Well the article is funny - because it's stupid tripe!
Note where this guy has the placard being found! On the Columbia River! The guy needs to go back and repeat Coopergarten.
I fixed the map so the guy doesn't look so bad

Hold everything here! Everybody take a deep breath and take a look at a map of Washington State.
First, Castle Rock, WA, is at Interstate 5 Mile Post 49 which means it is 49 miles north of the point where I-5 crosses the Columbia River on the west side of Vancouver, WA. The "Castle Rock" on the original map is apparently actually "Cascade Locks" at Bonneville Dam which is about 30 or 40 miles east of Portland, OR.
As I understand it, the "Amboy chute" was found near the town of Amboy, WA and not 35 miles further north, and not north of Mt. St. Helens either.
I have no idea where the "1970 Search Area" came from, or what was being looked for at that location. 
The placard was not found at "Castle Rock" or "Cascade Locks", in any event.
This reminds me of another media error - pic below from 1980. Note their location of Tena Bar.
I lived in Washington State as a very young boy and was a Boy Scout. When I was there, Boy Scouts knew how to read maps, tie knots, and help old ladies across the street. It looks like things have gone down hill from that era.
Thats why there is something called honors classes - and competition for them is higher than ever and overflowing, I am glad to report. Kids qualified in every sense of the word and more. This makes it tough for the kids at the bottom.
While I have you, whats the highest elevation on Tena Bar you know of and where is it? Would you agree the elevation behind the fence line is roughly 20ft, and was that the case in 1980 ?
There is apparently no accurate data for the elevations (or contour lines) at Tina Bar since those lines are generally machine drawn on maps and are basically just estimates. And the contour interval there is 10 feet which means there probably won't be more than two lines anyway.
But we won't quit on the problem. When Meyer Louie and I was there in 2013, we talked to a fisherman named "Jon" who had the key to the Tina Bar gate and who told us that he had basically been at Tina Bar on a daily basis for about the last 50 years.
Jon pointed out a log (or railroad tie) that was about 10 or 15 feet north of the Tina Bar gate and on the fence line. Jon said that the log represented the highest river water level he had ever seen at Tina Bar. He also specifically stated that he had never seen any river water flow into the dairy pond on the east side of that fence and nothing flowing from the pond into the river.
My eyeball guess was that the log in question was about 15 to 20 feet above sea level. And let me emphasize the word "guess". There was nothing to measure it by and I did not know what the river water level was referred to sea level. But the log was about 2 feet (this is an accurate estimate) below the top of the bank separating the river from the pond and, again, it was right on the fence line.
From what I have seen of the Tina Bar area, including Shutter's recent photos, today's fence line is the same one that was there in 1980. So I would agree that the fence line, specifically the top of that embankment, was very close to 20 feet above sea level.
Recently, I think I saw in some article that the ground elevations near Tina Bar went up to about 40 feet at the highest point, but that point was not identified. Frankly, I doubt that is correct unless the writer was referring to the top of the Fazio's sand pile. Basically, I would estimate that most of the Fazio's property is between about 20 and 25 feet, or less, above sea level and perhaps up to 30 feet above sea level on the river bank about 200 or 300 feet north of Tom Kaye's money find location.
But in the area of the Tina Bar gate, an estimate of 20 feet above sea level is as accurate as you can get until someone determines the elevation of the river water level and then, using a transit or similar instrument, determines the actual height of the fence line and the embankment where it is located.