6617 ASSOCIATED BLVD BASE FILE 2018-01-02 MF Import

. � ..�i.. �_ . ,.. �� Design and Operation Basic Operation The Vorechs�`'System is a hydrodynamic separator designed lo enhance gravilalional separalion nf floating and setUing matenals Irom stormwater(lows.Stormwater flows enter the unit tangentially to the gril chamber, which promotes a gentle swirling motion. As polluted water circles wilhin the gri'. chamber, pollutants migrate loward lhe center ot the unit where velocities are lhe;owest.The majority of seltleable solids are lefl behind as slormwaler exils Ihe gnl chamber lhrough lwo apertures on lhe perimeter of the chamber. Next, buoyanl debris and oil and grease are separa�ed from water tlowing under the baftle wall due to their relalively low specific gravity.As slormwater exils lhe System lhrough the flow conlrol wall and ultimalely through the outlet pipe, it is relatively Iree of floating and setlling pollutants. Over time a conical pile tends lo accumulale in lhe center of the unit conlaining sediment and associated metals, nuirients, hydrocarbons and other pollutanls. Floating debris and oil and grease form a iloating layer trapped in front of the ba�le wall.Accumulalion of these pollutan'.s can easiiy be accessed through manholes over each chamber. Maintenance is typically performed lhrough the manhole over Ihe grit chamber. Design Process Each Vortechs Syslem is custom designed based on: • Sile size • Site runof(coefGcient • Regional precipila�ion intensity distribution • Anticipated pollutant characlerislics These factors are incorporaled into ihe Rational Rainfall MethodT'" to estima�e net annual pollutant removal ef(iciency. The Rallona/Raln/all MethodT" Uifferences in local climate,topography and sr,ale make every sile hydraulically unique. Il is importanl lo take these fac�ors into consideralion when eslimaling the long-term peAortnance o(any stormwater treatment syslem. The Rational Rainfall Method"" combines site-specifc information wilh laboratory generated perTormance data, and local historical precipitalion records to estimale efficiencies as accuralely as possible. Short duration rain gauge records from across the United States and Canada were analyzed to determine lhe percenl of lhe lotal annual rainfall that fell at a range of inlensities. US stalions'deplhs were .otaled every 15 minutes or houriy and recorded in 0.01•inch increments. Depths were recorded hourly with 1 mm resolulion a�Canadian slations. One Uend was consistent at all sites; Ihe vast majonty of precipitalion lell at low intensities and high intensity storms conlributed relatively litqe lo lhe total annual depih. These intensilies, along with ihe tolal drainage area and runofi coefficient tor each specific site, are translated irdo Oow rales using the Rational Rainfall Method. Since most sites are relatively small and hiyhly impervious, ihe Rational Rainfall Melhod is appropriate. Based on the flow rates calculated for each intensity, an operating rate within a proposed VoAechs Syslem is determined. Flnally,a removal elfciency is selecled (or each operaling rale based on anticipated pollulant r,harec�enstics and on tull scale laboratory tests. The relative removal eff,ciency al each operaling rale is added to produce a nel annual pollutant removal effciency estimate. CONTECH Stormwater Solulions typically selects the system that will provide an 80%annual TSS load reduction based on labora�ory generaled periormance curves for 50-micron sediment particles, t 14 02005 CONTECH Stormwater Solutions