| Business | Phone |
| Brian C Regan Engineering 1811 Rock Springs Rd, San Marcos 92069 | (760) 431-6863 |
| Engineering Design Group 2121 Montiel Rd, San Marcos 92069 | (760) 839-7302 |
| Piro Engineering 930 Boardwalk # D, San Marcos 92078 | (760) 744-3700 |
| Daniel P Cole Engineering 1655 Via Del Corvo, San Marcos 92078 | (760) 744-1323 |
| Helming Engineering Inc 1650 Linda Vista Dr # 202, San Marcos 92078 | (760) 744-9801 |
| Keith Companies Inc 277 Rancheros Dr # 300, San Marcos 92069 | (760) 438-1210 |