Officials say Thursday’s sewage spill in one of Iowa’s biggest recreational lakes is no cause for alarm. The Department of Natural Resources says about 250 gallons of sewage and reject water from the water treatment plant spewed from a manhole in Okoboji and some of it reached the lake. Barb Lynch, supervisor for the D-N-R’s Spencer field office, says the spill was swiftly cleaned up.Lynch says the spill was caused by a plugged pipeline. She says there’ll be no impact on drinking water, boating or swimming at Lake Okoboji.She says all beaches are open. Bacterial samples were taken around the area of the spill and along the beach. The test results are due back later today but she says there is no cause for concern.