Rated for 80% TSS Removal by Metro Nashville Water Services

Transcription

1 This is a regional document for Nashville, TN TN Nashville, TN Stormwater Design Guide Rated for 80% TSS Removal by Metro Nashville Water Services The is a modular, high-rate stormwater filtration technology approved by Metro Nashville Water Services for 80% TSS removal. The modules are house in vaults (Table 1) and manholes (Table 2) with size and layout depending on site specific criteria. Metro Nashville Approved Sizing Methodologies Water Quality Flow Rate based on the Metro Nashville Design Storm (2.45 / hr) The has been designed as a modular filtration system. Therefore, it can be sized to treat any flow rate resulting from the 2.45 / hr Nashville Quality Design Storm. Each filter module has a treatment capacity of 25 gpm (0.056 cfs). The quantity of modules comes from the following equation: # Filter = (Q wq x gpm/cfs) / 25gpm Mass Loading for Filters Downstream of Extended Detention The may also be sized based upon the maximum sediment load generated from the site s impervious drainage area when the is downstream of extended detention. For this design, one filter module is required for every 0.66 impervious acre. NOTE: The consulting engineer will want to confirm which sizing method, flow based or mass load, is more conservative for final Up- Flo Filter module count determination. Inline Sizing Inline Vault configurations contain an internal inlet bay, weir wall, and outlet bay, making each vault a stand-alone offline device. Sizing for inline systems is shown in Table 1. Hydro International s design engineers will assist in hydraulic modeling. Table 1. Inline Vault Sizing Approved by Metro Nashville for 80% TSS Removal Approved Nashville Water Quality Treatment Flow Rate Inline Vault Dimensions (cfs) (gpm) (No.) (Length x Width I.D.) x 8 Page 1

2 Table 1 (Cont d from Page 1). Inline Sizing. Approved Nashville Water Quality Treatment Flow Rate Inline Vault Dimensions (cfs) (gpm) (No.) (Length x Width I.D.) x Varies - please inquire Page 2

3 Table 1 (Cont d from Page 2). Inline Sizing. Approved Nashville Water Quality Treatment Flow Rate Inline Vault Dimensions (cfs) (gpm) (No.) (Length x Width I.D.) , , , , , , , , , , , , , , , , , , Varies - please inquire 1 1 Contact Hydro International for layout recommendations when the required Water Quality flow rate is greater than cfs. Layout - Inline and Offline Systems Offline Design Plan View Metro Nashville approves all manufactured filtration systems for offline use only, meaning that the peak design flow must be routed around the filtration chamber. The Inline vault systems in Table 1 incorporate a high-flow channel that directs peak flows around the treatment chamber, meeting Nashville s requirement for offline systems. Hydro International can also provide offline Up-Flo manholes or vaults. Offline designs use external junction manholes instead of incorporating internal high flow channels like the Inline systems (Fig.1). Table 2 shows the common offline manhole specifications. BYPASS MANHOLE UP-FLO FILTER Fig.1 Plan View of an Offline. Page 3

4 Table 2. Offline Manhole Sizing Certified by Metro Nashville for 80% TSS Removal Approved Nashville Water Quality Treatment Flow Rate Manhole Dimensions (cfs) (gpm) (No.) (I.D.) Round (Offline only) NOTE: For flows greater than cfs, use an Inline Vault from Table 1. Offline Design Profile View It is recommended for the consulting engineer to provide 9.5 of drop between the manhole inlet and outlet pipes. The weir height in the external bypass manhole should then be set 29.5 above the invert of the outlet pipe. This provides approximately 30 of driving head from the top of the external weir in the bypass manhole, to the invert of the outlet pipe of the Up- Flo Filter. This concept is displayed in Figure 2 below. In the case that 30 of driving head is not available due to site restrictions the consulting engineer should contact the Tennesee Hydro International representative at (770) RIM EL. 8.0 ft. 96 in [8.0 ft] WEIR EL ft in [5.46 ft] TOP OF SLAB EL ft in [7.21 ft] INLET EL ft in [3.79 ft] Fig.2 Typical Section of the Drainage Profile. OUTLET & TOP OF SUPPORT EL. 3.0 ft. 36 in [3.0 ft] SUMP EL. 0.0 ft. 0 in [0.0 ft] Page 4

5 Sizing Calculator for Tennessee Projects It is recommended that consulting engineers evaluating the for use on a Tennessee project use Hydro International s Excel-based Sizing Calculator. Using basic project-specific inputs such as Water Quality Flow Rate, the tool calculates the number of required (Fig.3). It uses the Metro Nashville-approved flow rate of 25 gpm per Filter Module to calculate the number of Filter required for a Nashville project. The calculator can also be used to generate site-specific detail drawings if the user opts to input additional project-specific information such as pipe size, pipe inverts and finished grade elevations. Users may opt to submit their design to Hydro International for a technical review and pricing. To download the Sizing Calculator visit Fig.3 The Sizing Calculator uses the Metro Nashville-approved flow rate of 25 gpm per Filter Module to calculate the number of Filter required for a Nashville project. Important Links Interactive Sizing Calculator: at Hydro International Homepage: Nashville, TN Metro Water Services Approval Letter: Stormwater-Management-Manual/Regulations.aspx Page Hydro International UF_DG_Nashville_F/1504

6 Nashville, TN Design Worksheet Instructions Complete the Design Worksheet with your project submission to Nashville Metro Water Services. Include detail drawings of the selected Model with the worksheet. Site Information Project / Site Name: Site Address: Total Contributing Drainage Area: Total Contributing Impervious Drainage Area: Runoff Coefficient: Design Data Module Flow Rate* : (gpm/filter Module) *maximum allowable = 25 gpm or cfs per Filter Module) Water Quality Treatment Flow Rate Required (cfs) Calculations Show or attach sizing for flow rate and maximum impervious area. Selected Model (e.g. 4-ft Manhole Up-Flo Filter with 5 Filter ): Bypass Flow Rate: Bypass Configuration: Other relevant information specific to this : Tennessee Representative - Will Hall; (770) ; whall@hydro-int.com Hydro International, 94 Hutchins Drive, Portland, ME Tel: (207) Fax: (207) Page 6 stormwaterinquiry@hydro-int.com Web: Hydro International UF_DG_Nashville_F/1504