2573Storm Water Management

2573.1DESCRIPTION

This Work consists of managing storm water runoff and Project related water discharges to minimize sediment pollution and managing the discharges associated with dewatering and basin draining activities.

2573.2MATERIALS

2573.3CONSTRUCTION REQUIREMENTS

A General Manage stormwater by routing of water, temporary diversions/flumes, bypasses, and avoidance measures. Schedule, construct, maintain, or install temporary sediment control and storm water management measures as required by the Contract. Adjust the installation location of temporary stormwater management and sediment control devices, as shown on the Plans, to better accommodate the actual field conditions and increase the effectiveness of a device. A.1 Erosion Control Supervisor Inspect and photograph dewatering operations at the beginning of dewatering and at least once every 24 hours during dewatering to ensure that the system is cleaning the water sufficient to prevent the discharge from causing nuisance conditions. Photographs must show the condition of the discharge, the discharge location, and the receiving water. Include photographs in the next stormwater inspection report.

Reduce stormwater inspection frequency to once per month in areas of the project where construction activity has been completed and the planted native vegetation has a temporary vegetation density of 70 percent. Prior to project completion take photographs of representative locations to document that all surfaces intended for permanent vegetation have a uniform cover of perennial vegetation with a density of at least 70 percent of expected cover at maturity. Submit these photos to the Engineer to be filed with the Notice of Termination . Provide an Erosion control supervisor with a valid Minnesota Erosion and Stormwater Construction Site Management certification, authorized to represent the Contractor regarding meeting contractual requirements for erosion and stormwater management and Work in public waters. The certification is obtained from a Department approved provider. The Erosion control supervisor shall be available to the Work site within 24 hours of initial disturbance and at the site daily when Work is taking place until final stabilization. The following list describes the duties of the Erosion control supervisor:

Pollution”

removal of all erosion and sediment control Best Management Practices

erosion and sediment control measures for each operation and stage of Work

undertake erosion and sediment preventive measures at each stage of the Work

inspections

shown on the Plans

for the Engineer’s approval, and amends the SWPPP per 1103, “Definitions,” or construction Plan sheets to document changes

dewatering, and temporary Work in rivers, lakes, and streams

suspension of the Work

erosion and sediment control issues resulting from the Work

locations where sediment leaves the Right-of-way

requirements

certifications per 2573.3A.2, “Certified Installers” The Erosion control supervisor is authorized to install, fix, or repair erosion or sediment control practices when a certified installer is unavailable.

A.2 Certified Installers Provide a certified installer to install or to direct installations of erosion or sediment control practices and for the following:

Provide at least one installer with a valid Minnesota Erosion and Stormwater Construction Installer Certification at the time of installation. The certification is obtained from a Department approved provider. A.3 Areas of Environmental Sensitivity Schedule and phase construction in and around Areas of Environmental Sensitivity (AES), as shown on the Plans to minimize the potential of sediment entering into these areas. Use measures such as hand clearing and grubbing, limiting bare soil exposure time, expediting construction Activities, and immediately establishing final vegetation to minimize sediment loss potential. A.4 Construction of Temporary Sediment Basins and Traps Construct temporary sediment basins concurrently with the start of soil disturbing Activities. Direct storm water runoff from drainage areas to the basins . Stabilize the exposed side slopes of the basins. Provide an outlet to the basin that discharges water from the surface, separates floatables, and provides scour protection or energy dissipation. A.5 Temporary Sediment Control Measures Install perimeter, inlet, and exit sediment control measures before, or in conjunction, with soil disturbing Activities. Recover sediment, restore property to the pre-existing conditions for loss of sediment off the Project, or both at no additional cost to the Department. A.6 Dewatering and Pumping Provide a water treatment Plan for turbid or sediment laden water. Submit the water treatment Plan to the Engineer before pumping. Do not begin Work until the Engineer accepts the water treatment Plan including any Contractor required permits. Include in the water treatment Plan the use of sediment traps, vegetative filter strips, flocculants, or other water treatments per 3875, “Water Treatment.” Protect the discharge location of the dewatering process from erosion . Unless otherwise required by the Contract, provide and install the BMPs to control erosion and suspended sediment during the dewatering or pumping operation. A.7 Suspension of Grading Shape exposed soil and incorporate temporary and Permanent Erosion Control Measures as approved by the Engineer before suspending grading operations.

A.8 Related Work Control drainage, erosion, and pollutants on the Work related to the Project including: Designated Haul Roads, temporary construction, waste disposal sites, plant and storage locations, and borrow pits other than commercially operated sources . Maintain the area, shape the area, install temporary BMPs, replace topsoil, and establish vegetative cover on areas where the potential for pollution has been increased due to the Contractor's operations . Waste disposal sites, borrow pit areas, or other related Work located outside of the Right-of-way may require separate permits. B Silt Fence Installation B.1 Type PA Preassembled Install preassembled Silt fence with attached wooden stakes in small areas less than 1/4 acre. Pound stakes at least 1.5 feet into the ground. Install the geotextile with the selvage edge on top. Place the bottom edge of the geotextile into a trench 6 inches deep and 6 inches wide. Backfill and tamp the trench for compaction. B.2 Type MS Machine Sliced Mechanically install the geotextile with the selvage edge on top . Place the geotextile directly behind the soil-slicing blade as it works to achieve consistent placement and depth. Do not plow soil if using the slicing method. Roll the wheels of a tractor or skid steer on each side of the geotextile at least 2 times to compact the soil immediately next to the geotextile. Install posts adjacent to the back face of the geotextile with the post studs facing away from the geotextile fabric. Secure each post by inserting 3 plastic ties through the geotextile. Space the posts a maximum of 6 feet on center. B.3 Type HI Hand Installed Install the geotextile by hand with the selvage edge on top in areas inaccessible by a machine. Install the bottom 8 inches to 12 inches of the geotextile with one of the following methods:

the bottom edge of the geotextile wrapping back up to the soil surface . Backfill and compact soil

on the front face and covered with crushed rock or p-gravel at least 12 inches wide and 6 inches high to provide for as a filter Install posts adjacent to the back face of the geotextile with the post studs facing away from the geotextile fabric. Insert 2 plastic ties to secure it to each post. Space the posts a maximum of 6 feet on center. B.4 Type SD Super Duty Place the bottom edge of the geotextile from 4 inches to 6 inches underneath the face of the median barrier exposed to direct storm water runoff. Place the median barriers end to end to minimize the gap between each barrier. Attach the geotextile to the face of the barrier with wire or plastic ties and tie to each eyelet on the barrier. B.5 Type TB Turbidity Barrier Use turbidity barriers to isolate the Work zone from the watercourse. Install the turbidity barrier as close to the Work area as possible but not in expected water depths greater than 2 feet deep (includes wave heights). Do not trench the geotextile into the watercourse. Anchor at least a 1 feet flap folded up-gradient with sandbags per 3893, “Sandbags,” to seal the

bottom edge. In the top edge, insert a steel support cable into a 2 inch double stitch sleeve and fastened to steel fence posts per 3403, “Hot-Rolled Steel Fence Posts.” Install posts adjacent to the back face of the geotextile with the studs facing away from the geotextile fabric. Secure each post by inserting 3 plastic ties through the geotextile. Before removing the turbidity barrier, remove and dispose of Material not originally in the isolation zone in a location approved by the Engineer. C Bale Barrier Installation Trench bales into the ground 4 inches and stake with 2 wood stakes per bale. Provide the stakes in a length that allows the placement of the stake so the top of the stakes remains flush with the top of the bale when embedded into the ground at least 10 inches. Provide Type 3 mulch per 3882 “Mulch Material, “for bale Material unless otherwise specified in the Plans. Place bale joints tight together. Provide a categories 20 or 30 rolled erosion prevention product as a wrap around the bales extending 1 foot at the base on each side. Provide staples to secure blanket to ground . D Sandbag Barrier Installation Install sandbags on a level contour. Sandbags installed a minimum of 6 feet back from the toe of the slope to allow ponding, and to provide room for sediment storage . Stack sandbags at least three bags high. Butt ends of bags tightly together and overlap butt joints of rows beneath with each successive row . Stack bags in trapezoidal shape with respect to the side profile. E Filter Berm Installation E.1 Type 1, Type 2 (Compost, Slash Mulch) For slope breaks and perimeter control, install filter berms along the contour of the slope and perpendicular to sheet flow. Install the filter berms so the beginning and end of the installation points slightly up the slope to create a “J” shape at each end to contain runoff from above and prevent it from flowing around the ends of the berm. For slopes that receive runoff from above, place a filter berm at the top of the slope to control the velocity of the flow running onto the slope, and to spread the runoff into sheet flow. For ditch checks, install perpendicular to the ditch gradient such that the top of the berm in the middle of the ditch is lower in elevation than the bottom of the terminating points on the ditch side slopes. Upon formation, immediately seed compost filter berms. E.2 Type 3 (Rock Weeper) Line the bottom of the rock weeper with a Type IV geotextile per 3733, “Geosynthetic Materials.” Provide a rock weeper that forms a trapezoidal-shaped berm. Install coarse filter Aggregate per 3149, “Granular Material,” on the front half of the berm. Install Class I riprap per 3601, “Riprap Material,” on the back half of the berm. For ditch checks, install perpendicular to the ditch gradient. Construct the center section of the rock weeper 6 inches lower than the end points of the weeper at the ditch side slopes to form a weir. For permanent ditch checks, reduce the height to 16 inches and modify the side slopes to 1:6 (Vertical:Horizontal).

E.3 Type 4 (Topsoil) For perimeter control, construct a topsoil berm using topsoil salvaged from the P roject. Immediately following formation, stabilize the berm with seed and mulch or an equivalent approved by the Engineer. E.4 Type 5 (Rock) Install Class II riprap on top of a Type IV geotextile liner per 3733, “Geosynthetic Materials.” Configure riprap in a trapezoidal-shaped berm. For ditch checks, install perpendicular to the ditch gradient . Construct the center section of the rock berm 6 inches lower than the end points of the rock berm at the ditch side slopes to form a weir. For permanent ditch checks reduce the height to 16 inches and modify the side slopes to 1:6 (Vertical:Horizontal). F Sediment Control Log Installation F.1 Straw, Wood Fiber, and Coir Place logs on smooth prepped soils and prepare a shallow trench for the sediment control log to be placed. Backfill and compact the upgrade side of the sediment control log with soil. Stake logs through the back half of the log at a 45 degree angle with the top of the stake pointed upstream. Stakes shall be spaced every 2 feet. If using more than 1 sediment control log for length, overlap the ends 6 inches and stake both ends. F.2 Wood Chip, Compost, and Rock Place logs on smooth, prepped soils or paved surfaces and ensure no gaps are between logs and soil or paved surface. Install logs along contours with ends turned up slope in a J -hook manner. F.3 Wood Fiber and Blanket System For Ditch checks install rolled erosion prevention category 25 per 3885, “Rolled Erosion Prevention Products,” (REPP) or as shown in Plan, at least 1 role width, perpendicular to the ditch flow. Bury the leading edge in a trench 4 inches deep and 4 inches wide. Backfill and compact the trench with soil. Staple the REPP at spacing no greater than 1 foot on center. Place the sediment control log type wood fiber per 2573.3F.3, “Wood Fiber and Blanket System,” without the trench, on top of the REPP. If using more than 1 sediment control log for length, overlap the ends 6 inches and stake both ends. Follow additional ditch check installation as per 2573.3F.4, “Ditch Checks.” F.4 Ditch Checks Follow installation above for sediment control log type wood fiber, wood chip, compost, or rock and place perpendicular to flow and in a crescent shape with ends facing upstream. Use logs with a center section of the ditch check 1 log diameter lower than the ends. Space stakes every 1 foot. Provide 2 stakes in a crisscross pattern at each location with the sediment control log in-between. G Flotation Silt Curtain Installation Provide a flotation silt curtain meeting the following requirements and characteristics:

connection and at the specified strength to prevent ripping out

G.1 Still Water Secure both ends of a light duty floating silt curtain to land with steel fence posts per 3403, “Hot-Rolled Steel Fence Posts,” and extend the curtain at a 45 degree angle from both ends. Anchor the curtain in the waterway with at least 40-pound anchors at intervals no greater than 100 feet along the length of the curtain. Mark each anchor with a buoy in navigable waters. Keep the curtain as tight to the Work area or shoreline as possible not to exceed 1/4 of a stream width. G.2 Moving Water Secure both ends of a heavy duty floating silt curtain per 3887, “Flotation Silt Curtain,” to land with steel fence posts per 3403, “Hot-Rolled Steel Fence Posts,” and extend the curtain at a 45 degree angle from both ends. Anchor the curtain in the waterway with at least 150-pound anchors at intervals no greater than 50 feet along the length of the curtain. Mark each anchor with a buoy in navigable waters. Keep the curtain as tight to the Work area or shoreline as possible not to exceed 1/4 of a stream width. H Construction Exit Controls Select Exit controls from the following list of stabilized construction exits:

Use construction exit control BMPs at exit locations to minimize vehicle tracking of sediment from the Project onto paved surfaces. Install BMPs during the initial phase of the Project. Select construction exit BMP based on Project Site conditions, soil type, vehicle size, time of year, and duration of use. Used Materials generated by the Project as construction exit controls whenever possible. Maintain exit controls during the Project. Clean paved Streets at the end of each Working Day, or more frequently as necessary to provide safety to the traveling public. H.1 Wheel Wash Off Provide a wheel wash off system in addition to stabilized exit controls when P roject Site conditions warrant. I Culvert End Controls I.1 Inlet Provide Culvert inlet end sediment trap and volume controls consisting of the BMPs and devices for temporary impoundment and treatment of construction stormwater upstream. Culvert inlet end controls apply to median Culverts, centerline Culverts, box Culverts, and entrance Culverts. I.2 Outlet Provide Culvert outlet ends with energy dissipation devices, transition devices, or both.

J Storm Drain Inlet Protection Implement BMPs and devices to protect storm drain inlets for all stages of W ork to prevent passage of sediments into and through underground drainage systems. Protect storm drain inlets, including manholes, catch basins, curb inlets, and other type inlets constructed for the ingress of surface water runoff into underground drainage systems. Install storm drain inlets with sediment capture devices before soil disturbing activities . Provide effective storm drain inlet protection until the completion of paving or final stabilization of soils. Prevent or minimize the potential for unsafe flooding or siltation problems . Clean out devices regularly and provide devices with an emergency overflow to reduce the flooding potential . Place devices without creating driving hazards or obstructions. K Flocculants Apply flocculants in conjunction with installed sediment and erosion control BMPs . Do not apply flocculants directly to public waters (i.e. lakes, wetlands, streams). Apply flocculants in a contained area and assure thorough mixing into the water. Before applying a flocculant, test the pH and temperature of the storm water. Apply flocculant within the manufacturer's specified ranges. Allow from 15 to 20 minutes retention time for clay size particles to settle, ensuring that the discharge of the treated water is visually the same as the receiving water. K.1 Liquid Flocculant Hydraulically apply liquid flocculant over the surface of the water to be treated. Dilute the liquid flocculant concentrate to form a stock solution. Apply the stock solution at the manufacturer’s recommended rate to yield 1 ppm in the final treated water volume. K.2 Flocculant Sock Securely anchor the flocculant sock in an area where the water to be treated will flow over the sock. Do not leave flocculant socks in standing, stagnant water. K.3 Granular Flocculant Mix granular based flocculant with water in a tank to form a stock solution . Hydraulically apply the stock solution at the manufacturer’s recommended rate to yield 1 ppm in the final treated water volume. L Temporary Slope Drains Provide temporary slope drains to convey concentrated runoff down the face of a cut or fill slope to reduce erosion on or below the slope. Provide a minimum slope on pipe of 3 percent. Size the pipe to the appropriate drainage area. Maximum allowable drainage area is 5 acres per slope drain. Provide an earthen dike to channel the flow to the temporary slope drain. Construct the top of the earth dike 1 foot higher than the top of the inlet pipe. Provide anchors for the pipe and space no greater than 8 feet apart. Use a watertight connection to attach the flared end section to the inlet end of drain pipe . Extend temporary pipe beyond the toe of slope and terminate in a 4 foot level section where practicable. Provide a riprap apron outlet and sediment trap for energy dissipation. M Maintenance Keep all devices functioning properly and maintained in accordance with the Contract . Repair or replace plugged, torn, displaced, damaged, or nonfunctioning devices. Remove sediment from sediment control devices when the sediment reaches 1/2 of the height of the device. Replace or repair devices damaged or compacted by Equipment. Perform repair or sediment removal within 24 hours of discovery or as soon as field conditions allow access.

M.1 Filter Berms Expand, enlarge, or augment the filter berm with additional erosion and sediment control practices if concentrated flows bypass or breach the berm or to maintain the dimensions of the berm. M.2 Sediment Basins and Traps Drain the basin and remove the sediment when the depth of sediment collected in the basin reaches 50 percent of the storage volume determined by the outfall device. Complete drainage and removal within 72 hours or as soon as field conditions allow access. Remove sediment to the original designed or excavated grade or as necessary to restore the function of the device. Restore stabilized condition of side slopes and access R oad. Clean out and shape temporary sedimentation basins intended for use as permanent water quality management basins as shown on the Plans. M.3 Storm Drain Inlet Protection Devices Clean, remove sediment, or replace storm drain inlet protection devices on a routine basis to ensure the full functionality of the devices for the next rainstorm event. M.4 Culvert Inlet End Control Devices Clean, remove sediment, or replace Culvert inlet end control devices on a routine basis to ensure the full functionality of the devices for the next rainstorm event. N Water Treatments Use properly sized floating head skimmers to withdraw collected waters from the surface. Tether floating skimmer to maximize surface water withdraw and maintenance functionality. Install stop system to prevent floating head embedment into sediment. Install and attach skimmer pipe outfall to new or existing Structure, berm underdrain, or as site conditions allow. O Removal of Temporary Devices Remove temporary sediment control devices after completing the W ork unless otherwise required by the Contract or directed by the Engineer. All removed Materials become the property of the Contractor. Spread accumulated sediment to form a suitable surface for turf establishment or dispose of the sediment. Shape the area to permit natural drainage as approved by the Engineer. Remove the Silt curtain upon completion of Work. Do not allow resuspension of sediment or loss of trash and oil into the water during the Silt curtain removal. Remove sediment control logs upon completion of Work. Outer shell Material must be removed completely and contents of logs may be left in place and spread out over the ground to decay. P Workmanship and Quality To qualify for payment, perform corrective actions when the quality and workmanship fails to meet the Material, installation, or maintenance requirements in the Contract.

2573.4METHOD OF MEASUREMENT

A Bale Barriers The Engineer will measure the bale barriers by the length installed. The rolled erosion prevention product wrap is included in the linear measurement.

B Silt Fence The Engineer will measure Silt fence along the base of the fence from outside to outside of the end posts for each section of fence. C Sandbag Barriers The Engineer will measure sandbag barriers by surface area based on actual measurement taken along the length of the barrier times its height. If the Contractor installed more than 1 thickness of sandbags the Engineer will measure the surface area of each Layer of thickness and add it to the quantity. D Flotation Silt Curtain The Engineer will measure flotation Silt curtain by length installed. E Temporary Sediment Traps The Engineer will measure sediment trap excavation by volume. The Engineer will measure overflow devices separately. F Temporary Slope Drains The Engineer will measure temporary slope drains by length installed. The diversion mound a nd apron inlet of the pipe are included in the Pay Item temporary slope drain. The Engineer will measure Materials used to provide an outlet separately. G Sediment Removal The Engineer will measure sediment removal from temporary sediment traps and basins by backhoe hours or vac-truck hours. The spreading and hauling of sediment are included in the Pay Item sediment removal. H Sediment Control Logs The Engineer will measure types; straw, wood fiber, coir, wood chip, compost, and rock, by the effective length installed. The Engineer will not include overlaps in the measurement. The Engineer will measure types; wood fiber and blanket system by length installed. The Engineer will not include overlaps in the measurement. I Culvert Inlet End Controls I.1 Each The Engineer will measure Culvert inlet end controls by measuring the number of individual Culvert inlet ends protected throughout the Work regardless of the type or number of devices used at each Culvert end. J Storm Drain Inlet Protection J.1 Each Storm Drain inlet The Engineer will measure storm drain inlet protection by the number of individual inlets protected over the life of the Contract regardless of the types of number of devices used at each storm drain inlet. J.2 Lump Sum The Engineer will measure storm drain inlet protection as lump sum. Lump sum shall include all Materials and labor necessary to provide proper inlet protection through the life of the Contract regardless of quantities and types required. K Flocculants The Engineer will measure liquid flocculant by the volume of liquid flocculant concentrate used . The Engineer will not include the water used to dilute the concentrate.

The Engineer will measure flocculant sock by each provided. The Engineer will measure granular flocculant by the weight used and placed. The Engineer will not include the water used to dissolve and dilute the granular flocculant. L Construction Exit Controls The Engineer will measure construction exit controls by the lump sum including the cost of protecting each exit over the life of the Contract regardless of types or quantities. Wheel wash of systems will be measured separately. M Water Treatment The Engineer will measure floating head skimmer by the each that includes the cost of size determination and associated Material, Work, and connections to the outfall drainage Structures for the life of the Contract regardless of adjustments made for rate control and sediment accumulation.

2573.5BASIS OF PAYMENT

The Contract Pay Items for stormwater management will include the Material, Equipment, installation, maintenance, and removal as required by the Contract to complete the Work. For items of Work not included in the schedule of Contract Pay Items, the Department will pay Unit Prices for the relevant items of Work. The Department will provide partial payment of temporary sediment control devices properly installed at no greater than 50 percent of the Contract Unit Price for each relevant Pay Item unless otherwise required by the Contract. The Department will pay the remaining partial payment after proper maintenance and removal of the device. The Department will withhold from monies owed to the Contractor for each improperly installed or maintained device where the Contractor failed to remove sediment, and the Engineer has ordered this corrective action. A Filter Berms The Contract Pay Item for topsoil Filter berm includes seed and mulch. The Contract Pay Item for rock or rock weeper filter berm when converted from temporary to permanent conditions includes the cost to modify the berm dimensions . B Storm Drain Inlet Protection The Contract Pay Item for the inlet protection devices includes the cost of removing and disposing of trapped sediment or sediment deposited in or plugging drainage systems protected by the devices. C Silt Fence The Contract Pay Item for the Silt fence includes removal and disposal of trapped sediment. The Department will withhold from monies owed to the Contractor for each section of S ilt fence not maintained at discharge points or where damaged by the public or the Contractor, and the Engineer has ordered this corrective action. D Water Treatments The lump sum price for Water treatments includes the development of the water treatment Plan, protection of trees, repair and replacement of damaged sections, and removal of sediment deposits. E Construction Exit Controls The wheel wash systems will be paid for separately for each system.

F Sediment Traps The Department will pay for removal of sediment from sediment traps by backhoe or vac -truck by the hour. Sediment spreading and disposal are included in the P ay Item sediment trap excavation. G Erosion Control Supervisor The Department will provide partial payment no greater than 50 percent of the Contract lump sum price for Erosion control supervisor upon satisfactory completion of either half the allowable Project Working Days or half the anticipated Project duration time as approved by the Engineer. If providing partial payment, the Department will pay the remaining percentage upon performance of duties as approved by the Engineer and completion of the Work. The Department will withhold from monies owed to the Contractor for failure to provide a certified Erosion control supervisor or failure to perform Erosion control supervisor duties. H Schedule The Department will pay for temporary sediment control items on the basis of the following schedule: Item No. Item Unit

2573.501 Erosion Control Supervisor lump sum

1 Water Treatment lump sum

1 Stabilized Construction Exit lump sum

1 Storm Drain Inlet Protection lump sum

2 Culvert End Control each

2 Flocculant Sock each

2 Storm Drain Inlet Protection each

2 Water Treatment Type ___ each

2 Wheel Wash Off each

3 Bale Barrier linear foot

3 Filter Berm Type ___ linear foot

3 Floatation Silt Curtain Type ___ linear foot

3 Sediment Control Log Type ___ linear foot

3 Silt Fence, Type ___ linear foot

3 Temporary Slope Drain linear foot

6 Liquid Flocculant gallon

7 Sediment Trap Excavation cubic yard

8 Granular Flocculant pound

2573.510 Sediment Removal Backhoe hours

0 Sediment Removal Vac Truck Hours

8 Sandbag Barrier square foot