By Darren Vogel, Project Manager
Water is a natural resource we seldom think about until we need it. Where does it come from? Where does it go? Is it clean? How much does it cost? Sometimes we forget that water is not a limitless resource, and – in fact – will become less available in the future as populations continue to increase. Which is why water availability and conservation have become two of the driving forces when planning for a new development and construction around the county.
The Vogel Bros. Florida office is heavily involved in the water and wastewater market segment. We appreciate the shift in focus and techniques being developed with water conservation in mind. Vogel Bros. has worked on several new and innovative treatment processes including projects with reverse osmosis, desalinization, aquifer recharge and storage, and advanced bio solids treatment. While any construction project can have its unique challenges, often these water treatment projects have components that are being constructed for either the first or second time ever. To successfully complete these projects, the Vogel Bros. staff often have to create new, one-of-a-kind solutions. What follows is a detailed look at a recent project that highlights the solutions one Project Manager created in response to the unique challenges of a water treatment project.
APOPKA NORTH SHORE RECLAIMED WATER TREATMENT FACILITY
In an effort to restore Lake Apopka and provide reclaimed water for the growing population of Eastern Orange County, Vogel Bros. recently completed the Apopka North Shore Reclaimed Water Treatment Facility. Designed by the City of Apopka and St. John’s Water Management District, this 12 million gallons per day, reclaimed water plant treats and utilizes surface water from the Apopka North Shore Restoration Area. The project included a mile of dredged and reshaped canal, feeding lake water into a 40’ x 20’ x 20’ deep intake structure. The water is drawn from the intake structure into a similar sized pump station which pumps the water into two filter beds. After being treated in the filter beds the water is collected in a transfer pump station roughly the same size as the intake structure and the water is then pumped through six submersible transfer pumps into a 3 million gallon ground storage tank and treated with chlorine. Once treated the water is pumped into the city’s reclamation system through three 350 HP vertical turbine motors.
The two lined filter beds for this project were first of their kind in the state of Florida. While the concept of filtering water is not new technology, the volume of water and size of the ponds is unique. Each pond bottom was roughly 600’ x 200’ and 13’ deep, creating a volume of water that is more than 21 Olympic size swimming pools. Due to the high turbidity of the surface water from the lake, the filters were constructed with a 30” layer of sand on top of an 18” layer of 57 stone with 14,000 LF of perforated pipe along the bottom. Taking into account the 4:1 side slopes of the ponds there was almost 40,000 CY of material that had to be placed in the ponds. That is enough material to fill a football field 14’ deep.
Typically when moving tens of thousands of cubic yards of material many cycles of traditional heavy equipment including excavators, loaders, and dump trucks would be used. However the HDPE liner and perforated HDPE pine in the bottoms of the ponds would be severely damaged by heavy traffic. Vogel Bros. had to find a way to evenly place the material as specified and as quickly as possible while maintaining safety and not damaging the liner or perforated pipe.
The first option was to use a crane to distribute the material 4 cubic yards at a time. Assuming a 6 minute cycle time and normal operation, it would take almost 8 months of constant motion to place all of the material. This option was too time consuming and not cost effective.
With past experience in the Central Florida phosphate industry, the Vogel Bros. team suggested implementing a belt system to move the material (much like how phosphate rock is moved around chemical plants). While researching this approach, Vogel Bros. contacted several specialty equipment providers in the phosphate industry, but could not find a belt system that was (1) easily moved around the top of the filters and (2) could reach out the 130’ to the center of the filter.
Finally, Vogel Bros. was introduced to Putzmeister Telebelts. These machines are normally used to place large, continuous amounts of concrete at rates of around 250 cubic yards per hour. The Telebelt operates under the same principles as a pneumatic pump trucks, however it uses a belt to move the material (instead of pumping the material).
Putzmeister’s corporate office directed Vogel Bros. to Hunter Concrete Pumping of Hutto, TX as the company who had machines closest to Florida. Hunter Concrete had several machines, but only one had a reach of 130’ from center pin to the end of the boom. Not only could the machine reach to where it needed, but it was able to drive along the top edge of the filters and set up in several different locations as needed! As long as Vogel Bros. could supply the Telebelt with a steady stream of material, the belt could continuously fill the filters with material.
After looking at the site conditions, an existing loading dock was used to stock pile the material. This location allowed the loaders access to take material to the Telebelt, and enough room for dump trucks to continuously deliver additional material. After sitting down and determining cycle times and travel distances, it was determined that three loaders with 3.5 cubic yard buckets were required to feed material. With this uniquely designed application, Vogel Bros. was able to average a placement of 225 cubic yards per hour. This reduced the material placement schedule from 8 months to 6 weeks!
By taking past experiences and applying it to a unique situation, Vogel Bros. was able to reduce the project timeline by over 6 month. This reduction in time in turn saved the owner costs both in general overhead and in hard costs of rental equipment and man power.