Bureau of Water Works and Supply

I found this Benchmark Los Angeles Aqueduct Datum in the concrete east of the park.  As it is titled City of Los Angeles I think it must be from 1915 to 1937.  In 1915 the San Fernando Valley became part of  Los Angeles City and the Bureau of Water Works was renamed to DWP in 1937.  I've been trying to identify Benchmark No. 17, so far, without success.