complete drainage report rev 9

7. Sizing Requirement: The example below demonstrates the sizing procedure for the Filterra® HC: Example: A 0.25-acre impervious site is to be treated to 80% TSS removal using the Filterra® HC. The impervious site runoff (Q) based on the New Jersey Water Quality Design Storm was determined to be 0.79 cfs. The selection of the appropriate model of Filterra® HC is based upon both the maximum inflow drainage area and the MTFR. It is necessary to calculate the required model using both methods and to use the largest model determined by the two methods. Inflow Drainage Area Evaluation: The drainage area to the Filterra® HC in this example is 0.25 acres. Included in Table 1 below, all of the Filterra® HC models are designed with a maximum allowable drainage area greater than 0.25 acres. Specifically, the Filterra® HC with a 4’x4’ media bay and a maximum allowable drainage area of 0.40 acres would be the smallest model able to treat runoff without exceeding the maximum allowable drainage area. Maximum Treatment Flow Rate (MTFR) Evaluation: The site runoff (Q) was based on the following: time of concentration = 10 minutes i= 3.2 in/hr (page 5-8, Fig. 5-3 of the NJ Stormwater BMP Manual) c = 0.99 (runoff coefficient for impervious) Q=ciA = 0.99 x 3.2 x 0.25 = 0.79 cfs Given the site runoff is 0.79 cfs and based on the MTFR’s listed in Table 1 below, the Filterra®” HC with a 16’x8’ media bay and an MTFR of 0.889 cfs would be the smallest model that could be used to treat the impervious area without exceeding the MTFR. If using more than one unit for treating runoff, the units should be configured such that the flowrate to each unit does not exceed the design MTFR for each unit and ensuring the entire 0.25 acre area is treated. The MTFR evaluation results will be used since that method results in the highest minimum configuration determined by the two methods.