Frequently Asked Questions
What is the authorized depth and area the Corps maintains?
Congress has authorized a channel 18 feet deep and of such width as can be practically and economically obtained through the bar. The authorization also allows a channel 200 feet wide and 18 feet deep from deep water in the bay to Miami Cove.
Has Tillamook Bay been zeroed out for dredging dollars because it is a shallow draft port?
Tillamook Bay is one of hundreds of small projects nationwide that were not funded in the President’s proposal budget for fiscal year 2004. If future channel dredging is required, funding would require Congressional action.
When was the channel last surveyed?
The entrance and offshore approaches to Tillamook Bay were last surveyed the week of June 23, 2003. It was scheduled to be surveyed in July 2003 but was pushed forward to obtain valuable information to assist investigation efforts. Click here to see the results from the past two years of surveys.
What were the results of the survey? Is the channel deep enough?
The survey showed that the authorized entrance channel is deeper than its authorized depth of 18 feet. The shallowest part of the channel was 23 feet deep. In fact, many areas of the channel were much deeper than previous year. The channel is well within its designed limits. The Corps surveys the channel each summer. Click here to see the results from the past two years of surveys.
What steps can the channel users take to assure safe passage when maneuvering the bar?
The Corps of Engineers has several safety tips for people crossing the bar. Please check weather conditions carefully before you leave. Pay attention to Coast Guard advisories and warnings. Be very careful when choosing a departure time. Learn about and become aware of both waves and currents and their patterns of behavior. The Corps also would like to remind you to always wear your life vests. For more safety information, please visit the U.S. Coast Guard Marine Safety Office website.
What role does the Corps of Engineers play in safety at the entrance of Tillamook Bay?
Within the limits of the statutory language and available funding, the Corps maintains the entrance channel and jetties to the maximum extent possible. The Corps also identifies other avenues that should be pursued should an issue be raised that requires attention outside of normal operations.
What has the Corps done so far with the $315,000 congressional add to study the jetty?
The $315,000 congressional add was intended for the development of a maintenance report for the jetties. Digital terrain models of both north and south jetties have been created and analyzed to identify degree of damage and cause of damage along each structure. Ebb tidal shoal surveys have been examined over time to identify potential changes that could impact the required design of the repair of both jetties. Preliminary design analyses have been conducted addressing existing condition and three potential alternatives for each structure. A revetment also has been designed to protect the root of the north jetty. Investigations into geotechnical stability of the rock jetties and rock availability for repair also have been conducted. Hydrodynamic modeling of the entrance has been conducted to aid in defining the design climate for jetty repair and identifying the optimum length of repair. Preliminary cost estimates for jetty repair have been initiated. Possible jetty repair plans have been drawn up for consideration.
When will the maintenance report be complete?
September 2003.
After the maintenance report is complete, how soon can the public expect the jetties at Tillamook to be repaired?
There was no funding set aside for jetty repair in the president’s tentative fiscal year 2004 budget. However, if construction funding is made available in the final 2004 budget and appropriated by Congress, repairs to both jetties could be conducted summer 2004.
Will repairing the jetties make the bar safer?
Yes. Repairs to the jetties will provide some improvements to conditions and the potential range in conditions at the Tillamook entrance.
Would navigation in and out of the entrance be safer if the bar offshore Tillamook Bay was dredged?
Many believe that dredging the channel deeper would improve navigation at the Tillamook bar; however, the Corps believes that dredging the offshore bar deeper may not improve the overall situation in Tillamook. Dredging the offshore bar could improve navigation over the bar, but could possibly degrade navigability at and within the jetty entrance and jeopardize the stability of the jetties. To reliably assess the overall effects of dredging the offshore bar at Tillamook entrance, a focused evaluation would need to be performed.
At present, the shallowest depths over the bar vary between 23 and 26 feet. This is five to eight feet below the authorized channel depth for the entrance.
During some offshore wave conditions, waves can break over the present bar configuration. The bar helps protect the jetty entrance from large waves by causing the waves to break offshore before the larger waves get to the jetty entrance. If the bar were dredged to prevent wave breaking over the bar, the result would be much larger waves at and within the jetty entrance.
The large waves would likely make navigation within the entrance itself (between the jetties) less safe than at present. There would likely be other consequences arising from dredging the bar.
One of these possible consequences is that the bar serves as a “conveyer-belt” to by-pass littoral sediment (beach sand) around the entrance. Altering the bar will likely result in significant erosion north or south of the jetties, likely jeopardizing the north jetty root. Another potential consequence is that larger waves at the jetty entrance could accelerate the deterioration of both jetty heads, which would cause additional hazards to navigation at the entrance.