TROY MILLS — When a perfect summer afternoon broke a string of miserably humid days, Harold Annis headed for the bridge above the Troy Mills dam on the Wapsipinicon River.

"Better than sitting in the chair sleeping," Annis, 73, said as he dropped a pair of lines over the bridge’s railing. "They’ve really been biting."

Annis wet his lines off the east side of the bridge, about 30 feet downstream from the rain-swollen Wapsi’s tumble over one of Iowa’s 3,374 dams.

"I fish everything from this side," said Annis, nodding toward the snarls of fishing line and bobbers hanging from a power line on the upstream side.

Like the Lake Delhi dam on the Maquoketa River that failed July 24, flooding thousands of acres of farmland and causing millions of dollars of damage, the Troy Mills dam is a privately-owned gravity dam, one of only seven (since the loss of the Delhi dam) in the state.

A gravity dam is defined as a larger structure, almost always concrete, large enough to prevent breaching from the force of the water behind it. Eighty of Iowa’s dams are gravity type, and just eight were privately-owned, including Troy Mills and Lake Delhi.

A simple, seven-foot-high, 300-foot-long roller-type dam, Troy Mills lacks the adjustable floodgates housed in the 55-foot Delhi dam. When the Wapsi rises high enough, it simply flows over the top, preventing flooding along its 640-acre upstream impoundment.

Classified a low-hazard dam, Troy Mills is inspected every five years by the state Department of Natural Resources. Dams classed "high hazard" are inspected every two years.

A high hazard designation doesn’t mean a dam is a threat to fail, according to Lori McDaniel, supervisor of the DNR’s water resources division. The designation goes to dams located upstream from an area "where dam failure may create a serious threat of loss of human life," McDaniel wrote in an e-mail.

Just 101 Iowa dams are high-hazard, but only 12 of them have the required emergency action plan in case of failure.

"That’s one of our new program focuses, to encourage emergency action plans for all dams across the state," said McDaniel. "Right now we don’t have any requirement that owners have an EAP, but it is something we feel is important, and we’ll be encouraging them."

The Lake Delhi dam had a "partial" emergency plan, McDaniel said.

Nearly 3,300 of the state’s dams are simple earthen structures built to hold back water for a farm pond or similar function. Most such dams are privately owned, often by the family who built them, and most are relatively small.

Although the DNR has just two full-time dam inspectors, its inspections are up to date, McDaniels said.

"We contract with two part-time inspectors," she said. "We are able to keep up on inspections as they come up. When we have situations like the floods of 2008, we work around that and make sure we still get the dam inspections done."

A May 2009 inspection at the Delhi dam turned up damage to one of its three floodgates, The DNR gave the Lake Delhi Recreation Association until the end of the year to repair it, then extended the deadline. High water this spring and summer prevented crews from making the repair, according to lake association directors.

The last repairs to Troy Mills’ dam came in the fall of 2006, when about 40 volunteers repaired damage to its top and face. The deterioration since the dam was reconstructed in 1989 was speeded by road salt drained off the bridge carrying County Road W-45.

"We didn’t tell anybody, we just fixed it," said Gary Peiffer, 43, whose auto repair shop is just north of the river. "I don’t know what it cost us. All the labor was donated. I think we spent $2,500 on it."

The do-it-yourself effort shows the dam’s significance to its small community. Beyond creating boating and fishing for several dozen upstream cabins, the dam is Troy Mills’ reason for being: you can still see the mill race that once diverted the river’s flow to power Troy’s mill.

Jeanne Carson, secretary-treasurer of the Troy Mills Dam Association, estimated the group has about $4,000 in the bank. Unlike the Lake Delhi group, the Troy Mills organization doesn’t levy a fee against its members or property owners.

"They had a big dam party," said Peiffer. "That’s what they called it. If something happens again, we’ll pass the hat. When something needs doing, we do it. It’s a pretty good community that way."