The Portland, Ore., Bureau of Environmental Services has several projects planned for dealing with stormwater. The top four projects are expected to cost the Bureau a total of $114.3 million.
One such project involves work on the Columbia Boulevard Wet Weather Treatment Facility (CBWWTF). The project will involve the construction of new primary clarifiers to treat up to 120 mgd of dry weather flows, modifications of existing primary clarifiers to treat up to 240 mgd of wet weather flows, expansion of the existing chlorination system, modifications of the existing effluent pump station, construction of a new dechlorination facility, and modifications of the screen house and odor control systems. The project will cost an estimated $37.4 million.
Four projects are planned to capture, store, convey and treat combined sewer overflows (CSOs) from the Columbia Slough basin. They include building and modifying treatment facilities at the Columbia Boulevard Wastewater Treatment Plant (CBWTP).
Another project in the Columbia Slough program is the $26 million Columbia Slough Consolidation Conduit, which will interrupt and collect the flow from 10 outfalls - a move that will handle most of the 13 outfalls that come from North and lower Northeast Portlands combined sewage discharges. Once the Consolidation Conduit and downstream treatment and outfall facilities are built, overflows will be reduced from 50 per year to once in wet weather conditions over a five-year period and once in dry weather conditions over a ten-year period.
The conduit is divided into six parts and will use pipe ranging in diameter from 36 inches to 144 inches. The last part of the project is an odor control facility.
A third project, the Tanner Creek Basin Stream Diversion, calls for the design and construction of a stream diversion pipe in the Tanner Creek basin to divert stormwater from the combined sewer system, providing increased capacity for sanitary sewage. Much of the stormwater runoff comes from forested areas in the upper basin and is clean enough for direct discharge to the Willamette River.
This project also would increase capacity in the West Central Interceptor, and at the Ankeny Pump Station and Treatment Plant which is needed for sanitary sewage. Further development of these basins will require pretreatment of stormwater prior to discharge. The city is considering locations for new pretreatment facilities and construction methods for future plans of the work.
The Tanner Creek Sewer Stream Diversion Project has been separated into four phases. The project is necessary to meet the Amended Stipulation and Final Order (ASFO) and must be operational by Dec. 1, 2006. It will cost about $22.4 million.
The four projects in the Columbia Slough program combine to form one larger project, making each smaller project ineffective by itself.
All four projects have to be constructed and operable by Dec. 1, 2000, and meet the ASFO requirements. If the projects are not operable by the deadline, DEQ can levy a fine of $1,000 per day for each compliance date missed and $2,500 for each outfall not controlled as required. Further enforcement can be taken under the NPDES permit and the federal and state clean water statutes.
Another major Portland project, called the Southwest CSO Control System, will incorporate combined sewer overflow controls from the California, Carolina, Lowell, Woods, and Sheridan systems. The key components of the control system include the building of a storage tank for the California system and two consolidation conduits.
