Monday, August 9, 2010

Chesapeake Bay Watershed and Backyard Chickens

On July 8th 2010 the Prince William Planning Commission held public hearings on a proposed change to the zoning and land use regulations within the county. Currently chickens and other farm animals are allowed on 2 acres or more of agricultural land, but only if there's no house on the land. If there's a house, the property is considered residential and chickens are not allowed. Though probably not intended this regulation serves to protect the groundwater of the county. The proposed change to the zoning law would allow up to 10 chickens, pigeons or doves, or 5 ducks, or 3 turkeys, geese or pea fowl, or one emu or ostrich, or some combination of those on 2 acres. The law would also require the birds to be kept in a fenced area, coop or cage at least 10 feet from the house on the property, and at least 15 feet from the property line. The Planning Commission has tabled the matter.

According to Rodale's All-New Encyclopedia of Organic Gardening, poultry manure (chicken in particular) is the richest animal manure in nitrogen (N), phosphoric acid (P) and potash (K). Chicken manure is considered "hot" and must be composted before adding it to the garden. Otherwise, it will burn any plants it comes in contact with. However, there is an even darker side to poultry manure. The main cause of the Chesapeake Bay's poor water quality and aquatic habitat loss is elevated levels of two of those nutrients, nitrogen and phosphorous. According to the Chesapeake Bay foundation, runoff from animal manure accounts for about one-quarter of the nitrogen and phosphorus pollution that feed "dead zones" downstream.

According to the Virginia Cooperative Extension, poultry yards, and enclosed holding areas are areas of concentrated and accumulated animal wastes. These areas can be a source of nitrate and bacteria contamination to groundwater. The impacts can be mitigated by utilization of farm best management practices (BMPs); however, backyard farmers are not often versed in appropriate waste management techniques. The potential for livestock and poultry operations to affect groundwater is greatest if located on Karst terrain or over sandy-textured permeable soils, or other susceptible groundwater basins.
According to the US Geological Survey (USGS), much of Prince William County, especially the northeastern portion is located within the Culpeper basin which is highly susceptible to contamination. This is the source of drinking water for all the private wells in the area and feeds the tributaries to Bull Run.

The geology of this area consists of an interbedded sequence of sedimentary and basaltic rocks. The rocks of the Culpeper basin are highly fractured and overlain by a thin cover of overburden (that would be soil). The lack of overburden is a challenge to gardens and limits natural protection to the aquifer. The sedimentary rocks create a productive aquifers, but allow contaminate to easily wash into the groundwater basin. Ground water flows under ambient pressure from Bull Run Mountain towards Bull Run, the river. The soils in this area are described by the USGS as Balls Bluff Siltstone with a gravel, sand and clay type bedding plane. (That is the technical name for the flat plane, edged orange red rocks that are everywhere you put a shovel.) In the siltstone bedding plane, the fractures within the rock run predominately north south. Thus while ground water flows generally speaking west to east, water or a contaminant that catches a fracture will carry the contaminant to drinking water depth in a north south pattern. Contaminants can enter the groundwater at these fractures and zigzag through the adjacent neighborhoods.

There are two risks that should be carefully considered by the Planning Commission when making this decision, potential contamination of the drinking water supply for the area and potential for contaminated runoff to impact the Chesapeake Bay. Runoff from animal manure accounts for about one-quarter of the nitrogen and phosphorus pollution that feed "dead zones" downstream. Over the past few years, as I have monitored my groundwater quality, I have watched the nitrogen levels in my neighborhood rise. Groundwater protection should be a major consideration in whether to allow poultry on all residential properties. As our area has become more suburban, density has increased, along with the utilization of groundwater for domestic purposes and the density of septic systems. Unless, they intend to regulate the micro poultry farms and require the implementation of and maintenance of BMPs to manage the waste the county Planning Commission should deny the request.

1 comment:

  1. how is having backyard chickens any worse than all the fertilizer that is applied to suburban lawns. Perhaps we should have an ordinance on the use of fertilizer instead...

    I believe the data you are referencing largely comes from industrial agriculture production, where there is so much chicken manure that they cannot process it all with having it runoff into the rivers and streams. localizing our chickens to our own backyards can only help solve this problem, not add to it!