado Regulatory Requirements (cont.) Permit coverage for construction activities is obtained under CDPHE’s Construction General PermitApplication for coverage must be submitted at least 10 days prior to the start of constructionA Stormwater Management Plan (SWMP) has to be prepared at the time the application is submittedImplementation of SWMP must occur immediately upon initiation of construction
7 Colorado Regulatory Requirements (cont.) CDPHE Permit Requires Routine Self-InspectionsActive Sites (Disturbed but Not Seeded)Must be inspected at least once every 14 days and after any precipitation or snowfall event that causes erosionCompleted Sites (Seeded but not Stabilized)Must be inspected at least once every monthStabilized Sites (at least 70% vegetation established)Inspections no longer requiredInspections are not required when snow cover exists over the entire site for an extended period and melting conditions do not existInspection records must be maintained for a period of 3 years and must be made available to CDPHE/EPA upon request
8 Colorado Regulatory Requirements (cont.) CDPHE Allows Some Flexibility in Defining the Area to be Covered by a Stormwater PermitSingle site with disturbance greater than 1 acreMultiple sites within a common plan of developmentInterpreted to be sites up to ¼ mile apart and/or having the area between the sites disturbed
9 Colorado Regulatory Requirements (cont.) Final Stabilization as Applied to ConstructionConstruction has been completed and disturbed areas have been built on, paved, or at least 70% of pre-disturbance vegetation has been established or equivalent permanent, physical erosion reduction methods have been employedStabilized unpaved surfaces – Dirt road surfaces and portions of pads that cannot be revegetated due to operational necessity are considered finally stabilized as long as they are prepared as to prevent ongoing erosion issues
10 Stormwater Management Plans (SWMPs) SWMP Goalto describe appropriate controls and measures to improve water quality by reducing pollutants in stormwater discharges and ensure compliance with the requirements of the stormwater permit. The SWMP must be completed and implemented at the time the project breaks ground, and revised if necessary as construction proceeds to accurately reflect the conditions and practices at the site.
11 Stormwater Management Plans (Cont.) SWMP RequirementsGeneral RequirementsPrepared in accordance with good engineering, hydrologic and pollution control practicesIdentifies Best Management Practices (BMPs)Identifies potential sources of pollution associated with construction activityConstruction operations must implement the provisions of the SWMP
12 Stormwater Management Plans (Cont.) SWMP Requirements (cont.)Narrative Site DescriptionDescribe construction activitySequence for major activitiesEstimates of total area of site and area that will be disturbedEstimate of runoff coefficient of the site before and after constructionLocation of other potential pollution sourcesLocation and description of non-stormwater components of discharge (springs, landscape irrigation return, etc.)Name and description of receiving water(s) or municipal storm sewer
13 Stormwater Management Plans (Cont.) SWMP Requirements (cont.)Site MapConstruction site boundariesAreas of soil disturbanceAreas of cut and fillAreas used for storage of building materials, soils or wastesLocation of any dedicated batch plantsLocation of major erosion control facilities or structuresSurface watersBoundaries of 100-year flood plains
14 Stormwater Management Plans (Cont.) SWMP Requirements (cont.)BMPs and Other ControlsDescription of appropriate controls and measures that will be implementedStructural PracticesNon-Structural PracticesIdentify procedures to control spills, etc. (coordinate with SPCC plans)Identify other measures to control pollutants (waste disposal, limiting off-site soil tracking, etc.)Site stabilization methodsInspection and maintenance procedures
15 Stormwater Management Plans (Cont.) SWMP Requirements (cont.)SWMP RevisionThe SWMP must be modified to accurately reflect the actual field conditions and BMPs usedSWMP AdministrationThe SWMP must be on site during active construction and site inspections and available to those directly responsible for installing an maintaining BMPs
16 Best Management Practices (BMPs) Reflect the measures taken to control stormwater as dictated by the SWMP.Proper selection and implementation of BMPs are the keys to an effective stormwater management programCommon sense approachThere is no one right answerOften involves trial and error to find what works bestDescribe a wide range of structural treatment processes, pollution prevention practices, schedules of activities, prohibition on practices, and other management practices
17 Best Management Practices (cont.) BMPs fall into 2 general categoriesNonstructural – Operational/managerial techniques, such asPhasing of operationsHousekeeping practicesSpill preventionPreventive maintenancePreserving natural vegetationStructural – Physical processesErosion Control BMPs – Practices to prevent the erosion of soilSediment Control BMPs – Practices to remove sediment from runoff
19 Silt Fence The silt fence has been installed correctly The silt fence needs to be repaired and BMPs should not be placed in drainage waters of the US
20 Straw Bales/WaddlesThis technique utilizes bound straw bales to filter sediment from runoff of small areasLimitationsFilters sheet flow from small drainage areasShort term useDecomposes and/or consumed by livestockRemoval of stakes will be necessary after stabilization is completeInstallationEmbed into trenchAnchor with 2 stakes (metal or wood)Compact backfill on the upgradient sideUse at outfall points from sediment ponds, diversion ditches, turnouts, etc.
22 Sediment Pond (Trap)This technique uses a pond to hold sediment-laden water so that sediment can settle and water is absorbed into the soil. Sediment traps are useful for construction sites where excessive runoff will need to be captured and filtered.LimitationsSize of surrounding areaRequire regular maintenance due to sediment build-upInstallationExcavate trap or basin within area where runoff may be directed towardSideslopes should be machine compactedSideslopes should be 2:1 or flatterVolume of trap should handle runoff from 2-year storm eventConstruct spillway or outfall structure with rock, straw bale, or other appropriate BMP
23 Sediment PondVertical and steep slopes should be avoided as these will result in erosion
24 Diversion DitchThis technique is useful to filter sediment from concentrated flows and/or runoff of moderate grades and larger drainage areas. Additionally, rock berms may be utilized to reduce velocity of flows within diversion ditchesLimitationsAvailability and/or cost of rockDifficult to remove after constructionRequire regular maintenance due to sediment build-uInstallationUse medium to large diameter rockMay secure rock within woven wire sheathing (not required)Berm side slopes should be 3:1 or flatterTop of berm should be a minimum of 2 feet wide
26 Geotextiles/Erosion Blankets Geotextiles and erosion blankets are typically a porous fabric constructed of woven fibers. They are useful for stabilization and preventing erosion on slopes, especially adjacent to streamsLimitationsDecomposeEffectiveness depends on proper installationExpensiveInstallationSelect appropriate fabric type for necessary purposeRemove any protruding rocks and smooth soil prior to installationFabric needs to be entrenched into the soilAnchor fabric securelyApply seed prior to fabric installation for final stabilization of sitesFollow manufacturer’s recommendations for installation
28 Surface Roughening (Tracking) This technique utilizes the horizontal grooves created by tracks of construction equipment to reduce runoff flow velocities. Tracks are established on the slopes perpendicular to water flow.LimitationsNot for use on rocky slopesMay cause soil compaction which limits vegetation re-growthRoughening may have to be re-established if lost due to heavy sheet flow runoffInstallationTracking should be done up and down the slope, not across the slope
30 Road-Side DitchesThis technique requires construction channels parallel to access roads. The ditches convey concentrated runoff of surface water from roads and surround areas to a stabilized areaLimitationsErosion occurring within channelChannel does not necessarily filter sediment from runoffInstallationExcavate channel along roadside to a width and depth that can handle expected flowsSlope channels so that water velocities do not cause excessive erosionInstall BMPs into the ditches to slow water velocities and collect sediment
32 Berm/Water BarThis technique may be used to collect runoff from undisturbed areas and divert around construction activity. Additionally, berms can be used to limit the accumulation of water volume by diverting runoff from construction area into a stabilized outlet (i.e. rundown, sediment pond) or a well-vegetated areaLimitationsNot for use on concentrated flowsMay cause concentrated flows from sheet flowRequires vegetative cover or other filter at discharge pointInstallationPile and compact soil (berms need to be compacted to hold water, prevent blow-outs and minimize vandalism/intention breaches)The side slopes should be 2:1 or flatterIncrease the frequency of water bars with an increased slopeDischarge should enter a well-vegetated cover (water bars) or a stabilized out (a constructed sediment pond)