Tanks & Taps
Storage strategies for alternative water supplies
Storage tanks can be “friends or foes” to water, depending on the contents, contexts and contingencies. Recent events underscore the importance of thinking upstream and on site for the benefit of drinkers and water managers everywhere.
Chemical storage tanks fall into the “foe” category when they fail, particularly near community water intakes. Just ask the 300,000 citizens in and around Charleston, W.V., who lost use of their drinking water for five or more days after a Jan. 9 spill of a chemical (crude methylcyclohexanemethanol) used in coal processing and washing leaked from its storage tank into the Elk River and the Kanawha River, where the local water utility’s intake is located.
It hardly is breaking news that tanks leak or burst, especially in bitter winter. A similar crisis occurred in January 1988, when an Ashland Oil Co. tank in Floreffe, Pa., collapsed and spilled 4 million gal of product into the nearby Monongahela River and ultimately the Ohio River, contaminating drinking water for 1 million people. Lessons learned led to increased national requirements and liabilities for aboveground storage tanks under the Clean Water Act and the Oil Pollution Act.
Consulting the Past
Companies, utilities, regulators and emergency response planners all can learn from the Charleston spill, too. Contingency planning, onsite inspections and rapid response drills all take money and manpower. Any storage tanks located, or proposed to be located, so close to waterways and community water sources should get heightened scrutiny, whether the contents are oil, chemicals, animal fats, vegetables or minerals.
That seems to be the gist of early proposals by West Virginia officials and legislators. The governor and congressional leaders are championing efforts to strengthen planning and reporting requirements, as the West Virginia Department of Environmental Protection estimates there are more than 1,000 aboveground chemical storage tank sites throughout the state. Various proposals would require owners or operators of industrial aboveground storage tanks to conduct monitoring or testing, allow access to records and provide for various enforcement orders and penalties. Bill language also would require all public water systems to have written plans in place to prepare for emergencies, specifically in the event a contaminant is discharged into the water supply.
An ounce of prevention is worth a pound of chemical, a gallon of bottled water and more than you can measure.
Benefiting from Storage
Storage tanks also can fall into the “friend” category. Just ask the 2014 U.S. Water Prize winner, Orange County Water District and Sanitation District, Calif., for its Ground Water Replenishment System (GWRS): www.uswaterprize.org.
Since 2008, GWRS has been reclaiming wastewater, treating it to ultra-pure levels and discharging 70 million gal per day (mgd) underground to replenish and clean precious water supplies and also fortify a barrier against salt water intrusion. In 2011, leaders decided to expand the world’s largest planned indirect potable reuse project another 30 mgd. They ran into capacity problems, however, in trying to find the right amount of flow and being able to treat it either during the day or at night.
The solution: Use aboveground tanks to store excess flows of 15 million gal during the day that then can be treated at night, allowing the total goal of 100 mgd to be met over a 24-hour period. The tank plan adds $25 million to the cost of the project, but the payback is calculated at only two years and the storage strategy will allow full production of the facility.
And what could be more important than that, as the state and region endure a record drought and search urgently for alternative water supplies? The GWRS expansion, scheduled for completion in 2015, will result in approximately 31,000 acre ft per year of additional new water, enough to meet the water needs of nearly 250,000 Orange County residents. This feat, made possible by added aboveground tanks and other technological and efficiency improvements, will bring the total water production of the award-winning GWRS to 103,000 acre ft per year, enough water for 850,000 people.
A little storage (or in this case, 15 million gal) can go a long way in making the most of every day (and night) and planning for not-so-rainy days ahead.