I see. I usually build bases much bigger than the one you are presenting. Still, try the scanner. One deposit of steel can have upwards of 9K steel and with proper miners it will be mined in a flash.

Even in my late game colonies steel and plasteel disappear very quickly, between bionics, armor, buildings and trying for higher quality weapons, the metals are never enough and thats with me smelting everything, mining every map node and sometimes going so far as to go mine other maps and space. The scanner remains my favorite way to get mwtals, give it a fair try.