S93.15.16944

(From Creek & Watershed Map of Hayward & San Leandro. 1997. Janet M. Sowers and C. M. Richard. Published by the Oakland Museum.) Arrowhead Marsh was probably built up of earth washed down San Leandro Creek during construction, beginning in 1874, of the Lake Chabot Dam. Soil excavated from the dam site was dumped into San Leandro Creek below the dam. While the dam was under construction, an unexpectedly severe rain storm broke the partially built earthen dam, washing away 21,000 cubic yards of the dam's clay core along with much of the soil already dumped into the creek. A survey taken in l895 shows the new marsh filling the old creek channel and extending, in the shape of an arrowhead, into San Leandro Bay.