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HomeMy Public PortalAboutHDSU - Vortsentry VS Maintenance Guide-: �iOrili i CA F! STORMWATER SOLUTIONS.. VortSentry® Guide Operation, Design, Performance and Maintenance VortSentry® The VortSentry is a hydrodynamic separator with a small footprint. The internal bypass ensures treatment chamber velocities remain low, which improves performance and eliminates the risk of re -suspension. In addition to standalone applications, the VortSentry is an ideal pretreatment device. The system is housed inside a lightweight concrete manhole structure for easy installation (often without the use of a crane) and unobstructed maintenance access. Operation Overview Stormwater runoff enters the unit tangentially to promote a gentle swirling motion in the treatment chamber. As polluted water circles within the chamber, settleable solids fall into the sump and are retained. Buoyant debris and oil rise to the surface and are separated from the water as it flows under the baffle wall. Finally, treated water exits the treatment chamber through a flow control orifice located behind the baffle wall. During low -flow conditions all runoff is diverted into the treatment chamber by the flow partition through the inlet aperture. At higher flow rates, a portion of the runoff spills over the flow partition and is diverted around the treatment chamber to prevent re -suspension and washout of previously trapped pollutants. Water that spills over the partition flows into the head equalization chamber above the treatment chamber outlet. As the head equalization chamber fills, the head differential driving flow through the treatment chamber collapses. The result is that flow rates in the treatment chamber remain relatively constant even as total flow rates increase substantially. This configuration further reduces the potential for re -suspension or washout. INLET APERTURE INLET PIPE TREATMENT CHAMBER BAFFLE TREATMENT CHAMBER 2 FLOW PARTION OUTLET PIPE HEAD EQUALIZING BAFFLE OUTLET FLOW CONTROL ORIFICE SEDIMENT STORAGE SUMP Design Basics There are two primary methods of sizing a VortSentry system. The Water Quality Flow Rate Method determines which model size provides the desired removal efficiency at a given flow for a defined particle size. The Rational Rainfall Method'" is used when a specific removal efficiency of the net annual sediment load is required. Typically, VortSentry systems are designed to achieve an 80% annual solids load reduction based on lab generated performance curves for a gradation with an average particle size (d50) of 110-microns (pm). Water Quality Flow Rate Method In many cases, regulations require that a specific flow rate, often referred to as the water quality design flow (WQQ), be treated. This WQQ represents the peak flow rate from either an event with a specific recurrence interval (i.e. the six-month storm) or a water quality depth (i.e. 1/2-inch of rainfall). The VortSentry is designed to treat all flows up to the WQQ, due to its partition design in the treatment chamber, flow rates only increase minimally once the WQQ is surpassed. At influent rates higher than the WQQ, the flow partition will direct most flow exceeding the treatment flow rate around the treatment chamber. This allows removal efficiency to remain relatively constant in the treatment chamber and reduces the risk of washout during bypass flows regardless of influent flow rates. Treatment flow rates are defined as the rate at which the VortSentry will remove a specific gradation of sediment at a specific removal efficiency. Therefore they are variable based on the gradation and removal efficiency specified by the design engineer. Rational Rainfall Method'" Differences in local climate, topography and scale make every site hydraulically unique. The Rational Rainfall Method is a sizing program CONTECH developed to estimate a net annual sediment load reduction for a particular VortSentry model based on site size, site runoff coefficient, regional rainfall intensity distribution, and anticipated pollutant characteristics. For more information on using the summation of the Rational Rainfall Method, see Vortechs Technical Bulletin 4: Modeling Long Term Load Reduction: The Rational Rainfall Method, available at www.contechstormwater. com. Treatment Flow Rate The outlet flow control orifice is sized to ensure that the WQQ passes through the treatment chamber at a water surface elevation equal to the crest of the flow partition. The head equalizing baffle applies head on the outlet flow control to limit the flow through the treatment chamber when bypass occurs, thus helping to prevent re -suspension or re -entrainment of previously captured particles. Hydraulic Capacity VortSentry hydraulic capacity is determined by the length and height of the flow partition and by the maximum allowable head in the system. Typical configurations allow hydraulic capacities of up to four times the treatment flow rate. As needed, the crest of the flow partition may be lowered and the flow partition area may be widened to increase the capacity of the system at a given water surface elevation. The unit is designed to meet project specific hydraulics. Performance Full -Scale Laboratory Test Results Laboratory testing of the VortSentry was conducted using OK- 110, a commercially available pure silica product with an average particle size of 110-pm (Table 1). This material was metered into a four -foot diameter VortSentry model VS40 at an average concentration of 110-mg/Ls at flow rates ranging from 0.20-cfs to 2.0-cfs (5.7-L/s to 57-L/s). US Standard Sieve Size Particle Size Cumulative Micron pm Passing % 70 100 120 140 170 200 Table 1 : US Silica OK-110 212 150 125 106 88 75 Particle Size Distribution 99.8% 98.8% 83.8% 43.0% 18.0% 3.0% Removal efficiencies at each flow rate were calculated based on net sediment loads passing the influent and effluent sample points. Results are illustrated in Figure 1. Removal Efficiency 0.5 (14) 1.D (25) 0 cfs ltls) Figure 1: VS40 Removal Efficiencies for US Silica OK-110 Particle Size Distribution 1.6 (42) 2.0 (57) Assuming that sediment in the inlet chamber is ideally mixed, removal rates through the system will decay according to the percentage of flow bypassed. This effect has been observed in the laboratory where the test system is designed to produce a thoroughly mixed inlet stream. All VortSentry models have the same aspect ratio regardless of system diameter (i.e. an increase in diameter results in a corresponding increase in depth). Operating rates are expressed volumetrically. The removal efficiency at each operating rate is calculated according to the average of volumetric and Froude scaling methods and is described by Equation 1. Equation 1 and actual laboratory test results were used to determine the flow rate which would be required for the various VortSentry models to remove 80% of solids. Diameter Prototype )2 75 = \ Flow Rate Prototype Equation 1: Diameter Model Flow Rate Model View full report at www.contechstormwater.com Maintenance The VortSentry system should be inspected at regular intervals and maintained when necessary to ensure optimum performance. The rate at which the system collects pollutants will depend more heavily on site activities than the size of the unit, i.e., unstable soils or heavy winter sanding will cause the treatment chamber to fill more quickly but regular sweeping will slow accumulation. Inspection Inspection is the key to effective maintenance and is easily performed. Pollutant deposition and transport may vary from year to year and regular inspections will help ensure that the system is cleaned out at the appropriate time. At a minimum, inspections should be performed twice per year (i.e. spring and fall) however more frequent inspections may be necessary in equipment washdown areas and in climates where winter sanding operations may lead to rapid accumulations. It is useful and often required as part of a permit to keep a record of each inspection. A simple inspection and maintenance form for doing so is available at www.contechstormwater.com. The VortSentry should be cleaned when the sediment has accumulated to a depth of three feet in the treatment chamber. This determination can be made by taking two measurements with a stadia rod or similar measuring device; one measurement from the manhole opening to the top of the sediment pile and the other from the manhole opening to the water surface. If the difference between these measurements is less than the distance given in Table 2, the VortSentry should be maintained to ensure effective treatment. Cleaning Cleaning of the VortSentry should be done during dry weather conditions when no flow is entering the system. Cleanout of the VortSentry with a vacuum truck is generally the most effective and convenient method of excavating pollutants from the system. Simply remove the manhole cover and insert the vacuum hose into the sump. All pollutants can be removed from this one access point from the surface with no requirements for Confined Space Entry. In installations where the risk of petroleum spills is small, liquid contaminants may not accumulate as quickly as sediment. However, an oil or gasoline spill should be cleaned out immediately. Motor oil and other hydrocarbons that accumulate on a more routine basis should be removed when an appreciable layer has been captured. To remove these pollutants, it may be preferable to use adsorbent pads, which solidify the oils. These. are usually much easier to remove from the unit individually, and less expensive to dispose than the oil/water emulsion that may be created by vacuuming the oily layer. Floating trash can be netted out if you wish to separate it from the other pollutants. Manhole covers should be securely seated following cleaning activities to prevent leakage of runoff into the system from above and also to ensure proper safety precautions. If anyone physically enters the unit, Confined Space Entry procedures need to be followed. Disposal of all material removed from the VortSentry should be done is accordance with local regulations. In many locations, disposal of evacuated sediments may be handled in the same manner as disposal of sediments removed from catch basins or 3 deep sump manholes. Check your local regulations for specific requirements on disposal. VortSentry Model Diameter Distance from Water Surface to Top of Sediment Pile Sediment Storage Capacity VS30 VS40 VS50 VS60 VS70 VS80 ft 3 4 5 6 7 8 m 0.9 1.2 1.5 1.8 2.1 2.4 ft 2.5 3.7 4.5 5.5 6.4 7.2 m 0.8 1.1 1.4 1.6 2.0 2.2 Table 2: VortSentry Maintenance Indicators and Sediment Storage Capacities. Logon to www.contechstormwater.com to download the VortSentry Inspection and Maintenance Log. For assistance with maintaining your VortSentry, contact us regarding the CONTECH Maintenance Compliance Certification Program. yd3 0.8 1.4 2.2 3.1 4.3 5.6 m3 0.6 1.1 1.7 2.4 3.3 4,3 Note: To avoid underestimating the volume of sediment in the chamber, carefully lower the measuring device to the top of the sediment pile. Finer silty particles at the top of the pile may be more difficult to feel with a measuring stick. These finer particles typically offer less resistance to the end of the rod than larger particles toward the bottom of the pile. Support • Drawings and specifications are available at www.contechstormwater.com. • Site -specific design support is available from our engineers. ©2008 CONTECH Stormwater Solutions CO"Mov F S'1ORMWATER OWTIONS_ 800.925,5240 contechstormwater.com CONTECH Construction Products Inc. provides site solutions for the civil engineering industry. CONTECH's portfolio includes bridges, drainage, sanitary sewer, stormwater and earth stabilization products. For information on other CONTECH division offerings, visit contech-cpi.com or call 800.338.1122 Nothing in this catalog should be construed as an expressed warranty or an implied warranty of merchantability or fitness for any particular purpose. See the CONTECH standard quotation or acknowledgement for applicable warranties and other terms and conditions of sale. The product(s) described may be protected by one or more of the following US patents: 5,322,629; 5,624,576; 5,707,527; 5,759,415; 5,788,848; 5,985,157; 6,027,639; 6,350,374; 6 406,218; 8,641,720; 6,511,595; 6,649,048; 6,991,114; 6,998,038, 7,186,058; 7,296,692; 7,297,266; related foreign patents or other patents pending. vs_manual-1 06/08 ORECYCLED PAPER VortSentry Inspection & Maintenance Log VortSentry Model: Location: Date Water depth to sediment' Floatable Layer Thickness' Describe Maintenance Performed Maintenance Personnel Comments 1 . The water depth to sediment is determined by taking two measurements with a stadia rod: one measurement from the manhole opening to the top of the sediment pile and the other from the manhole opening to the water surface. If the difference between these measurements is less than the distance given in Table 1, the system should be cleaned out. Note: To avoid underestimating the volume of sediment in the chamber, the measuring device must be carefully lowered to the top of the sediment pile. 2. For optimum performance, the system should be cleaned out when the floating hydrocarbon layer accumulates to an appreciable thickness. In the event of an oil spill, the system should be cleaned immediately.