316 STORMWATER MANAGEMENT (SWM) FILTRATION FACILITIES

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316.01 DESCRIPTION
Construct stormwater management (SWM) filtration facilities as specified.
SWM Filtration Facilities Identification. SWM filtration facilities are identified by unique six-digit inventory numbers and include the following designations.
(a) Bioretention.
(b) Micro-Bioretention.
(c) Organic Filters.
(d) Surface Sand Filters.
(e) Submerged Gravel Wetlands.
(f) Landscape Infiltration.
(g) Rain Gardens.
(h) Infiltration Berms.
(i) Bio-swales.
316.02 MATERIALS
No. 57 Aggregate       901.01
No. 7 Aggregate       901.01
No. 2 Aggregate       M 43, No. 2
Portland Cement Concrete       902.10, Mix No. 2
Topsoil       920.01.01 and 920.01.02
Bioretention Soil Mix (BSM)       920.01.05
Coarse Sand       920.01.05(a)(1)
Fertilizer       920.03.01
Shredded Hardwood Bark (SHB) Mulch       920.04.03
Soil Stabilization Matting (SSM)       920.05
Seed and Turfgrass Sod       920.06
Plant Materials       920.07
Water       920.09.01
Geotextile       Section 919, Class PE, Type III
Securing Pins or Staples       Section 919
Aggregate. Ensure aggregate has been adequately washed and is free of soil and fines.
316.02.01 Subdrain Pipe, Fittings and Geotextile Sock. . Subdrain pipe shall include slotted perforated and solid-wall (non-perforated) pipe. Perforated subdrain pipe shall have only two rows of perforations. Use fittings matching the same material as the subdrain pipe and is otherwise compatible with the subdrain pipe. Use subdrain pipe, fittings, and geotextile sock for subdrain, cleanouts, and observation wells.
(a) Subdrain Pipe.Pipe material for perforated subdrain pipe may be one of the following.
(1) Polyvinyl chloride (PVC) profile wall drain pipe (PPWP) with soiltight joints, slotted perforations not to exceed 0.12 in. in width with a minimum water inlet area of 1 in.2/ft (for pipe diameters 6 in. to 10 in.) or 1.5 in.2/ft (for 12 in. diameters), and meeting M 304.
(2) Corrugated polyethylene drainage pipe (CPP) Type SP with Class 2 slotted perforations having a minimum water inlet area of 1 in.2/ft (for pipe diameters 3 in. to 10 in.), and meeting M 252.
(b) Subdrain Pipe Cleanouts. Pipe material for non-perforated or solid wall subdrain pipe used for cleanouts may be one of the following and compatible with the subdrain pipe used in 316.02.01(a).
(1) Polyvinyl chloride (PVC) profile wall drain pipe (PPWP) with soiltight joints and meeting M 304.
(2) Corrugated polyethylene drainage pipe (CPP) Type S and meeting M 252.
(c) Observation Wells. Pipe material used for observation wells shall be as specified in 316.02.01(a) for the perforated portion of observation wells and 316.02.01(b) for the solid-wall portion of observation wells. Use the geotextile sock recommended and supplied by the subdrain pipe manufacturer and use only to cover the perforated pipe portion of observation wells.
316.03 CONSTRUCTION
316.03.01 Site Protection. Prior to constructing SWM filtration facilities, ensure that the SWM facility site areas are protected from vehicular traffic and is not used for erosion and sediment controls, stockpiles or equipment storage.
316.03.02 Site Preparation. Unless facilities are off-line and will receive no runoff, construct facilities only after all surrounding and adjacent areas are permanently stabilized. Divert flow from entering the SWM filtration facility areas unless same-day stabilization is specified for the SWM filtration facility location. Prevent trash, debris and sediment from entering SWM filtration facilities during construction.
316.03.03 Schedule. Perform SWM filtration facility activities during dry weather and when soil moisture conditions are suitable and unless the facility is off-line or flow diversions are in place. Only work with soil that is friable and not in a muddy or frozen condition. Cease operations when soil and overall conditions are otherwise unsuitable.
316.03.04 Excavation. Use methods of excavation that minimize compaction of the underlying soils. Where feasible, operate equipment from locations adjacent to SWM filtration facilities rather than within the facility area. Use only wide-track or marsh-track equipment, or light equipment with turf-type tires to excavate, grade, and place materials. Do not use equipment with narrow tracks or narrow tires, rubber tires with large lugs, or high-pressure tires.
316.03.05 Excavation Area Bottom Preparation. Only work with soil that is friable and not in a muddy or frozen condition. When present, remove any standing water from the excavation area. Prepare the bottom of the excavated area as follows.
(a) Submerged Gravel Wetlands. Rake surface to loosen soil.
(b) All Other SWM Filtration Facilities. Till to a minimum depth of 8 in. to loosen soil.
316.03.06 Geotextile. Place tightly against the vertical sides of the excavation area, pulling tight to eliminate wrinkles and folds and pin securely. Eliminate any voids between the geotextile and the underlying soil and avoid wrinkling and folding the geotextile. Maintain a minimum 12 in. overlap at the geotextile joint ends or breaks. Pin longitudinal joints, overlaps and edges securely with pins spaced no greater than 10 ft on center. Do not place geotextile on the bottom of the excavated area.
316.03.07 Miscellaneous Structures. Furnish and install as specified in Section 305.
316.03.08 Aggregate. Place aggregate in layers as specified. Prevent soil, fines, and other debris from contaminating the aggregate. Remove contaminated aggregate and replace with clean aggregate.
316.03.09 Subdrain Pipe. Cap the ends of all subdrain pipe not terminating in a cleanout, vent, or drainage structure unless otherwise specified. Ensure perforations are placed on the bottom of the horizontal subdrain pipe runs.
(a) Cleanouts. Install solid-wall pipe vertically and connect to horizontal subdrain with approved manufactured connections. Provide a counter-sunk screw cap on the exposed ends.
(b) Vents. Install solid-wall pipe vertically and connect to the horizontal subdrain with approved manufactured connections. Provide a ventilated screw cap on the exposed ends. Ventilation holes or slots shall be no larger than 1/4 in. in diameter or width. The sum total area of the openings shall be no less than 1 in2. Ensure that the ventilation openings are above the maximum specified water surface elevation.
(c) Observation Wells. Use perforated and solid-wall pipe. Place the geotextile sock over the perforated pipe portion and secure at both ends. Provide a screw cap on the exposed end extending 2 in. above the surface. When a concrete collar is specified, ensure the top of the well is flush with the surface of the concrete collar.
316.03.10 Coarse Sand. Place coarse sand in horizontal layers not exceeding 12 in. After each lift, spread the coarse sand to provide a uniform surface then spray or sprinkle water to saturate the lift until water flows from the subdrain outlet. Use an appropriate sediment control device to capture any discharged sediment-laden water from the subdrain outlet. Place, spread, and water coarse sand to uniform surface true to depth, line, cross section and elevation to ensure the completed work is as specified after settlement. Prevent soil, fines and other debris from contaminating the coarse sand. Remove contaminated coarse sand and replace with clean coarse sand.
316.03.11 Bioretention Soil Mix (BSM). Place BSM in horizontal layers not exceeding 12 in. After each lift, spread the BSM to provide a uniform surface and spray or sprinkle water to saturate the entire area of BSM until water flows from the subdrain outlet. Use an approved sediment control device to capture any discharge sediment-laden water. Place, spread, and water BSM to uniform surface true to depth, line, cross section and elevation to ensure the completed work is as specified after settlement. Prevent soil, fines, and other debris from contaminating the BSM. Remove contaminated BSM and replace with uncontaminated BSM.
316.03.12 Topsoil. Place topsoil as specified. Do not blend topsoil into BSM when topsoil is placed on top of BSM.
316.03.13 Check Dams.
(a) Topsoil Check Dams. Construct topsoil check dams to the dimensions, grades, and depths specified.
(b) Concrete Check Dams. Furnish and install concrete check dams as specified and as specified in Section 305.
316.03.14 Soil Stabilization Matting (SSM). As specified in Section 709.
316.03.15 Vegetation Installation and Establishment. Unless facilities are off-line or flow diversions are in place, install seed, sod, trees, shrubs, perennials, and annuals within SWM filtration facility areas immediately after final grading. In the event that vegetation cannot be installed and established due to time-of-year or weather restrictions, keep diversion controls in place until such time that permanent vegetation may be established. Do not use machinery other than hand held within the BSM footprint.
(a) Turfgrass Establishment. As specified in Section 705.
(b) Meadow Establishment and Wildflower Seeding. As specified in Section 707.
(c) Turfgrass Sod Establishment. As specified in Section 708.
(d) Tree, Shrubs and Perennial Installation and Establishment. As specified in Section 710.
(e) Annuals & Bulb Installation and Establishment. As specified in Section 711.
316.03.16 Soil Amendments and Fertilizer. Apply as specified in Sections 705, 706, 707, 708, 710, or as specified. Use the following for plant materials installed in BSM.
(a) Non-Vegetated BSM. Do not apply compost, other soil amendments, or fertilizer to non-vegetated BSM.
(b) Trees, Shrub, and Perennials in BSM. Do not apply compost or other soil amendments to backfill soil or to planting beds.
Apply fertilizer to each planting pit as specified in 710.03.04 when trees, shrubs, perennials, perennial plugs, or other plant materials are installed in BSM as specified in Section 710.
(c) Seeded or Sodded BSM. Do not apply compost or other soil amendments.
Uniformly apply either of the fertilizers in Table 1 at the rate specified over the installed surface of the BSM when BSM will be permanently vegetated with Turfgrass Establishment, Shrub Seeding Establishment, Meadow Establishment, Turfgrass Sod Establishment, or other seeded or sodded vegetation establishment as specified.
BIORETENTION SOIL MIX

TABLE 1 - FERTILIZER APPLICATION RATES

FERTILIZER LB PER SY LB PER ACRE
20-16-12 (83% UF with MAP and SOP) 0.052 200
14-14-14 polymer coated or granular 0.062 275
(d) Nutrient Management Reporting. Record the fertilizer analysis, the square yards covered, and the pounds of fertilizer applied on the Nutrient Management Reporting Form. Submit the Form within 24 hours after applying fertilizer.
(e) Fertilizer. Refer to (b). Rake fertilizer that is broadcast over the surface of the BSM for seeding or sodding to a depth of 1/8 in. to 1/2 in. Raking may be performed as part of seeding or sodding operations. Complete raking before soil stabilization matting or sod is installed.
316.03.17 Shredded Hardwood Bark (SHB) Mulch. As specified in 710.03.13.
316.03.18 Inspection and SWM Facility As-Built Certification. Inspect and document each step of construction of SWM filtration facilities and complete the applicable checklists and furnish the SWM facility as-built certification according to the Contract Documents.
316.04 MEASUREMENT AND PAYMENT
Payment will be full compensation for all control of discharge from subdrain pipe, geotextile, watering, sheeting, shoring, dewatering, hauling, storing, re-handling of material, removal and disposal of excess and unsuitable material, tilling, grading and slope adjustments and for all material, labor, equipment, tools, and incidentals necessary to complete the work.
Excavation. Excavation will be measured and paid for as specified in Section 201.
Miscellaneous Structures. Miscellaneous Structures will be measured and paid for per cubic yard of the specified mix concrete.
Aggregate. Aggregate will be measured and paid for at the Contract unit price for one or more of the following.
(a) No. 2 Aggregate for Stormwater Management Facilities per cubic yard.
(b) No. 7 Aggregate for Stormwater Management Facilities per cubic yard.
(c) No. 57 Aggregate for Stormwater Management Facilities per cubic yard.
Removal of contaminated aggregate and replacement with clean aggregate will be at no additional cost to the Administration.
Geotextile. Geotextile will not be measured but the cost will be incidental to the excavation.
Subdrain Pipe. Perforated and solid-wall subdrain pipe will be measured and paid for at the Contract unit price per linear foot for the specified size of subdrain pipe. Fittings, caps, geotextile sock, cleanouts, vents, observation wells, and other incidentals will not be measured but the cost will be incidental to the subdrain pipe.
Coarse Sand. Coarse Sand will be measured and paid for at the Contract unit price per cubic yard for Coarse Sand for Stormwater Management Facilities.
Removal of contaminated coarse sand and replacement with uncontaminated coarse sand will be at no additional cost to the Administration.
Check Dams. Check dams will be measured and paid for at the Contract unit price for one or more of the following.
(a) Topsoil Check Dams per each.
(b) Concrete Check Dams per each.
Bioretention Soil Mixture (BSM). BSM will be measured and paid for at the Contract unit price per cubic yard.
Removal of contaminated BSM and replacement with clean BSM will be at no additional cost to the Administration.
Water. Water used for saturation of coarse sand and BSM will not be measured but the cost will be incidental to the pertinent items.
Shredded Hardwood Bark (SHB) Mulch. SHB Mulch will be measured and paid for at the Contract unit price per square yard for Shredded Hardwood Bark Mulching, 3 in. depth.
Sediment Control for Discharge from Subdrain Pipe Outlets. Control for any sediment-laden discharge from subdrain pipe outlets will not be measured but will be incidental to the pertinent Erosion and Sediment Control items.
Topsoil. As specified in 701.04.
Vegetation Installation and Establishment. Vegetation installation and establishment will be measured and paid for at the Contact unit price for the pertinent landscaping items as specified in 705.04, 707.04, 708.04, 710.04 and 711.04.
Soil Stabilization Matting. As specified in 709.04.
Stormwater Management (SWM) Facility As-Built Certification. As specified.