By Rick Smeriglio for SCN —
Resurrection River flows to the sea through a broad plain between the mountains. Territorial authorities in 1920 built a gravel landing strip at the extreme downstream end of the floodplain. No other suitable place existed then. Seward has no other place for an airport now. Because the dynamic river will not go away and will not stay put, Alaska DOT&PF has a problem keeping its airport high and dry. As part of their Seward Airport Improvement Project, DOT&PF and the Federal Aviation Administration will consider alternative ways of keeping Resurrection River away from the runways.
Lower Resurrection River tumbles huge loads of gravel downstream while on its journey to the sea. Over time, as gravel builds up toward its downstream end, the streambed rises and forces the river to shift course. Resurrection River has moved hundreds of yards east to west and now sluices against the main runway on the east side of the airport. Heavy autumnal rains swell the river, causing it to escape its banks flowing to lower ground. It has overtopped the runway numerous times over the years, especially in 2013.
DOT&PF hydrologist Paul Janke said, “The problem is that Resurrection River is a braided river which means it is not just one channel; it’s numerous channels. There is a tremendous amount of sediment that comes down the river, primarily from Exit Glacier. When the river gets downstream of the Seward Highway, the slope on the river is less than it is upstream so the moving river cannot push all the sediment into the bay. The sediment falls out and it’s forcing the river to move. In this case, the water is moving toward the runway … The river has been overtopping the runway more frequently. In 2013, the runway was overtopped ten times. We’ve had erosion problems. The problem is that the middle third of the runway is a FEMA mapped floodplain meaning that it is the main channel of the river.”
Janke went on to explain that raising the elevation of the runway significantly (seven to 12 feet) above the floodplain would shift water back to the east and cause flooding and erosion to private property in the area. Janke said that would create a liability for DOT&PF. His agency would have to purchase the property. He said that historically, before human development, the river gushed out of the mountains and then slowed as it spread out across the broadest part of the floodplain.
“With human development we have constrained the river. The sediment can‘t spread out.”
Janke did not think that periodic dredging to remove sediment and gravel would work. As a hydrologist, he favored the idea of maximizing the width of the floodway consistent with existing development.
“I don’t believe that dredging would last very long. It would be very expensive; it would have to be year after year after year continuously forever just like port of Anchorage. Then you would get a big discharge and it would fill up whatever you dredged and it would be of no value,” said Janke.
Royce Conlon, PE, works as a civil engineer for and president of, PDC Inc. Engineers, the firm hired by DOT&PF to design the airport improvements. She serves as the project manager for PDC. She characterized her firm as just in the beginning phases of the project where it does not yet know what to design.
When asked why DOT&PF needed to do anything at all other than maintenance for the airport, Conlon said, “If the river wasn’t doing what the river is doing, we probably wouldn’t even be here. We were hired by DOT to develop a long-term solution to the flooding that occurred in 2013. The flooding of 2013 raised the bar enough that they realized they needed to have a long-term solution. The cost of maintaining was getting more than they could handle … they were literally dumping money into the river. Our project is to develop a long-term-sustainable facility.”
The runway pavement now has a weight restriction of 12,500 pounds whereas previously, C-130 cargo aircraft, which when fully loaded have landing weights of up to 130,000 pounds, touched down in Seward. DOT&PF project manager Barbara Beaton said via e-mail that her agency had no records of the designed weight limits of the main runway as designed in the 1950s. She wrote that, ” … it was obviously built for aircraft heavier than 12,500 pounds.”
Conlon said, “The theory is that when the water rose … it removed the fine materials … the glue … from between the larger rocks [in the runway fill] … We don’t have testing before and after … We know through testing that there is not adequate strength to the pavement to allow heavy loads.”
Seward city manager Jim Hunt said of the airport, “There’s an old saying in rural areas that if you lose your airport, your town dies … it’s a key economic component … it’s important for emergency response, for the businesses across the bay … it’s especially critical in supporting this side of south central Kenai [peninsula]. A couple of years ago we had multi-state military training and practice. Because of the fact that the airport was closed, it meant that they couldn’t bring some of the aircraft that were going to be a key component of the exercise, in … We’re going to do everything we can do to preserve the airport.”
In regards to the reduced weight load-limits currently placed on the airport Hunt said, “The impacts are several, but one of the critical effects is the ability of Life Flight and Life Med to come in with their larger planes, the larger twins, their jets. You know, we’ve had some fairly well known business people out of Seattle who have wanted to bring their private jets in for meetings. For instance, Paul Allen when he had his yacht here. They wanted to fly in some people because they were meeting with the Rasmussen Foundation and they couldn’t come in. They couldn’t bring their planes in.”
Planners for the project have three alternatives under consideration. All alternatives will accommodate aircraft with requirements up to those of a Beechcraft King Air B200 (runway load limit 12,500 pounds, runway length at least 3,300 feet.) Air ambulance services in Anchorage currently use this aircraft. All alternatives call for rebuilding the airport runways to accommodate airplane design group II (wingspan less than 79 feet) and airport approach category B (approach speed less than 121 knots). According to Beaton, data on aircraft use of the airport show than almost all use fits these categories. Beaton said that while the FAA will fund almost 94 percent of the project, it would only support building airports to accommodate existing and reasonably projected growth.
Current alternative 1.1 calls for raising existing runway 13-31 (main runway, east side) in place and armoring it with rip-rap rock to protect it from Resurrection River. Alternative 2.1 calls for closing runway 13-31 and raising runway 16-34 (shorter crosswind-runway, west side) and shifting it eastward while protecting it with rip-rap. Alternative 3.0 does everything that alternative 2.1 does and also extends runway 16-34 to 4,000 feet long.
When asked if the City of Seward could accept a designed load limit of 12,500 pounds and a designed runway rating of BII, Hunt said, “We would want to have the higher rating. We have to have the ability to receive larger planes, cargo, transport … It would make no sense at all to rebuild and repair it to the standard that it’s limited to now.”
“Number one, and I didn’t see it addressed, [at the open house meeting] the number one issue is the river, maintaining, dredging, moving, the river. Nothing can be done until the river is addressed, in my opinion,” Hunt said.
The public comment period for this phase of the project closes May 13, 2016. For additional information go to the project’s website at www.state.us/creg/sewardairport