please help! im building a one acre pond on my land. my dam will be 180 feet across and about 12 foot high. it will join two bottoms together. i started digging my core out. it was going great until i got close to the spring feed creek. i started hitting limestone about 2 foot down. i tried digging past it. after about 8 foot it started getting harder to dig but it's still limestone. water is running in the sides as i dig. what now?