Complex sentence: Frustrated with the construction of the dam, Darling resigned and the Lawrence Land & Water Company completed the dam without him in 1873; however, only when J.D. Bowersock took over the dam in 1879 that the constant damage to the dam ceased and repairs held up.
Split into simpler sentences: Frustrated with the construction of the dam, Darling resigned and the Lawrence Land & Water Company completed the dam without him in 1873. However, it wasn't until J.D. Bowersock took over the dam in 1879 that the constant damage to the dam ceased and repairs held up.