That underground video shows what West Seattle Reservoir in Highland Park looked like three years ago, before the city finished covering it and filling it with water – one of two now-buried reservoirs in WS, along with Myrtle Reservoir between High Point and Gatewood.

While they’re out of sight, today they are not at all out of mind: While Seattle Public Utilities insists there are “no safety issues,” they confirm that both of West Seattle’s underground reservoirs – along with two others in the city – are undergoing seismic evaluations, to determine whether there’s a chance they might leak if there’s an earthquake.

This story broke last night at SeattleTimes.com (WSB partner); reporter Lynn Thompson writes that a firm that worked on the projects brought the potential problem to the city’s attention, saying their seismic calculations were based on above-ground structures, not underground ones. We talked about the report with SPU spokesperson Andy Ryan, who says test results won’t be in till spring, and once they are, if they show a potential seismic risk, then they’ll decide how to handle it. “We don’t expect that this is going to cost the public any more,” Ryan told WSB, pointing out that they recovered almost the entire cost of work done three years ago after Myrtle and Beacon Reservoirs’ waterproofing membranes were found to be leaky. (We broke that story here on WSB in July 2009, researching and reporting it after watchful neighbors noticed unusual work at the site and started inquiring. As Thompson’s story in The Times notes, the city and its contractors settled that case two years ago.)

Ryan says the seismic discovery – not related to the waterproofing issue, though both involved the design firm MWH – is not new; the evaluation, involving “sophisticated modeling,” has been in the works a while: “We have been working for a year and a half to get this modeling set up, to find the right people.” He stresses there is no current safety issue, no leakage – they just want to be sure there wouldn’t be, even in case of catastrophe.

One more thing we’ll be checking on: Both reservoir-covering projects in West Seattle led to the development of new park space. Myrtle is done, but WS (adjacent to Westcrest Park) is not – so we will check with Seattle Parks to see if waiting for evaluation results there might affect construction plans there.