Loading...
HomeMy WebLinkAboutRES 99-369 RESOLUTION NO. BE IT RESOLVED BY THE CITY COUNCIL OF THE CITY OF BEAUMONT: THAT the City Council hereby approves acceptance of the National Pollution Discharge Elimination System (NPDES) guidance document attached hereto as Exhibit W. PASSED BY THE CITY COUNCIL of the City of Beaumont this the / day of 1999. CiL yv. f - Mayor - GUIDELINES FOR INCLUSION OF WATER QUALITY CONTROL STRUCTURES AND THE ASSESSMENT OF POTENTIAL WATER QUALITY IMPACTS IN-FLOOD CONTROL PROJECTS For the CITY OF BEAUMONT JEFFERSON COUNTY DRAINAGE DISTRICT NO..6 To assist in the implementation of B,VP A4-1: Reduce adverse water quality impacts of flood control projects undertaken or approved by permittee. Prepared by Carroll & Blackman Inc Beaumont,Texas } , EXHIBIT 16AIP STORM WATER MANAGEMENT TABLE OF CONTENTS NARRATIVE Section Page 1 INTRODUCTION 1 1.1 Background 1.2 BMP A4-1(d) 1.3 Responsibility 1.4 Purpose 2 TYPES OF WATER QUALITY CONTROL STRUCTURES AND USAGE IN THE DESIGN AND PLANNING OF OPEN CHANNEL FLOOD CONTROL PROJECTS 2.1 Sedimentation and Erosion Control Structures 2.1.1 Detention Basins & Ponds 2.1.2 Concrete Revetment 2.1.3 Rip Rap 2.1.4 Concrete Liner 2.1.5 Geotechnical Fabric 2.1.6 Vegetation 2.2 Nutrient Control Structures 2.3 Floatables Control Structures 2.3.1 Siphons 2.3.2 Grates 3 TYPES OF WATER QUALITY CONTROL STRUCTURES AND PRUDENT USAGE IN THE DESIGN AND PLANNING OF STREETS DRAINAGE & FLOOD CONTROL PROJECTS 3.1 Sediment and Erosion Control Structures 3.1.2 Vegetation of Right of Ways 3.2 Floatables and Litter Control Structures 3.2.1 Grated Drop Inlets 4 ASSESSMENT OF POTENTIAL WATER QUALITY IMPACTS RELATED TO FLOOD CONTROL PROJECTS 4.1.1 Open Channels 4.2 Street and Roadways 5 SOUND ENVIRONMENTAL ENGINEERING CERTIFICATION 5.1.1 Engineer's Certification 1.1 BACKGROUND The City of Beaumont (City) and Jefferson County Drainage District No. 6 (District) were issued an NPDES storm water discharge permit (TXS000501) by Region 6 of the U.S. EPA. This permit requires the City and the District to implement various programs referred to as Best Management Practices (BMP's). One such BMP (A4-1) requires the formal adoption of a guidance related to criteria for the incorporation of water quality control structures in new flood control projects and criteria for retrofitting existing flood control projects with water quality control structures. These water quality control structures are intended to improve the water quality of storm water run-off into the municipal separate storm sewer system (MS4). Thus, this guidance is intended to fulfill that requirement as detailed in the NPDES permit BMP A4-1 item d. 1.2 BMP A4-1 (d) BMP A4-1 is included in the Storm Water Management Program of the NPDES Storm Water Permit. This section of the program requires a structured approach for the inclusion of water quality control structures in the design of new flood control projects. The BMP requires in item (d) the following: "Develop guidance materials for incorporation of storm water quality controls into future flood control projects undertaken or approved by applicants." 1.3 RESPONSIBILTY Under the Storm Water Permit, the implementation of the BMP A4-1 is the responsibility of the Jefferson County Drainage District No. 6. 1.4 PURPOSE Storm Water Quality Control Structures that are included in the design of new flood control projects will improve the quality of storm water run-off associated with said projects. These controls will inhibit sedimentation, nutrient loading and prevent major erosion associated with uncontrolled storm water drainage. The primary objective of all flood control projects should be the safety of the citizens of Beaumont. Thus these water quality control structures should be implemented in cases where no sacrifice of public safety will result from control structure inclusion. 2.0 TYPES OF WATER QUALITY CONTROL STRUCTURES AND USES IN OPEN CHANNEL FLOOD CONTROL PROJECTS 2.1 Sedimentation And Erosion Control Structures The following section relates to the control of erosion through the use of storm water quality control structures. These structures include the follow: • Detention Basins & Ponds • Concrete Revetment • Rip Rap • Concrete Liner • Vegetation • Geotechnical Fabric The basis and criteria for the use of these control structures are explained in each subsection. 2.1.1 Detention Basins & Ponds Detention Basins or Ponds are useful in flood control projects where reduced flow velocity is required for a variety of reasons. When large drainage areas with rapid runoff drain through populated areas, detention basins reduce the risk of flooding by serving as a buffering reservoir. The primary use for detention basins and ponds are flood control. Generally these control structures offer a location for storm water to slow and allow for sediments to fall out and collect. Criteria for the selection of Detention Basins & Ponds ♦ Available undeveloped land ♦ Location within the watershed which is conducive to flood protection ♦ Impacts on the flood hydrograph 2.1.2 Concrete Revetment Systems Concrete Revetment systems offer structural support to channel banks. These devices serve as effective erosion controls. Most concrete revetment systems are interlocking concrete blocks designed to have steel cable ties to bind the system together. This increases the rigidity of the channel bank and serves to protect the channel bank from serious erosion and bank slope failures. Concrete Revetment is often installed over a geotechnical fabric for support and backfilled with soil and seeded to promote vegetation growth in the joints. Criteria for the selection of Concrete Revetment Systems for erosion control ♦ Slopes which are steeper than 3:1 ♦ Within Significant Channel Bends ♦ At locations of increased turbulence e.g. channel confluence, pipe entrances, invert grade changes and hydraulic jumps ♦ Bridge & Culvert crossings 2.1.3 Rip Rap Rip Rap bank protection is used to prevent erosion but is generally considered not as effective as concrete revetment. Rip Rap is generally considered to be any large crushed rock or concrete fragments. This material is often available after some construction project that involves the demolition of a larger concrete structure. The advantages of Rip Rap are cost related in many cases. Rip Rap bank protection is used in very much the same fashion as concrete revetment. Criteria for the selection of Rip Rap for erosion control ♦ Significant Channel Bends ♦ Locations of increased turbulence e.g. channel confluence, pipe entrances, invert grade changes and hydraulic jumps ♦ Bridge & Culvert crossings 2.1.4 Concrete Liners Concrete Liners offer channel bank protection in cases where right of way available for acquisition does not allow room for more gentle bank slopes. The concrete liners serve to protect the channel bank from erosion and can be applied to banks with a slope of 2:1 or steeper. Concrete liners can also be utilized around bridge crossing and near other structures to prevent erosion and destabilization. Criteria for the selection of Concrete Liners for erosion control ♦ Slopes steeper than 2:1 ♦ Significant Channel Bends ♦ Locations of increased turbulence e.g. channel confluence, pipe entrances, invert grade changes and hydraulic jumps ♦ Bridge & Culvert crossings 2.1.5 Geotechnical Fabric Geotechnical fabric is available in a diversity of styles with differing functionality. Generally it is a woven fabric composed of polyethylene. Geotechnical fabric can be used in conjunction with soil and seeding in areas where gentle slopes occur in mild bends of earthen channels. This fabric serves as a base and foundation for concrete revetment in cases where these systems are being used to prevent erosion of highly dispersive soil types, such as sand or certain clays. Criteria for the selection of Geotechnical Fabric ♦ Mild channel bends ♦ Support under concrete revetment systems ♦ Additional stability for seed beds 2.1.6 Vegetation Vegetation should be established as quickly as possible on all earthen channel and detention basin projects. The spread of vegetation is promoted generally through the broadcasting of seed and fertilizer. In general, indigenous grass and vegetation species which are disease resistant, hardy and offer favorable maintenance characteristics are specified for flood control projects. Criteria for the selection of Vegetation for erosion control ♦ Exposed earthen surfaces 2.2 Nutrient Control Structures The following section relates to the control of nutrients entering the MS4. The structures include the following: • Grassy Swales • Small Wetlands These structures are effective only if sufficient contact time is allowed and grasses of sufficient density are utilized to uptake nutrients as storm water passes through them. Since flood control projects generally deal with rapid run-off these control structures and the significance of nutrient reduction are as of yet undetermined. Grassy swales are used in conjuction with open channels to direct water to downspout systems constructed of metal or plastic pipe structures. These grassy swales are positioned along the open channels outside 10 to 25 foot grassy right of ways to form a vegetative corridor to prevent sheet flow over the channel banks. Criteria for the selection of Grassy Swales for nutrient control ♦ Available right-of-way outside the flood control structure Criteria for the selection of Small Wetland areas for nutrient control ♦ Presence of wetland protection requirements 2.3 Floatables Control Structures The following section relates to the control of floatables entering the MS4. The structures include the following: • Siphons • Grates These structures are effective as mechanical structures for the removal of low density objects such as litter and floating vegetation. 2.3.1 Siphons Siphons are generally constructed only when a drainage channel meets and intersects a large object that is fixed and significantly inhibits the direct path of the channel. Siphons are created when drainage water is directed under these objects through a conduit which is installed below the channel invert elevation. Siphons can be useful in the reduction of floatable materials and sediment. The effectiveness of these structures are highly related to maintenance activities and the frequency at which floatable materials and sediments are removed. Criteria for the selection of Siphons ♦ Where flood project design requires siphons 2.3.2 Grates Metal gratings can be used to prevent large floatable material from entering the MS4. These structures should be maintained at some schedule determined to be effective for the removal of litter and other large floatable materials. Criteria for the selection of Grates ♦ Where flood control project design requires grates 3.0 TYPES OF WATER QUALITY CONTROL STRUCTURES AND USAGE IN THE DESIGN AND PLANNING OF STREETS & ROADWAY FLOOD CONTROL PROJECTS 3.1 Sediment and Erosion Control Structures 3.1.2 Vegetation of Right-of-Ways All right of ways not paved with concrete should be vegetated as quickly as possible with grasses to prevent erosion and sediment deposition into the storm sewer system. Broadcast or hydromulch seeding or block sodding is required on all flood control projects within the Beaumont Municipal Limits. 3.2 Floatables and Litter Control Structures The use of grates over Drop Inlets can be effective in reducing floatable material and litter introduction into the storm sewer system. The regular cleaning of these structures is necessary for effectiveness. 3.2.1 Grated Drop Inlets Grates are usually thought of in terms of safety issues for the prevention of falls into the storm sewer system. These grates also prevent large floatable materials and litter from entering the MS4. Drop inlets with surface flush mounted inlets are required to have some form of grate to secure the inlet in the Beaumont Municipal Limits. 4.0 ASSESSMENT OF POTENTIAL WATER QUALITY IMPACTS RELATED TO FLOOD CONTROL PROJECTS 4.1 Open Channels All of the water quality control structures included in Section 2.0 should be considered by the engineer at the planning and design stage for all open channel structures. The potential water quality impacts related to open drainage channels are outlined below. Erosion and Sedimentation Problems arise from the following conditions ♦ Drainage Channels with banks that have a slope of steeper than 3:1 ♦ Drainage Channels with highly dispersive soils ♦ Drainage Channels that serve as drainage of large areas with dispersive soils ♦ Drainage Channel bends ♦ Drainage Channel Areas near bridges and other crossing structures All flood control projects should include the use of vegetation in the absence of concrete coverage of any soil surface. 4.2 Street and Roadways Vegetation should be promoted on all right of ways associated with streets in the Beaumont Municipal Limits. 5.0 SOUND ENVIRONMENTAL ENGINEERING CERTIFICATION 5.1.1 Engineer's Certification The engineer shall sign and certify for all new flood control projects that sound environmental engineering was implemented in regards to water quality control. The standardized certification form is included as Appendix B-1. Appendix B-1: Sound Environmental Engineering Certification Certification Of Sound Engineering Practices Related to Water Quality Control Structures for Flood Control Projects City of Beaumont, Texas This document shall serve as certification of sound engineering practices related to the below mentioned flood control project. The undersigned Designing Engineer has read and implemented to the fullest extend practicable some or all of the water quality control structures as describes in the guidance document entitled "Guidelines for the Inclusion of Water Quality Control Structures and the Assessment of Potential Water Quality Impacts in Flood Control Projects". Flood Control Project Name: Project Description: Project General Location: Designing Engineer(s): (Please Print Name and Address) Certification Signature and Date: Engineer Signature: Date: Engineer Registration Number: This document should be included as part of the application for construction permit for all flood control projects located within the Municipal City Limits of Beaumont, Texas.