Drinking Water Supply
BWL draws 100 percent of its water from wells which pump almost entirely from a layer of water-bearing sandstone 100 to 500 feet below the surface – the Saginaw Aquifer. The Saginaw Formation is shielded in most places from direct contact with the surface by layers of clay and shale, so contaminants do not easily get into the water at that level.
The 124 wells that make up the BWL system pump an average of approximately 19.2 million gallons per day (MGD) to either of two water conditioning plants. That's a lot of water! However, long-term measurements of the aquifer show that levels have not gone down overall and that the supply will be adequate for many years to come.
Water Conditioning
Soften
The BWL’s raw water supply is of great quality and only needs minor conditioning before distributing to our customers. The water received at the plant is softened, disinfected, and filtered. The raw well water has an average of 450 parts per million (ppm) hardness. The BWL uses a lime-soda ash process which removes excess calcium and magnesium, leaving an average of 97 ppm hardness in the finished water.
Disinfect
One of the key factors in the maintenance of good water quality lies in the establishment of a disinfectant residual. The BWL relies on the use of a type of chlorine called chloramine. Chloramine, which is a compound made up of chlorine and ammonia, has a number of advantages over "free chlorine."
- First, it lasts longer. As water travels through mains, it loses its residual much more slowly than it would with free chlorine. That means that less must be applied at the water conditioning plant to achieve a residual near the end of the system.
- Second, it imparts very little odor or taste. We are all familiar with the "swimming pool" odor of highly chlorinated water that detracts from its appeal. People seldom notice any odor from chloraminated water.
- Third, it results in lower disinfection by-products. Regulated compounds like trihalomethanes and haloacetic acids are reduced by up to 90 percent compared to waters using free chlorine.
Filter
The final step is filtration. The BWL uses sand filters for final clarification of our water, which ensure quality and great taste.
Additional Processes
Corrosion Inhibitor
Reducing the water's corrosiveness is important to keeping lead out of drinking water. In December 2016, the BWL replaced its last known active lead service line, but the BWL does not control the plumbing in the customer’s home or business. The BWL uses a phosphate compound to coat water pipes and prevent leaching of lead and copper into drinking water, which has shown past success in reducing lead levels. The level of corrosion control leaving our Water Conditioning Plants is tested every 4 hours and 30 minutes to confirm that proper levels of the additive are present. Also, quarterly sampling results from the distribution system are used to confirm that the proper additive levels are present throughout the BWL's service territory following treatment.
Fluoride
The raw water coming into our two water conditioning plants has a naturally occurring level of fluoride at approximately 0.35 ppm. The BWL adds fluoride to the water to bring it to the optimal level of 0.7 ppm recommended by the Center for Disease Control and Prevention (CDC) and the U.S. Public Health Service and approved by the EPA.
Water Distribution
After conditioning, the water is then pumped from one of the two Water Conditioning Plants over 800 miles of underground mains under pressure to our customers. The maintenance of that pressure ensures that when leaks occur, the leakage is of conditioned water out of the main, not of dirty water into the main. The BWL monitors water quality throughout the year at representative sites across the distribution system.
By conditioning the water, the BWL is able to stabilize the water brought to your tap. In maintaining consistency in the conditioned water, we offer you the ability to tailor the water to your use. The BWL Typical Analysis of Conditioned Water may give you an idea of what ranges you might expect for a variety of chemical measurements.