The sudden and dramatic draining of Augustana College's beloved slough on June 3 has turned into a blessing in disguise for the landmark campus water feature.
On that day, a city sanitary sewer pipe under the slough developed two holes about 18 inches apart, allowing slough water to rush into the pipe and, under great pressure, go whooshing down the hill. It found a "relief point" in an abandoned, opened-ended lateral pipe where it burst forth.
The force of the water washed away soil, causing a parking lot driveway to collapse, and it gushed up through manholes, throwing 100-pound covers into the air, and running into basement drains, sinks and toilets in several buildings.
The initial cleanup and repair was accomplished within weeks, but once done, campus administrators decided it was time to make improvements to be better stewards of the slough, said Kirk Anderson, vice president for finance and administration.
That is what's happening now.
The slough is once again drained and has been dredged of about 2,000 cubic yards of silt that had built up through the years, he said.
Another improvement was to remove a small dam that created a retention pond upstream from the slough. With removal, the slough was enlarged by 10 to 15 feet, Anderson said.
Because the draining last June revealed that one bank of the slough had eroded to the point that it was undermining an adjacent pathway, a 700-yard retaining wall made of wire baskets filled with rock aggregate has been installed from the college library to the president's house bridge, Anderson said. When the slough re-fills with water, this wall will be under water level.
Also while the slough is drained, the city of Rock Island is coming in to install a liner in the sewer pipe under the slough so that a break like that of last summer doesn't happen again, Anderson said.
The drainings have had another benefit: they have eliminated a large and growing population of thousands of non-native goldfish that likely originated in dorm room tanks. "From a biological point of view, this was a nice way to get rid of invasive goldfish that had changed the ecosystem in recent years," said Tim Muir, assistant professor of biology.
Some of the goldfish had grown to 10 inches long, he said.
These fish change the ecosystem by kicking up sediment on the bottom, which decreases the amount of light that penetrates the slough, thereby changing aquatic plant life, specifically phytoplankton, photosynthetic particles that float in water, Muir explained.
Goldfish also can out-compete native fish.
This spring, the slough will be restocked with natives including bluegill.
"Some real good came out of this," Muir said.
The final pieces of the improvement plan are to finish the paths with new asphalt, replace the lighting with LED bulbs and install native plantings.
The project cost is being paid for with a combination of insurance, institutional funds and $10,000 that came from alumni in a spontaneous burst of giving that occurred last summer when word spread through social media that the slough had drained.
The break provided a "great opportunity for us to focus on and restore one of the attractive elements of our campus," said W. Kent Barnds, executive vice president. "It's one of the most beautiful places in the Quad-Cities."