Item 5 - Ratify MWMC Budget - Laserfiche WebLink

Home Browse Search

~' ' · WHAT IS INFLOW AND increases treatment costs, and could accelerate WHAT ARE THE EFFECTS OF EXCESSIVE INFLOW ,~ INFILTRATION? treatment plant expansion. INFILTRATION? AND ' ~~;/~ Eugene has two separate During storms and periods of high groundwater, /vfl- ~ ~,,t' ·; / WHAT CAUSES INFLOW AND INFILTRATION? / -'1 I-'1 F1 I/''' / ''/ coLLection systems, a storm excessive I E I can cause a Large volume of water, , ,~ system for the coLLection of Like many cities, Eugene is beginning to experience which does not require the same treatment as rainwater and a wastewater system for the coLLection the impact of an aging wastewater coLLection system, wastewater, to access the wastewater coLLection of domestic and industrial wastes. The wastewater The greatest number of defects usuaLLy can be found system and enter the metropolitan wastewater coLLection system delivers wastes to the metropolitan in older wastewater Lines. Sewer construction in treatment facility. The increase from peak flows can wastewater treatment plant for processing prior to Eugene dates back to the [ate 1890's. MateriaLs used in surpass the capacity of the wastewater coLLection discharge to the WiLLamette River. Most of the City's constructing the older parts of the wastewater system and the treatment facility. When the system stormwater system carries rainwater to the Amazon coLLection system do not meet current standards for flow exceeds capacity of the coLLection system it can Creek or the WiLLamette River. minimizing I Et I. Investigation results using smoke back up (surcharge) into basements and sewage can Inflow and InfiLtration (I Et I) is a term used to describe testing, TV inspection, and other techniques show the overflow into streets through manhole covers. In the undesirable flow of rainwater or groundwater into highest concentration of problems caused by I & I in extreme cases untreated sewage could enter the older areas of the city. waterways. the wastewater coLLection system. InfiLtration enters the wastewater system as a result of structural defects A significant portion of inflow comes from private If sewage flows exceed capacity of the secondary consistent with an aging or damaged system. Inflow is property sources, such as, roof, area and/or treatment facility, which is 105 miLLion ga[tons per day defined as rainwater that enters the wastewater foundation drains connected to the wastewater (mgd), the excess flow is diverted to the WiLLamette system through a direct connection, such as improperly Lateral These types of improper connections which River without the added benefit of secondary at[ow the inflow of surface or ground water into the bioLogicaL treatment. In the summer, dry weather flow [~.owsou~r.~s wastewater system are prohibited by the Eugene at the treatment facility averages 23 mgd. During ~TION Municipal Code, section 6.610. heavy rain events wastewater flows increase to 9 times ';~QURCE~ (198 mgd), which exceeds the secondary treatment In addition to an aging public system, currently being capacity by up to 53%. It is very important to prevent rehabilitated by the City of Eugene, a major aL[ storm and ground water from entering the contributor of infiltration is defective private wastewater Lateral tines. The Lateral is the pipe that connects the building sewer to the public main Line Basemen~ FLooding which is usuaLLy in the street. Several studies from When the wastewater system Is overloaded, the water level in the manholes and the wastewater system rises. various regions around the United States suggest that When it dses above the [eve[ of the basement floor, the infiltration from private Lateral tines is the single ~ ,wastewater system can back up and Rood the basemertt. highest contributing factor to excessive wet weather ~--~ ~1~ ~ Water revel in basement matches "~+~:~::'~":~:~ ' ~='=~'" '"' ..... flows. Private Lateral Lines which were constructed. ~%1 I Il, water ~ev,L Courtesy oftheKfn, CountyRe, fonoll/I prior tothemid 1960's are typtca[ty high contributors III lllJ to infiltration. ExampLes of materials used during this \ connected roof drain, parking tot drain, or catch time period includes day, orangeburg, and thin watt _ _ _Z basins. I & I is found in private and public portions of concrete. Lateral tines constructed with these the wastewater coLLection system. Excess I & I is materials are past their useful Life expectancy and unnecessary and reduces coLLection system capacity, experience indicates the failure rate is increasing exponentiaLLy.