san diego nine months president donald trump take office first tangible sign progress one central promise campaign appear along u.s. border mexico couple miles km bustle otay mesa border cross san diego eight tower chunk concrete steel stand high 30 feet meter tall sky possible model trump promise one day solid wall extend full length southern border california texas whether eight different prototypes construct last month become part actual wall remain highly uncertain u.s. congress far show little interest appropriate estimate 21.6 billion would cost build wall still border patrol officials monday welcome momentum trump pledge generate groundswell voter support help elect office current infrastructure well two decades old roy villareal deputy chief patrol agent u.s. border patrol san diego sector say tour media organizations monday morning need improvement absolutely currently 654 miles 1,052 km 1,900-mile 3,058-km border mexico fence single double triple fence second line fence san diego 18 feet 5.50 tall breach nearly 2,000 time last three years villareal say even trump wall never get fund villareal say border patrol might incorporate one new wall design replace wear section exist fence six contractors across country select build eight prototypes complete week builders pay attention aesthetics bid win lucrative contract one wall segment feature deep-blue steel another brick facade stand sharp contrast area exist border fence ramshackle structure corrugate steel leave vietnam war late november private company border patrol officials decline name begin 30- 60-day process test wall prototypes determine easy would climb dig beneath final selection could combination prototype design villareal say solid concrete wall daunt presence might adverse effect border patrol activities since agents would able see potential crossers approach wall much size wall ability see whether 10 people 30 people ... rifle say rowdy adams former border patrol agent leave agency 2011 30 years important see set response plan place two eight prototypes see-through design environmentalists warn solid wall would prevent wildlife include dwindle population federally protect ocelots cross concrete wall may also prove challenge build without participation world large concrete suppliers mexico cemex switzerland lafargeholcim tell reuters participate project associate wall border wall prototypes first small step trump campaign promise