For more than 15 years, a pair of sewage treatment plants in eastern Tijuana have presented an opportunity – and a challenge. The plants, Arturo Herrera and La Morita, raised hopes for a major wastewater reuse effort in the city – for irrigation, construction and industrial use. … But without a network of pipes to deliver the plants’ discharge, most of that highly treated wastewater has gone unused. … Today, as Tijuana faces growing water shortages, authorities with the Baja California water agency, CESPT, are studying a solution: piping the plants’ discharge to a spot just upstream from A.L. Rodriguez Dam, for storage and eventual delivery to a plant that would convert it to drinking water. The project would be one of the first in Mexico that involves what engineers call “indirect potable reuse.”