What is the required Total Suspended Solids (TSS) removal rate for redeveloped areas?
Redevelopment, defined for the purposes of this question, is a new impervious surface that replaces an equal area of existing impervious surface on a project site. For redevelopment of existing impervious surfaces, the required TSS removal rate is the greater of the TSS removal rate of the existing stormwater treatment system, or 50% TSS is required. For new impervious surfaces an 80% TSS removal rate applies. However, the water quality provisions of the Stormwater Management rules only apply if the impervious surface onsite increases by at least 0.25 of an acre (See Questions 4.3 through 4.6 below for examples). Please note that new discharges within the special water resource protection area must meet a 95% TSS removal rate, regardless of whether or not the site is redeveloped.
