Just looking at the tanks, the picture dates back to the 1950's at most.
I tried looking at the signs with a magnifying glass but couldn't make out any text that would have informed me.
The tanks have the Shell Oil logo on them, but there are no gas stations left in Port Lewis...
I took Google Earth and went along the famous Route 132 that crosses the town looking for a building with a diamond roof... couldn't find one that matched the corner entrance on that store.
In that area, the route roughly follows the river with the other side being entirely farmland...
I know it's not near the river as no important roads leads there... besides, all you can find there are million dollar properties that get flooded every spring.
So I guess the location is lost to history...
EDIT: I just looked at the history of Shell Oil logos. The logo on the tanks was used from 1955 to 1961.
Before that, the text on the logo was white. From 1961 and on, the logo was inside a red square. So that gives a 6 year bracket of time...