Pumping Plant 1A was the District’s first plant, constructed in 1915, and has the second-greatest nameplate pumping capacity of any plant in the District. It is co-located with Plant 1B across Garden Highway from District headquarters in the southern portion of the basin. Due to its age and difficulty starting and operating, Plant 1A has not been operated in over 20 years.
Plant 1A's pumps are Byron Jackson pumps which were constructed between 1910 and 1912.
Of the regularly used plants, Pumping Plant 1B has the largest reliable nameplate pumping capacity. The plant was originally constructed in 1959 and then reconstructed in 2003.