Millions of dollars in expansions and improvements to the sewer system will be needed to handle Peachtree City's build-out population by the year 2007, the Peachtree City Water and Sewer Authority learned this week.

Wynne Grubbs, engineer with WASA's contract firm of ARCADIS Geraghty and Miller, outlined both a facilities plan and a plan for sludge management at the authority meeting Monday. It was the firm's initial report in a $125,000 study of the system and its future needs, designed to identify problems and to outline options for the authority to consider, said WASA manager Larry Turner.

Grubbs set the build-out population at 42,100, including a potential annexation of 5,100 residents of a future "west village." The system presently has a state permit to process 4.9 million gallons per day (mgd) of waste water, and 5.32 mgd capacity will be needed by 2007, Grubbs said. Turner commented that once all the data is in, he would recommend expansion by 1.5 mgd instead of 1.32 mgd, because the cost difference would be "negligible" and "that extra cushion would be money well spent ... water quality standards may change and become more stringent" by 2007.

The system is now handling 2.6 mgd in residential waste; 426,000 gpd (gallons per day) for commercial users, and 451.000 gpd for industrial customers, for a total of about 3.5 mgd now. Residential use is expected to rise to 3.5 mgd; commercial to 561,000 gallons, and industrial to 1.25 mgd. The system will reach 85 percent of its capacity by mid-1999, Grubbs said, which is the reason for looking at the future at this time.

The city bought the system from privately owned Georgia Utilities Co. two years ago in a controversial $29 million deal negotiated secretly by the city council that netted owners Doug Mitchell and Steve Black more than $5 million.

The study cites the option of "decommissioning" the Flat Creek treatment plant, which Grubbs said has "served past its useful life." While eliminating the plant and expanding Line Creek and Rockaway would be expensive, upgrading and expanding Flat Creek would amount to virtually building a new plant, since the present location "does not have enough capacity" even for a temporary expansion permits while new facilities were under construction, he said. Decommissioning would cost about $4.6 million and upgrading about $4.9 million, not including any other system upgrades or improvements, and there could be another problem with taking Flat Creek out of service, Grubbs noted.

The Flat Creek plant is presently processing .9 mgd and discharging the treated wastewater into Flat Creek, Grubbs said. It's possible that EPD might require that amount of water to be pumped back to that point from other plants, he said, to maintain the wetlands that were created by the placement of the treatment plant at that location. Also, the aging Flat Creek plant costs so much more to process wastewater than do the newer plants, said authority member Ray Helton, "that we lose money for every gallon that goes through."

But before any of the phased-in improvements are made, Turner added, a watershed assessment study, covering all factors that affect water quality in Peachtree City, would have to be completed.

Grubbs said the authority also will have to decide how to handle more than double the amount of "bio-solids," the sludge left after wastewater is extracted and treated. The system now is "landfilling" about 900 tons a year; Grubbs estimated that build-out will see about 1,852 tons a year.

One of the options he offered involved "contract composting," a method whereby bio-solids are mixed with other organic materials (such as peanut shells), stabilized and turned into crop fertilizer. He described the method as "the most environmentally friendly, and has a beneficial reuse," and said it is not the least costly of disposal methods but not the most expensive either.

Another alternative for sludge disposal would be land application, Grubbs noted. That method requires further treatment of the solids, but the authority does have a 275-acre site available where it could be done, he said, located off Ga. Highway 85 about eight miles from the Rockaway treatment plant. The authority presently has a contract with United Waste for transporting and disposing the bio-solids, Turner said.