GM Plant Will Save Millions of Dollars by Capturing Rainwater

by | Aug 18, 2016

GM stormwater retention pondEnvironmental managers are increasing looking to improve water management and efficiency to save money and resources now — and in the future.

The UN projects a 40 percent water supply shortfall globally by 2030 and this represents a $63 trillion risk to business and communities, according to CDP (formerly Carbon Disclosure Project).

Going about implementing water conservation projects, however, can seem daunting. Using recycled water, for example, can save millions of gallons annually but can be difficult due to funding and infrastructure challenges.

But through collaboration, both internally and externally, as well as creative thinking, companies can conserve water and save money, as General Motors’ new project to capture stormwater illustrates.

On its company blog, GM describes the GM Detroit-Hamtramck Assembly project, two years in the making, and says it will save the plant nearly $2 million annually.

It will also save water: the plant will reuse captured rainwater for manufacturing processes throughout the 4-million-square-foot facility.

“In one application, stormwater is pumped to an onsite power house where it is treated, fed through existing sand filters and then used in the plant’s cooling towers,” Al Hildreth, GM global energy manager, told Environmental Leader. “This process alone eliminates over 20 percent of the plant’s water usage and saves over $140,000 annually.”

Hildreth says the initial goal of the project was to avoid stormwater discharge fees from the city of Detroit.

The plant had two retention ponds onsite, but paid fees to send excess stormwater to a city treatment plant. “These fees made up 14 percent of the entire plant’s utility budget,” Hildreth said.

The solution? Build a third pond on the facility’s grounds.

In the third quarter of 2014, GM dug up more than 20,000 dump truck loads of dirt and created a third pond with a maximum retention capacity of 47 million gallons of water at one time, the equivalent of a 100-year storm event.

GM expects to see a return on investment in a little over a year.

“This two-year project took just under $3 million to complete,” Hildreth said. “The biggest expense was to dig a new pond, install interconnections between the ponds and storm sewer, and build a supply line to the power house. We also installed a new pumping system, carbon filtration tank and pumps, and refurbished and rerouted pipes.”

As the blog explains, the system works like this:

  • Rain enters storm drains across the site and then flows to the retention ponds.
  • Floating pumps transfer the water to the plant’s power house. GM used floating ponds, more typically used in mining operations, instead of submersible pumps.
  • The power house treats the water through sand filters before it feeds the plant’s cooling towers.
  • Carbon filters and reverse osmosis purify the remaining water. GM says future plans include Detroit Renewable Power turning that water into steam to heat and cool the assembly plant, as well as 145 other Detroit businesses.
  • GM then uses any reject water from the purification process to help break down the paint sludge left over from painting cars, saving $75,000.

Hildreth says the project required a great deal of collaboration, both inside the company and with the city of Detroit. Team members within GM included facilities and engineering groups, government relations, legal, finance, environmental, and global facilities departments.

“We also had to think creatively,” he said, pointing to the project’s use of floating pumps instead of submersible pumps.

“Traditionally, submersible pumps would be used to remove water from a pond, but these pumps are expensive and difficult to maintain. When they need to be serviced, all of the water has to be drained. To avoid draining precious stormwater, save money and work more efficiently, the team went outside the auto industry and found an innovative solution used in mining: floating pumps. Floating pumps are accessible, easy to maintain and can accommodate an elevation change of up to 40 feet. This solution was the result of working with the plant and GM’s facilities engineers.”

The stormwater project also moves GM closer to its goal of reducing water intensity by 15 percent by 2020 against a 2010 baseline at its global facilities. To achieve this target GM has implemented other water reuse projects, such as one at its Arlington Assembly will save 17.8 million gallons of water a year.

From 2010 to 2015, the company reduced its global water use by 10 percent.

Other companies can follow GM’s example and Hildreth offers this advice: “Look for solutions that will enable you to reduce your environmental impact while also delivering business value. The upgrades we made to repurpose all the rainwater collected also translated into cost savings.”

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