http://www.txpeer.org/toxictour/laredo.html
http://www.tceq.state.tx.us/compliance/monitoring/water/quality/data/wqm/mtr/riosum.html
A TDS meter will not detect Volatile Organic Compounds.
"The 30 chemicals that exceeded screening levels were considered to be of potential concern, and were assigned an approximate level of importance based on occurrence. A high-priority group included residual chlorine, methylene chloride, toluene, arsenic, cadmium, chromium, copper, lead, mercury, nickel, selenium, silver, zinc, chlordane, p,p'-DDE, dieldrin, gamma-BHC (lindane), total PCBs, and cyanide. A medium-priority group consisted of non-ionized ammonia, para-chloro-meta cresol, phenol, and diazinon. A low priority group was composed of phenolics recoverable, chloroform, antimony, thallium, bis(2-ethylhexyl) phthalate, diethyl phthalate, and di-n-butyl phthalate."