Pumpkin-colored: Chester Creek on the morning of July 18. (by Brendan Babb)

Chester Creek and parts of Westchester Lagoon turned an opaque, pumpkin orange for a half hour or so the morning of July 18, generating a flurry of calls to the mayor's office and the Alaska Waterways Council looking for an explanation. That explanation never really came.

Pictures of the orange water near Valley of the Moon Park were featured on the news that night. Jerry Hansen, deputy director of project management and engineering for the city, told reporters the source of the orange was unknown and wasn't connected to city operations.

Chester Creek on Wednesday July 18. (By Dave Mayo-Kiely)

But Cherie Northon, head of the Waterways Council, wasn't sure about that. She suspected the orange water came from the storm water system. The creek turned orange once before when a city crew was clearing out a storm drain without following proper procedure, she said. She showed me pictures. They looked very similar to the ones I'd seen of the orange creek.

You might not think about it when you wash your car or water your lawn, but most all of the run-off from roads winds up in city's creeks. Those creeks flow into Cook Inlet. Usually storm drains filter out oils and some solids before the water flows into the stream. The city periodically services the drains.

Northon's hunch was that the creek had been polluted with storm water sediment. The sediment that collects in the storm drains turns orange because the water corrodes the pipes and iron leaches out. Storm water can be contaminated with road salts, dog feces, detergents and automotive pollutants, Northon said.

That isn't good for Chester Creek, but it's worth mentioning that the creek is contaminated with all those pollutants already. Dog feces from the trails is a particular problem. In the scheme of things, it's hard to say whether some storm drain sediment made a serious impact, even if it did look terrible.

I went back to Hansen from the city and told him Northon's theory. He denied that the city had anything to do with the orange creek this time. All the trucks were on the other side of town, he said.

But, he did send a team to investigate the bright orange water Wednesday afternoon. The creek had cleared by then, but found a number of work sites nearby, including a city contractor, Frawner Corp., doing testing in very old storm drains between A and C Streets. That is just upstream from the place in the creek where the water turned orange.

Hansen said there was no proof the storm drain work caused the creek discoloration. Was it a possibility? Maybe, he said. Frawner Corp. did not return my call.

An orange plume spreading out into Westchester Lagoon Wednesday, July 18 (photo by Jack Johnson)