Dairy Herds and Rural Communities in Southern New Mexico
Arnold, Stephen D., Journal of Environmental Health
This paper is the first in a two-part series about the environmental health impact that dairies have on local communities. Part I focuses on health concerns that result from groundwater contamination, odor, flies, and dust. Part II, to be published in the September 1999 issue of the Journal, will address the specific problem of groundwater contamination from nearby dairy feedlots and wastewater lagoons.
New Mexico has the fifth-largest land area among U.S. states and has a low population density of 12.4 persons per square mile. Between 1990 and 1995, New Mexico was the seventh-fastest-growing state. The population reached 1.6 million in 1995, which placed the state 36th in total population and sixth lowest in population density (1). With 13,500 farms covering 43.7 million acres, as well as 22.2 million acres of Bureau of Land Management (BLM) and Forest Service land that is leased to farmers and ranchers, New Mexico has a significant agricultural sector. New Mexico livestock agriculture consists of 8,500 cattle ranches, 700 milk cow farms, 1,000 sheep ranches, and 500 hog farms (2). In amount of milk produced, New Mexico ranks 12th among U.S. states. Growth of the dairy industry has been spectacular in the last two decades, especially in southern New Mexico. In 1970, milk production totaled 304 million pounds. By 1995 it had soared to 3,623 million pounds (3).
A concern is nitrate contamination of groundwater from unlined, manure-lined, or clay-lined holding lagoons used for the disposal of dairy wastes. Many New Mexico milking operations are located in an established dairy center, termed "the dairy belt," along the Rio Grande River to the north and south of Las Cruces in Sierra and Dona Ana counties. The dairy belt presents a special concern because
* the depth to groundwater in the alluvial aquifers in the Rio Grande Valley is unusually shallow;
* the alluvial materials are generally permeable and allow relatively rapid movement of contaminants from the surface to underlying aquifers; and
* the domestic water supply relies on alluvial groundwater (4).
Pursuant to section 3-104 of the New Mexico Water Quality Control Commission (WQCC) Regulations, all dairies in New Mexico are required to apply for and maintain a groundwater discharge permit for discharge of wastewater generated from milk production activities (5). Wastewater must be handled in accordance with the approved permit, which specifies whether wastewater must remain onsite or discharge to neighboring agricultural land is allowed. Discharge to an existing waterway is not allowed.
New Mexico dairy farmers are working with state agencies to develop guidelines that allow a dairy farmer to submit a single discharge plan. This is a new effort, and guidelines are not yet finalized. This single discharge plan must comply with the technical discharge plan requirements of the WQCC regulations, the requirements of the National Pollutant Discharge Elimination System General Permit for Concentrated Animal Feeding Operations (CAFO), the New Mexico Environment Department Policy for Storage and Disposal of Dairy Wastes, and the Water Quality Act (6). A number of resources are available to assist dairy owners in complying with state and federal regulations that govern milk quality and disposal of wastewater. The Cooperative Extension Service at New Mexico State University has developed a detailed on-line series of fact sheets called Farm*A*Syst, constituting a voluntary groundwater protection program for New Mexico farms, ranches, and rural homeowners (7). Numerous national resources also are available on line.
In addition to groundwater contamination, other health concerns for rural populations surrounding dairy farms include odor, flies, and dust. Odors from concentrated animal-feeding operations can be extremely displeasing to area residents; dust is a nuisance and a potential health hazard. …