The other question you should be asking is: "How many tons/day can SNEY procure with their three dredges?" If I had to guess, they might be able to draw up to 10 tons per day per dredge assuming they gave an effective exploration team prepping sights ahead of each dredge team and they have sufficient spare parts to redeploy dredge 3. Of course, they will have to work out a transport barge system so that dredge 2 can be redeployed in order to get enough sand to feed the 4T/hr plant they want to build.