RFI - Attachment F - Engineering Report

3.1 LABORATORY TESTING METHODOLOGY

The laboratory setup consisting of a rectangular channel, wooden apron, hopper, and catchpit containing t
CFS is shown schematically in Figure 2. The laboratory catchpit was constructed of plexiglas to dimensio
similar to units in the field (catchpit dimensions are presented in Figure 3). The catchpit received water from
skewed apron (sloped in the longitudinal and transverse directions at 10° and 6°, respectively, to the horizon!
plane) so that flow occurred primarily along the lower edge of the wooden apron.

The test procedure involved feeding synthetic road sediment, derived by adding specified amounts of siz
sediments to running water, to the catchpit at various flow rates. Tests were performed for five flow rates (C
Vs, 1 Vs, 4 Is, 12 Vs, 20 Is), four sediment concentrations (50 mg/l, 150 mg/l, 250 mg/A, 400 mg/l) and fc
particle sizes (<100 ft, 100-500 1, 500-1000 pL, 1000-10000 2), yielding a total of 80 tests for each of t
following three cases:

e Catchpit without a CFS (base case)

*® Catchpit with an Enviropod CFS

e@ = Catchpit with a Flogard CFS.
Constant inflows of synthetic runoff to the CFS were maintained for a minimum of four hydraulic retenti
times, corresponding to approximately six minutes for 20 l/s and 30 minutes for 0.5 i/s. The overall C
performance was based on the efficiency of sediment capture under specified flow rates, particle sizes, a
sediment concentrations.
In addition, each of the three cases were tested using street sediments to simulate particle entrapment in-
field. The street sediments were obtained by vacuuming a number of streets in Mt Roskill within the Oak
Creek catchment. The CFS tests with street sediments were conducted for flows of 4 I/s, 12 l/s and 20 l/s, w
an influent sediment concentration of 250 mg/l.
Head loss tests were performed on the filter fabric by passing various flowrates across the filter fabric,

measuring the head on either side of the filter fabric using a peizometer. Figure 1 below shows a schematic
the laboratory set up.

Figure 1: Laboratory Setup for Headloss Measurements

Head Loss

 

 

 

 

  

Filter Fabric