RFI - Attachment F - Engineering Report

2
Technical Papers


                                                               on a predictive            determined to be identical with respect
                                                               probabilistic assessment   to physical characteristics and therefore
                                                               of the sediment load       the media should be considered
                                                               entrained within the       equivalent with respect to expected
                                                               stormwater runoff          solids removal performance.
                                                               from the site. Although
                                                               the cartridges were
                                                                                          Method
                                                               maintained on a yearly     The Mitchell Community College
                                                               basis, a qualitative       RCFS installation was evaluated over
                                                               assessment undertaken      a 20-month period following system
                                                               at the time of the         maintenance in November 2010.
                                                               cartridge exchange did     Independent oversight of all aspects
                                                               not indicate that any      of the project was provided by Ryan
                                                               bypassing of treatment     Winston, MS, Extension Associate
                                                               occurred due to filter     Engineer in the Department of Biological
                                                               occlusion. The yearly      and Agricultural Engineering at North
                                                               maintenance frequency      Carolina State University.
                                                               is unremarkable, given
                                                                                             Sample handling services (sample
                                                               the detention tank
                                                                                          retrieval, system reset and sample
                                                               upstream and the
                                                               RCFS’s passive surface     submittal) were provided by Pace
                                                               cleaning mechanism,        Analytical Services (Pace) and laboratory
                                                               which activates at         work was conducted by Pace and Test
                                                               least once during          America. Precipitation was measured with
Figure 2. Aerial view of the testing site.                     every runoff event         a tipping bucket-type rain gauge. Influent
                                                               and deposits the           and effluent water quality samples
  The RCFS was designed as a capture-                                                     were collected by portable automated
                                             waste on the floor of the cartridge bay.
and-treat system. The storage component                                                   samplers simultaneously collecting flow,
of the system (tank) is a 750mm diameter        The RCFS system contained a total         precipitation and water quality samples.
corrugated metal pipe (CMP) network          of eight, 460mm high, media-filled           Each automatic sampler was connected
designed to capture 75% of the calculated    filter cartridges operating at a flow        to the cellular network for remote
water quality volume (i.e. the runoff        rate of 0.5L/s per cartridge. Each of        communication and data access.
associated with a 25mm event).               the filter cartridges was filled with an
                                             activated alumina media. The media              The influent sampler was equipped
  The treatment component (StormFilter)      used for this study was a granular perlite   with an area velocity flow module with
was designed on a mass-loading basis         coated with activated alumina; this was      low profile sensor for flow analysis
required to meet the annual pollutant        done to aid in the attenuation and/          and influent sample pacing. The effluent
loading requirements of the site with a      or capture of nutrient pollutants by         sampler was equipped with a bubbler
minimum estimated interval between           cation exchange and adsorption. With         flow module used in conjunction with
maintenance of one year. The estimation      the exception of the surface coating,        a weir for flow analysis and effluent
of the yearly maintenance was based          coated and uncoated perlite media were       sample pacing. Sample strainers and flow




water SEPTEMBER 2014