MCU16/0012 Attach B Engineering report & SMP

1.1     DESCRIPTION

StormFilter is a passive, flow-through stormwater filtration system. It consists of vaults that house
rechargeable cartridges filled with a variety of filter media. The filter systems are installed in-line with storm
drains. The StormFilter works by passing stormwater through media-filled cartridges, which trap particulates
and adsorb materials such as dissolved metals and hydrocarbons. After being filtered through the media, the
treated stormwater flows into a collection pipe or discharges into an open channel drainage way. StormFilter
is offered in three different configurations: cast-in-place, precast and linear. The precast and linear models
utilize pre-manufactured vaults. The cast-in-place units are customized for larger flows and may be either
covered or uncovered underground units.


1.2     OPERATION

1.2.1   Purpose

The StormFilter is a passive stormwater filtration system designed to improve the quality of stormwater runoff
from the urban environment before it enters receiving waterways.

Through independent third party studies, it has been demonstrated that the StormFilter is highly effective for
treatment of first flush flows and flow-paced flows during the latter part of a storm. In general, StormFilter's
efficiency is highest when pollutant concentrations are highest. The primary target pollutants for removal are:
sediments (TSS), soluble metals, soluble phosphorus, nitrates, and oil and grease.


1.2.2   Sizing

The StormFilter is typically sized to treat the peak flow of a water quality design storm as it passes through
the filter. The peak flow is determined by calculations based on the contributing watershed hydrology and
using a design storm magnitude. The design storm is usually based on the regulatory requirements set by the
local stormwater management agency. The particular size of a StormFilter is determined by the number of
filter cartridges (see Figure 4) required to treat the peak stormwater flow. Each cartridge is designed to treat a
peak flow of 1 Litre/second. For example: a peak design stormwater flow rate of 10L/s would require that 10
cartridges be used in the treatment vault.

Because of the highly porous nature of the granular filter media, the flow through a newly installed cartridge is
restricted to 1L/s, using a restrictor disc, to ensure adequate pollutant-media contact time.


1.2.3   Basic Function

The StormFilter is designed to siphon stormwater runoff through a filter cartridge containing media. The
variety of media available can be designed to act as a mechanical filter to remove sediments, as an ion
exchanger to remove dissolved heavy metals, and as an absorber to remove oils and greases.




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