Washington Administrative Code › Title 173 - Ecology, Department of (See also Titles 197, 317, 372, and 508) › Chapter 173-245 - Submission of plans and reports for construction and operation of combined sewer overflow reduction facilities › Section 173-245-020 - Definitions

Current through Register Vol. 24-14, July 15, 2024
As used in this chapter:
(1) "At-site treatment" means treatment and
			 discharge of combined sewage at the CSO site.
(2) "Baseline annual CSO volume and
			 frequency" means the annual CSO volume and frequency that is estimated to occur
			 based upon the existing sewer system and the historical rainfall
			 record.
(3) "Best management
			 practices" means use of those practices which will best reduce the amount of
			 pollution caused by nonpoint sources so that pollutant loadings in combined and
			 storm sewer flows during rainfall events are minimized.
(4) "Combined sewage" means the mixture of
			 sanitary sewage, infiltration, and inflow.
(5) "Combined sewer" means a sewer that has
			 been designed to serve as a sanitary sewer and a storm sewer, and into which
			 inflow is allowed by local ordinance.
(6) "Combined sewer overflow (CSO)" means (a)
			 the event during which excess combined sewage flow caused by inflow is
			 discharged from a combined sewer, rather than conveyed to the sewage treatment
			 plant because the capacity of either the treatment plant or the combined sewer
			 is exceeded.
(7) "CSO reduction
			 plan" means a comprehensive plan for attaining the greatest reasonable
			 reduction of CSOs at the earliest possible date. The requirements for a CSO
			 reduction plan are as further described in this chapter.
(8) "Department" means the department of
			 ecology.
(9) "Disinfection" means
			 the selective destruction of disease-causing and bacterial indicator group
			 organisms.
(10) "Domestic
			 wastewater facilities" means any CSO treatment or control facility included
			 under the definition of domestic wastewater facilities as defined in chapter
			 173-240 WAC.
(11) "In-line storage"
			 means storage of sewage within the sewer pipes through the use of regulators
			 and gates.
(12) "Infiltration"
			 means the addition of groundwater into a sewer through joints, the sewer
			 material, cracks, and other defects.
(13) "Inflow" means the addition of
			 rainfall-caused surface water drainage from roof drains, yard drains, basement
			 drains, street catch basins, etc., into a sewer.
(14) "NPDES" means the National Pollutant
			 Discharge Elimination System.
(15)
			 "Off-line storage" means storage of sewage adjacent to the sewer pipe in a tank
			 or other storage device.
(16)
			 "Primary treatment" means any process that removes at least fifty percent of
			 the total suspended solids from the waste stream, and discharges less than 0.3
			 ml/l/hr. of settleable solids.
(17)
			 "Sanitary sewer" means a sewer that is designed to convey sanitary sewage and
			 infiltration.
(18) "Sanitary
			 sewage" means the mixture of domestic, commercial, and industrial
			 wastewaters.
(19) "Secondary
			 treatment" means any process that achieves the requirements of 40 C.F.R. Part
			 133 as supplemented by state rule and guidance.
(20) "Storm sewer" means a sewer that is
			 designed to convey surface water drainage caused by rainfall.
(21) "Storm sewer/sanitary sewer separation"
			 means construction of new storm sewers or new sanitary sewers so that sanitary
			 sewage and surface drainage are conveyed in different sewers.
(22) "The greatest reasonable reduction"
			 means control of each CSO in such a way that an average of one untreated
			 discharge may occur per year.
Statutory Authority:
				  RCW
				  90.48.110. 00-15-019 (Order 00-07), §
				  173-245-020, filed 7/11/00, effective 8/11/00. Statutory Authority:
				  RCW
				     90.48.035. 87-04-020 (Order DE 86-34), §
				  173-245-020, filed 1/27/87.