Volume 2-05, Chapter 3 - City of Wichita

Volume 2-05, Chapter 3 - City of Wichita Volume 2-05, Chapter 3 - City of Wichita

11.01.2015 Views

Section 3.3.4 - Underground Sand Filter Figure 3-48 Perimeter Sand Filter Volumes (Source: Claytor and Schueler, 1996) Figure 3-49 Typical Sand Filter Media Cross Sections (Source: Claytor and Schueler, 1996) Page 3 - 168 Volume 2, Technical Guidance

Section 3.3.4 - Underground Sand Filter D. Outlet Structures • An outlet pipe shall be provided from the underdrain system to the facility discharge. Due to the slow rate of filtration, outlet protection is generally unnecessary (except for emergency overflows and spillways). However, the design shall ensure that the discharges from the underdrain system occur in a non-erosive manner. E. Emergency Spillway • An emergency bypass spillway or weir must be included in the underground sand filter design to safely pass flows that exceed the WQv (and CPv if the filter is utilized for channel protection purposes). F. Maintenance Access • The local jurisdiction may require that the facility be placed in a reserve and/or establishment of a drainage easement the facility, which is accessible from a public road or other accessible easement. When required, the drainage easement should be at least 20 feet wide, provide a minimum traversable width of 15 feet, have a maximum slope of no more than 10%, and be appropriately stabilized to withstand maintenance equipment and vehicles. Adequate access must be provided to the grates of the filter bed. Facility designs must enable maintenance personnel to easily remove and replace upper layers of the filter media. G. Safety Features • Inlets, access grates and outlets shall be designed and maintained so as not to permit access by children. Inlet and access grates to the underground sand filters may be locked. 3.3.4.6 Design Procedures Step 1 Step 2 Compute runoff control volumes Calculate the WQ v using equation 1-1. Determine if the development site and conditions are appropriate for the use of an underground sand filter. Consider the Application and Site Feasibility Criteria Check with local agencies as appropriate to determine if there are any additional restrictions and/or surface water or watershed requirements that may apply. Step 3 Compute the peak discharge for the WQ v , called Q wq , using equation 4-18. The peak rate of discharge for water quality design storm is needed for sizing of offline diversion structures. (a) Using WQ v , compute CN using equation 4-3. (b) Compute time of concentration (Chapter 4, Section 4). Volume 2, Technical Guidance Page 3 - 169

Section 3.3.4 - Underground Sand Filter<br />

Figure 3-48 Perimeter Sand Filter <strong>Volume</strong>s<br />

(Source: Claytor and Schueler, 1996)<br />

Figure 3-49 Typical Sand Filter Media Cross Sections<br />

(Source: Claytor and Schueler, 1996)<br />

Page 3 - 168<br />

<strong>Volume</strong> 2, Technical Guidance

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