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A lack of design standards requires engineering resourcefulness and creativity.

Challenge

GLHN worked with Pima County and the community of Arivaca to design a new evapotranspiration bed to replace an aging septic system. When GLHN engineers designed the ET bed to state administrative code, they found that the testing method for the sand no longer existed. The Pima County Department of Environmental Quality agreed that if GLHN proposed a material and tested it, Pima County would accept the test results. We had to find sand that could meet all of the code requirements as well as make water rise more than two feet by capillary action.

Solution

GLHN’s civil engineering department quickly transformed into a sand lab. With the help of a local contractor, we found a nearby sandpit and collected samples. We built the lab by taping 5 feet of tubing to a vertical surface, filling the tube with sand, and placing the end in a bucket with six inches of water. Within two days, 30 inches of the sand was wetted. DEQ approved the sand selection and the project went into construction. The new ET bed is over 7,000 square feet, averages 2.5 feet deep, and required over 50 truckloads of this special sand.

Role: Engineer of Record
Size: 9.0 acres
Cost: $150,000
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