|
|
| 5. SUMMARY |
|
The following conclusions are derived from this study:
Sand originating in the mountains of the Sierra Juarez is being deposited in El Barbon Wash, in the vicinity of the valley of Real del Castillo Viejo, in Baja California. Normal geologic accretion in this region is attributed to the valley slope (0.005) being much smaller than the mountain slope (0.030). The deposited sand fills the channel and creates a flood hazard to local property owners (ejidatarios). The deposited sand in high-quality construction-grade material and, therefore, marketable to potential customers elsewhere. Current environmental regulations in the United States have effectively discouraged sand-mining operators from continuing to mine streambeds in Southern California. In the meantime, the cost of sand has nearly doubled, setting the stage for import. In the past 6 years, the percentage of sand used in San Diego County and originating in Baja California has increased steadily, from close to zero to nearly 40% at present. El Barbon Wash has been sand-mined for about two years. The total volume of extraction to date (July 2002) is about 1 million m3; and mining continues. The operator has a permit to extract 7.6 million cubic meters of sand in a 10-km stream reach. The extracted material is being transported by trucks to Ensenada, where it is shipped in barges to destinations in Southern California. The sand is being used mostly as an aggregate for cement and asphaltic concrete. Sediment routing computations show that the amount of sand that is likely to be deposited in a 13.5-km reach, overlapping the current permitted reach, is 5.5 million cubic meters in a period of 50 years. Properly executed, sand mining will reduce flood hazard to local property owners (ejidatarios). Properly executed, sand mining will have moderate environmental impacts, including impacts to groundwater, riparian habitat, noise and dust pollution, and landscape aesthetics. The socio-economic impacts of sand mining in El Barbon Wash are expected to be substantial. Issues yet-to-be-resolved in a satisfactory manner include the right of passage through private property, the effect on the local sand market and the local economy, and the effect on the transportation infrastructure.
National emergent regulations for sand mining are currently being considered by the Mexican government. These regulations would require the maintenance of an undisturbed layer of a certain minimum thickness in the streambed, ostensibly for the protection of the aquifer. Enaction of this regulation should be followed by measurements in El Barbon Wash to verify compliance.
|
| Impacts of Sand Mining | Management | Regulation of Sand Mining in the U.S. | Strategies for the Ojos Negros Valley | Sand Mining Facts |
| http://ponce.sdsu.edu/protected2/sandminingfacts05.html | 020714 |