PRESTRESSED CONCRETE WASTEWATER TREATMENT TANKS
INCORPORATED During the last quarter century, many changes have taken place in the concrete tank industry. Always at the forefront of new technology, DYK has emerged as the undisputed leader in liquid storage tank research and development. Included in its impressive repertoire is approximately 200 million gallons of wastewater treatment storage experience. Presented herein is a pictorial review of some of the most notable wastewater projects that DYK's personnel have participated in. If any of your present or future plans should include the design and/or construction of wastewater treatment tanks, DYK can provide whatever assistance you may require. After careful investigation of the different types of tanks available, we believe you will agree that the enclosed represent the state-of-the-art in wastewater storage facilities. Galvanized circumferential and vertical prestressing is used to keep the concrete in compression under all loading conditions, such as those caused from hydrostatic, thermal and seismic loads. A concrete wall that does not use prestressing, but instead relies on conventional reinforcing steel, will become tensioned as the tank is filled. By using prestressing, the wall is kept in compression and, as has been proven in thousands of structures, the result is a long lasting, crack-free, leak-free, tank that requires virtually no maintenance. Beadblasting Strandwr apping Shotcret eting To help eliminate bending stresses in the corewall, and to more effectively counteract seismic forces, unrestrained connections are provided between the wall, floor and roof. Bearing pads are utilized for separation and support with pvc waterstops incorporated to prevent leakage through all joints. Galvanized strands encased in neoprene sleeves provide the required shear resistance to seismic forces without inhibiting wall movements. A prestressed wall can also handle large openings, roof supports, launders, access ways and the many other appurtenance details often required of wastewater treatment storage tanks. COVER Point Loma Treatment Plant San Diego, California DYK's newly developed automated beadblasting process selfcontains its emissions and uses steel beads to clean and etch the tank wall instead of conventional abrasives like sand. DYK's state-of-the-art strandwrapping machine can apply 3/8" dia. galvanized strand at a rate of 250 feet per minute while maintaining a force tolerance of +1% and providing a continuous electronic recording of all applied forces. DYK's 3-in-1 machine can also apply wet-mix shotcrete over the wrapped strand. Continuous nozzle travel ensures uniform coating thickness and maximum quality control of the shotcrete.
D esigns incorporating vertically post-tensioned, cast-in-place corewalls were used to construct the sixteen 4.0 million gallon prestressed concrete digesters for the County Sanitation District of Los Angeles. Future maintenance expenses were further minimized by requiring that the tank walls be circumferentially prestressed with galvanized strand installed by state-of-the-art wrapping machinery having continuous electronic recording capability. For aesthetics, the digesters were half buried and architecturally treated with plaster relief above-grade. Project: Owner & 16-4.0 million gallon prestressed concrete digesters (125' inside diameter x 41.8' wall height) County Sanitation District of Los Angeles, Whittier, California 1
INCORPORATED Project: Owner: 2-0.75 million gallon prestressed concrete digesters (60' inside diameter x 30' wall height) City of Richland, Richland, Washington R. W. Beck & Assoc., Seattle, Washington A fter careful consideration of the long-term maintenance benefits of prestressed concrete, the City of Richland chose to use prestressed concrete instead of conventionally reinforced walls for their new digesters. Galvanized vertical and circumferential prestressing, combined with the inherent advantages of poured-inplace corewall construction, provided the City with cost-effective, low-maintenance concrete digesters. An integrated control building was located between the two tanks to maximize site usage and allow for future plant expansion. 2
W hen the San Jose/Santa Clara Water Pollution Control Plant decided to expand its wastewater treatment facilities, the tank design criteria included such limitations as floating roofs with supporting corbels, large pipe/manhole penetrations through the wall and reduced maintenance expenditures. It was decided that a concrete wall design utilizing close-tolerance applied, machine-wrapped prestressing would best accommodate all of these variables. By requiring the use of vertical post-tensioning and electronic force recording of galvanized circumferential prestressing, the joint Owners were ensured of receiving superior concrete structures. Project: Administrator: 5-3.0 million gallon prestressed concrete digesters (110' inside diameter x 40' wall height) City of San Jose, San Jose, California JMM/CH2M-Hill, A joint Venture, Walnut Creek, California 3
INCORPORATED T he Fiesta Island Replacement Project is an integral part of the City of San Diego's wastewater treatment expansion program. All seven of the prestressed concrete storage tanks have hopper bottom floors and flat roofs. The vertically post-tensioned cast-in-place corewalls were circumferentially machine-strandwrapped and lined on the interior surfaces with pvc. Galvanized prestressing steel, electronic recording of all applied forces, automated shotcrete and prestressed concrete tank design/construction experience were all mandated by the City to help ensure that these tanks would be built efficiently, economically and to the highest quality control standards. 4
Project: 2-0.5 million gallon prestressed concrete receiving tanks (45' inside diameter x 48' wall height), 2-1.4 million gallon prestressed concrete storage tanks (70' inside diameter x 48' wall height) and 3-3.1 million gallon prestressed concrete digesters (105' inside diameter x 48' wall height) Owner: Construction Manager: Tank Designer & Builder: City of San Diego, San Diego, CA Metcalf & Eddy, San Diego, CA SVERDRUP/ICF Kaiser Engineers, San Diego, California DYK Incorporated, El Cajon, CA 5
INCORPORATED Project: Owner: 3-2.5 million gallon prestressed concrete digesters (100' inside diameter x 41' wall height) Municipality of Metropolitan Seattle, Seattle, Washington Black & Veatch, Kansas City, Missouri: (digesters #4 & #5 constructed in 1986) CH2M-Hill, Bellevue, Washington: (digester #6 constructed in 1995) T he three digesters for the West Point Treatment Plant represent the latest in wastewater storage tank technology. The poured-in-place corewalls were post-tensioned both vertically and circumferentially using galvanized prestressing steel. The vertical post-tensioning units were further protected by the injection of epoxy grout into the vertical ducts that encapsulate the thread bars. Concrete architectural panels were placed around the tank circumference to match the enhanced aesthetics of the existing digesters. 6
T he City of San Diego was so pleased with their first four prestressed concrete digesters constructed in 1962, that in 1971, in 1986 and again in 1997, additional wastewater tanks were constructed. This is particularly noteworthy since these digesters not only store raw sewage, but are continuously subjected to airborne salt spray from the Pacific Ocean (only a few hundred yards away). Galvanized circumferential prestressing applied by close-tolerance wrapping machines and dense shotcrete covercoats have helped ensure a corrosion-free environment for more than 35 years. These quality structures are testimonials that long-lasting, lowmaintenance tanks can be economically designed and built. Project: Owner: 6-4.0 million gallon prestressed concrete digesters (125' inside diameter x 41.3' wall height), 1-4.5 million gallon prestressed concrete digester (125' inside diameter x 46' wall height), 1-3.5 million gallon prestressed concrete digester (110' inside diameter x 49' wall height) 1-0.25 million gallon prestressed concrete sludge holding tank (30' inside diameter x 38' wall height) City of San Diego, San Diego, California Holmes, Narver & Montgomery J.V., Los Angeles, CA: Digesters #1-4. City of San Diego, San Diego, CA: Digesters #5 & #6. John Carollo Engineers, San Diego CA: Digesters #6 & #7. Metcalf & Eddy, San Diego, CA: Sludge holding tank. 7
INCORPORATED T he North City Water Reclamation Plant will help supplement the City of San Diego's water resources through water reclamation. These prestressed concrete wastewater storage tanks are as impressive technically as they are aesthetically. Cast-in-place corewalls, vertically post-tensioned and circumferentially machine strandwrapped, provided quality assurances that future maintenance costs would be reduced. Architectural plaster bands around the tank were designed to blend with those of the staircase parapet wall and to match those of the Plant buildings. 8
Project: 2-3 million gallon prestressed concrete flow equalization basins (140' inside diameter x 30' wall height). Owner: City of San Diego, San Diego, California CH2M-Hill, San Diego, California Construction Manager: SVERDRUP/ICF Kaiser Engineers, San Diego, California 9 Tank Designer & Builder: DYK Incorporated, El Cajon, California
BUILT TO LAST 2-500,000 Gallon Receiving Tanks (45' diameter x 48' wall height), FIRP / NSPF Project Owner: Design/Build Tank Contractor: City of San Diego Metropolitan Wastewater Department Metcalf & Eddy, San Diego, CA DYK Incorporated, El Cajon, CA INCORPORATED PRESTRESSED CONCRETE TANKS P.O. Box 696, El Cajon, CA 92022-0696 Phone: (800) 227-8181 E-Mail dykinc@dyk.com