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From page 86... ... 86 C H A P T E R 5 This chapter provides guidance for incorporating VRAs into the urban highway environment, including identifying potentially suitable VRAs, prioritizing VRAs based on a number of factors, and developing conceptual designs to incorporate these VRAs into the overall project design. This chapter provides guidance for assimilating the site and project information available for the site (Section 3.4) Read the entire page →
From page 87... ... Selecting and Applying Volume Reduction Approaches 87 5.1.2 Overview of Framework The overall framework for volume reduction planning described in this manual is based on assimilating a number of factors, including (1) project goals, (2) Read the entire page →
From page 88... ... 88 Volume Reduction of Highway Runoff in Urban Areas feasibility and desirability analyses and quantifying relative capital cost, operational expense, and performance. In general, the process of developing a volume reduction plan can be considered in three phases: 1. Read the entire page →
From page 89... ... Selecting and Applying Volume Reduction Approaches 89 5.2 Initial Screening to Identify Potential VRAs (Step 3) Chapter 4 describes a relatively broad menu of potential VRAs and the locations within an urban highway project where these approaches could be located. Read the entire page →
From page 90... ... 90 Volume Reduction of Highway Runoff in Urban Areas 5.2.1 Step 3a -- Develop Site Layout and Geometric Design The primary inputs to this step are the geometric constraints and the transportation and safety objectives that are inherent to the project. This step should be informed by the volume reduction site planning principles described in Section 4.2.3. Read the entire page →
From page 91... ... Selecting and Applying Volume Reduction Approaches 91 • Section 4.3 provides a summary of applicability of the menu of VRAs for general locations (i.e., medians, shoulders) within the highway environment. Read the entire page →
From page 92... ... 92 Volume Reduction of Highway Runoff in Urban Areas Table 25. Checklist of site applicability. Read the entire page →
From page 93... ... Selecting and Applying Volume Reduction Approaches 93 Table 25. (Continued) Read the entire page →
From page 94... ... 94 Volume Reduction of Highway Runoff in Urban Areas This manual provides the following resources to support this step: • Section 3.4 describes site assessment activities intended to characterize the site and watershed conditions relative to volume reduction design, including: – Phasing of site assessment activities -- Section 3.4.1, – Topography and drainage patterns -- Section 3.4.2, – Off-site drainage and adjacent land uses -- Section 3.4.3, – Soil and geologic conditions -- Section 3.4.4, – Local weather patterns -- Section 3.4.5, – Groundwater considerations -- Section 3.4.6, – Geotechnical considerations -- Section 3.4.7, – Existing utilities -- Section 3.4.8, – Harvested-water–demand assessment -- Section 3.4.9, – Responsible agencies and other stakeholders -- Section 3.4.10, – Local ordinances -- Section 3.4.11, and – Watershed-based and other joint planning opportunities -- Section 3.4.12. Part 3: Other Project-Specific Factors Instructions: 1. Read the entire page →
From page 95... ... Selecting and Applying Volume Reduction Approaches 95 • Chapter 4 and Appendix A describe the menu of VRAs and provide a summary of considerations related to specific VRAs: – Section 4.3.1 describes volume reduction processes associated with each VRA and the relative risk of water balance. – Section 4.3.3 provides a summary of potential geotechnical impacts associated with infiltration by VRA. Read the entire page →
From page 96... ... 96 Volume Reduction of Highway Runoff in Urban Areas a systematic process of evaluating infiltration feasibility and desirability is provided in this section, and it is recommended that this screening be done prior to screening other volume reduction mechanisms. Read the entire page →
From page 97... ... Selecting and Applying Volume Reduction Approaches 97 Infiltration Infeasibility Screening The primary questions that are evaluated as part of infiltration infeasible screening are: • Is infiltration feasible and desirable? • If so, what quantity of infiltration is feasible and desirable? Read the entire page →
From page 98... ... 98 Volume Reduction of Highway Runoff in Urban Areas classification and establish specific design parameters such as infiltration rate and factor of safety. • Category 2 -- Partial Infiltration. Read the entire page →
From page 99... ... Selecting and Applying Volume Reduction Approaches 99 Table 26. (Continued) Read the entire page →
From page 100... ... 100 Volume Reduction of Highway Runoff in Urban Areas for answering the feasibility and desirability screening questions posed in Table 26. References to "lines" in these sections refer to line numbers in Table 26. Read the entire page →
From page 101... ... Selecting and Applying Volume Reduction Approaches 101 Guidance for Screening Geotechnical Considerations (Lines 2 and 6) More detailed guidance for evaluating geotechnical considerations is provided in Section 3.4 and Appendix E Read the entire page →
From page 102... ... 102 Volume Reduction of Highway Runoff in Urban Areas Guidance for Screening Groundwater Quality Considerations (Lines 3 and 7) Guidance for evaluating groundwater quality considerations is provided in Section 3.4 and Appendix D Read the entire page →
From page 103... ... Selecting and Applying Volume Reduction Approaches 103 VRA Selection and Design Considerations to Maximize ET Losses Where vegetated BMPs are used, and where it is not feasible or desirable to meet full project goals with infiltration (i.e., Category 2 or 3 infiltration screening conditions) , ET losses can contribute toward meeting project goals. Read the entire page →
From page 104... ... 104 Volume Reduction of Highway Runoff in Urban Areas Key Differences in Demand Calculations for Harvest-and-Use Feasibility Versus Water Supply Planning It is important to note that harvested-water–demand calculations differ in purpose and methods from water demand calculations done for water supply planning. When designing harvest-and-use systems for stormwater management, a reliable method of relatively quickly regenerating storage capacity (i.e., using water) Read the entire page →
From page 105... ... Selecting and Applying Volume Reduction Approaches 105 • Demand calculations should be based on the average rate during the wet season (defined based on local climate patterns) for a typical year. Read the entire page →
From page 106... ... 106 Volume Reduction of Highway Runoff in Urban Areas Assimilate Screening Results to Identify Potentially Suitable VRAs Based on the results from the previous subsections, the user can develop a refined understanding of the role that each volume reduction process can be expected to serve in reducing runoff volumes. This can in turn guide the selection of VRAs that are compatible with the feasibility and desirability screening conditions that are identified. Read the entire page →
From page 107... ... Selecting and Applying Volume Reduction Approaches 107 5.2.4 Combined Results of Initial Screening Processes Based on the analysis of applicability described in Section 5.2.2 and the screening of feasibility and desirability described in Section 5.2.3, the user can create a narrowed list of potentially suitable VRAs for further consideration. Using Table 31 as a checklist of potential VRAs, the applicability results summarized in Table 25 can be used to narrow down the potential VRAs within each screening category to only those that are potentially applicable to the site. Read the entire page →
From page 108... ... 108 Volume Reduction of Highway Runoff in Urban Areas outlines an approach for prioritizing from the screened list of VRAs. It is intended to help the user answer the following questions: • How do considerations such as performance, reliability, cost, O&M, and project types (i.e., new roadway vs. Read the entire page →
From page 109... ... Selecting and Applying Volume Reduction Approaches 109 • Planning for the VRA feature in rough grading plans can help result in a net balance of cut and fill for the VRA such that excavation or hauling costs would not be incidental to the VRA construction, and • Planning for VRAs may require more extensive investigation and analysis than for traditional roadway design. For retrofit projects, what is the net cost of implementing the VRA considering the modifications that would be needed to existing infrastructure? Read the entire page →
From page 110... ... 110 Volume Reduction of Highway Runoff in Urban Areas • Prioritizing VRAs that are currently in use and the agency has experience operating and maintaining. • Introducing promising VRAs as pilot projects initially before using them on a broad scale. Read the entire page →
From page 111... ... Selecting and Applying Volume Reduction Approaches 111 Relative Performance in Comparison to Volume Reduction Goals (i.e., effectiveness) Performance of VRAs is a function of many site-specific factors. Read the entire page →
From page 112... ... 112 Volume Reduction of Highway Runoff in Urban Areas • What sizing of a given volume reduction approach is needed to meet my performance benchmarks? • How can modeling tools be used to support conceptual design? Read the entire page →
From page 113... ... Selecting and Applying Volume Reduction Approaches 113 5.4.2 Developing Initial Conceptual Designs Conceptual designs, by definition, do not contain adequate detail for construction but should include the key parameters needed to define how the system is intended to function and interact with other elements of the design. The conceptual design of VRAs should begin with initial site planning by considering the potential locations for VRAs, tributary areas to these VRAs, approximate footprints needed for VRAs, and the general grading requirements of these VRAs. Read the entire page →
From page 114... ... 114 Volume Reduction of Highway Runoff in Urban Areas Figure 29 shows an example of schematic design exhibits contained in the VRA fact sheets. Figure 30 provides examples of a preliminary conceptual site plan for a hypothetical VRA retrofit, illustrating that several options can be efficiently considered as part of a single conceptual design development process. Read the entire page →
From page 115... ... Selecting and Applying Volume Reduction Approaches 115 Sections 5.2 and 5.3 provide guidance for identifying which VRAs may be applicable, feasible, and desirable as well as guidance for considering factors such as maintenance, reliability, cost, and performance in selecting VRAs for detailed consideration. While there are specific numeric criteria associated with these decisions, the overall decisions of which VRAs to evaluate tend to be narrative and qualitative. Read the entire page →
From page 116... ... 116 Volume Reduction of Highway Runoff in Urban Areas • Example 4: Match the long-term volume of surface runoff that is estimated to have occurred in the pre-project condition. • Example 5: Reduction in the frequency of discharge from the site (i.e., reduce the frequency of discharge by 50% compared to baseline conditions without controls) Read the entire page →
From page 117... ... Selecting and Applying Volume Reduction Approaches 117 User's Guide and Tool Download Information Appendix B is a user's guide for the Volume Performance Tool and contains its technical specifications and the underlying theory behind it. Intended Use of the Tool for VRA Selection and Conceptual Design The tool is intended to take the place of a planning-level continuous simulation model and, most simply, it is intended to provide an estimate of long-term VRA performance for a given set of input parameters. Read the entire page →
From page 118... ... 118 Volume Reduction of Highway Runoff in Urban Areas the user can quickly determine how much variability would be expected in performance as a function of project location if a uniform design standard were to be adopted across an entire jurisdiction (for example, a single design-storm depth across a state) Read the entire page →
From page 119... ... Selecting and Applying Volume Reduction Approaches 119 subscription services such as RSMeans (http://rsmeans.reedconstructiondata.com/) , and resources specific to stormwater facilities such as WERF BMP whole life-cycle cost worksheets (Lampe, 2005) Read the entire page →
From page 120... ... 120 Volume Reduction of Highway Runoff in Urban Areas vacuuming (and the equipment necessary to sweep/vacuum) , whereas bioretention areas might require regular upkeep of the vegetation both for performance and for public acceptance. Read the entire page →
From page 121... ... Selecting and Applying Volume Reduction Approaches 121 the nature of the rehabilitation or replacement activities that would be needed for a given VRA. In some cases, rehabilitation or replacement would only cost a portion of the initial costs (e.g., replacing media and plants in a bioretention area without having to pay for piping and overall site improvements) Read the entire page →
From page 122... ... 122 Volume Reduction of Highway Runoff in Urban Areas The total NPV of future effort can be calculated by summing the NPV of each future event: NPV , 10 ∑ ( ) Read the entire page →
From page 123... ... Selecting and Applying Volume Reduction Approaches 123 Where Net WLC is as calculated for the period of evaluation, i is the discount rate as a fraction (0 to 1) , and n is the length of the period of evaluation (years) Read the entire page →
From page 124... ... 124 Volume Reduction of Highway Runoff in Urban Areas rates were marginal, the use of real-time controls could allow the system to be operated either as a VRA (i.e., hold water back to infiltrate slowly) or a treatment BMP depending on the timing until the next storm is anticipated to arrive. Read the entire page →
From page 125... ... Selecting and Applying Volume Reduction Approaches 125 associated with not having local examples of past projects. Carefully planned pilot projects can be costly up front, but can result in long-term savings associated with the agency and contractor experience gained. Read the entire page →
From page 126... ... 126 Volume Reduction of Highway Runoff in Urban Areas General Category Manages Project Runoff? Typical Location of VRA (Inside or Outside ROW) Read the entire page →
From page 127... ... Selecting and Applying Volume Reduction Approaches 127 • Multi-jurisdictional partnerships for developing stormwater retrofit have been established or are of mutual interest to parties in the vicinity of the project. • Watershed-scale resource issues such as groundwater balance issues, salt and nutrient management planning, base-flow augmentation, or groundwater source protection/management are present and would be better addressed via a coordinated watershed-scale approach for evaluating VRA feasibility and siting rather than a site-by-site approach. Read the entire page →

From page 86...

... 86 C H A P T E R 5 This chapter provides guidance for incorporating VRAs into the urban highway environment, including identifying potentially suitable VRAs, prioritizing VRAs based on a number of factors, and developing conceptual designs to incorporate these VRAs into the overall project design. This chapter provides guidance for assimilating the site and project information available for the site (Section 3.4)