Stormwater Manual - Pima County Flood Control District

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Upon removal of the structure, the stream shall immediately be reshaped to its original cross section and properly stabilized. The approaches to the structure shall consist of stone pads with a minimum thickness of 6 inches, a minimum width equal to the width of the structure, and a minimum approach length of 25 feet on each side. Maintenance The structure shall be inspected after every rainfall and at least once a week and all damages repaired immediately. 11.5.8 Pump-Around Flow Diversion Pump-around flow diversions must be used to divert flow during excavation operations in streams. Pump-around flow diversions provide dry working conditions during construction in streams. Diverting stream flow around the work area prevents suspension of sediment in stream flow by construction activities. See Figure 11-27 for an illustration of a pump-around flow diversion. Design Criteria Size the diversion pump based on normal stream flow. Dewatering pump should be sized based on the size of the work area, the time allowed for dewatering, and the expected rate of groundwater flow into the excavation. The check dams to form the diversion shall span the banks of the stream. Maintain 1-foot freeboard (minimum) on the upstream and downstream checks. Check dams may be constructed of sandbags or may be a water-filled bladder such as an Aqua-Barrier. The dewatering flow from the work area must be treated in a sediment-trapping device prior to discharge to the stream. Material Specifications Sandbags shall be woven polypropylene bags with approximate dimensions of 18-1/2 inches by 28 inches. Tie the ends of filled bags closed using either draw strings or wire ties. Construction Procedures and Specifications Schedule operations such that diversion installation, in-stream excavation, in-stream construction, stream restoration, and diversion removal are completed as quickly as possible. Do not construct in a stream when rainfall is expected during the time excavation will be occurring in the stream. Install check dams across the stream during low flow conditions. STORMWATER MANUAL 11-47 August 29, 2011 LEXINGTON-FAYETTE CO., KY.
Pump stream flow around the check dams. discharge. Install outlet protection as required at the Dewater the work area and pump into a sediment trapping device. Complete construction activities across the stream. Restore the streambed and banks. Remove sandbags and shut down pumping operation. (Salvage sandbags for future use if multiple stream crossings are required on the project.) Remove all sandbags from the stream, including damaged and empty bags. Pumps shall be manned around-the-clock when the pump-around diversion is in the stream. Maintenance This control provides short-term diversion of stream flow (typically 1 day to 3 days). Additional sandbags or pumps may be required to maintain 1-foot freeboard on the sandbag checks if flow conditions change. Add sandbags as required to seal leaks in checks. 11.5.9 Construction Dewatering Dewatering is the pumping of stormwater or groundwater from excavation pits or trenches. The sediment-laden water must be pumped to a dewatering structure before it is discharged offsite. The purpose of a dewatering structure is to remove sediment from the water before it is discharged. Design Criteria There are several types of dewatering structures that may be used. A well-stabilized vegetated area may serve as a filtering structure if it can withstand the velocity of the discharged water. The minimum filter length must be at least 75 feet. Other methods that may be used include a sediment trap/basin, portable sediment tank, a straw bale/silt fence pit, or a commercial sediment filter bag. The structure must be sized to allow pumped water to flow through the structure without overtopping. Construction Specifications See the specifications in this manual for sediment traps and basins. The manufacturer’s recommendations should be followed for commercial products. Maintenance The dewatering structure should be inspected frequently to ensure it is functioning properly and not overtopping. Accumulated sediment should be spread out on site and stabilized, or disposed of offsite. STORMWATER MANUAL 11-48 August 29, 2011 LEXINGTON-FAYETTE CO., KY.
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Stormwater Manual Lexington-Fayette
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1.1 Introduction Chapter 1 gives th
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1.3 Definitions 1.3.1 Public Draina
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• the Division of Engineering det
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• Masterson Station Watershed hyd
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• only one corporation or busines
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1.5 Water Quantity Criteria for New
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TABLE 1- 1 OPTIONS FOR STORMWATER M
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TABLE 1- 2 FLOW CRITERIA FOR STORMW
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contained in Chapter 10. The water
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1.7.4 Water Quality Criteria for Re
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• new development commercial site
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CHAPTER 2 PERMITS
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2.1 Land Disturbance Permit 2.1.1 P
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If the analysis described in the de
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2.3 Kentucky Division of Water KPDE
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2.5 401 and 404 Permits - Kentucky
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3.1 Introduction Watershed studies
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• detailed description of any nat
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3.3 Runoff Models 3.3.1 General The
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3.4 Post-Development Floodplain Ana
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APPENDIX 3-A - SOURCES OF DATA
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National Oceanography and Atmospher
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Pond/Culvert Inventory Data Sheet P
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4.1 Overview 4.1.1 Introduction An
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4.3 Improvement Plans 4.3.1 50 Perc
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• culvert outlet appurtenances an
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4.4 Record Drawings A record drawin
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5.1 Introduction 5.1.1 Purpose The
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5.3 Design Rainfall Event 5.3.1 Sin
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TABLE 5- 2 GREEN-AMPT INFILTRATION
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5.5 Stormwater Management Model (SW
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TABLE 5- 4 MANNINGS N FOR OVERLAND
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APPENDIX 5 A DESIGN STORM DISTRIBUT
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6-HOUR RAINFALL DISTRIBUTIONS Cumul
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100-YEAR - 24-HOUR RAINFALL DISTRIB
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CHAPTER 6 INLETS / STORM SEWERS / M
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6.1.4 Storm Sewers Storm sewers sha
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For d ≥ 1.0’, use the orifice f
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6.4 Construction Specifications All
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7.1 Introduction As used in this ma
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7.2.6 Culvert Skew A culvert shall
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Barrel Area and Shape Barrel area i
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7.5 Bridge Design Procedures Use HE
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CHAPTER 8 CONSTRUCTED CHANNELS
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8.2 Permanent Constructed Channels
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The earth fill materials used to co
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8.3 Paved Channels A paved channel
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9.1 Introduction The streams of Fay
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9.2.3 Material Specifications Veget
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TABLE 9- 1 SUGGESTED RIPARIAN SPECI
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9.3 Riparian Buffer Zones 9.3.1 Gen
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9.4 Bioengineering Techniques Bioen
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9.4.3 Root Wad Revetment Root wad r
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Dead stout stakes shall be installe
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Willow tree species are the best fo
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9.5.3 Maintenance All structures sh
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10.1 Introduction Non-point source
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TABLE 10- 1 WATER QUALITY DEPTH VER
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Grade the top of the planting soil
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10.4 Infiltration Systems Infiltrat
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Design Criteria To be considered a
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If desired, large infiltration basi
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When the contributing area draining
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Provide sufficient access to the de
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Select underdrain gravel to meet AA
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Compute the total surface area of b
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10.6 Prefabricated Treatment Device
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landscaping plan for the pond and t
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When necessary, compact subgrade su
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After the embankment has been built
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Embankment heights shall not exceed
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10.9 Wet Ponds In this manual, wet
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Q = A (2gH) 0.5 /(1 + K e +K b + K
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Provide a drain with a valve at the
Page 180 and 181: CHAPTER 11 EROSION AND SEDIMENT CON
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Page 190 and 191: peak discharges during construction
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Page 194 and 195: 11.4 Structural Soil Stabilization
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Page 198 and 199: Material Specifications Seed shall
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Page 204 and 205: To reduce maintenance and loss of a
Page 206 and 207: Effective netting and matting requi
Page 208 and 209: Maintenance Outlets shall be inspec
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Page 212 and 213: A standard flared end section or a
Page 214 and 215: 11.5 Structural Sediment Control BM
Page 216 and 217: The amount of sediment entering a t
Page 218 and 219: Detention storage shall be provided
Page 220 and 221: The emergency spillway shall have a
Page 222 and 223: PHYSICAL PROPERTY Filtering Efficie
Page 224 and 225: Fasten fabric securely to the stake
Page 226 and 227: SEEDING MIXTURE AND SITE SUITABILIT
Page 230 and 231: 11.5.10 Concrete Washout Pits Concr
Page 232: Inspection of Sediment Controls The
Page 261 and 262: 12.1 Introduction As Fayette County
Page 263 and 264: 12.2 Dry Detention Pond 12.2.1 Desc
Page 265 and 266: 12.3 Dry Extended Detention Pond 12
Page 267 and 268: 12.4 Wet Detention Pond 12.4.1 Desc
Page 269 and 270: 12.5 Constructed Wetlands 12.5.1 De
Page 271 and 272: 12.6 Biofiltration Practices 12.6.1
Page 273 and 274: 12.7 Infiltration Practices 12.7.1
Page 275 and 276: 12.8 Modular Pavement 12.8.1 Descri
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1Lexington-Fayette Urban County Gov
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2Infiltration Basin Maintenance Ins
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3Infiltration Swale Maintenance Ins
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Action to be taken: If any of the a
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6Filtration Facility Maintenance In
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Summary of Changes to the LFUCG Sto
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11.5.5 Storm Drain Inlet Protection
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Stormwater Manual - Pima County Flood Control District

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