Northumberland County has been informed that the existing County Code does not conform to the Bay Act. The Planning Commission and the Board of Supervisors must rectify this situation before the end of the year, or else face legal action. Two major changes must be incorporated into the County Code. Absolute enforcement of the 100 foot Resource Protection Area (RPA) is mandated, although an “administrative process” can provide relief outside the 50 foot boundary in the case of properties platted before Oct. 1, 1989. Absolutely no construction will be permitted within 50 feet of the water no exceptions. After adoption, no tree larger than 3 inches in diameter at chest height can be removed from the RPA without explicit permission. Mandatory septic system inspection is also imposed.
Why is the County being required to adhere to the Bay Act? Simply stated, to stop, and hopefully reverse, the decline in water quality in our waterways and Chesapeake Bay in the face of a growing population. The primary goal of a RPA and of mandatory septic system maintenance is the same to reduce the amount of nitrate and phosphate that enter the water.
It must be clearly understood that almost all the nitrate and phosphate that enter our waterways do so via the groundwater. Runoff, or the flow of water over the land surface and into the water is rare in our sandy soils unless the plant cover at the land surface has been compromised. We receive approximately 42 inches of rain each year, about 2/3 of which evaporates or is transpired by plants. The remainder, a little over a foot of water, infiltrates the soil and percolates down to the water table, or the level to which water rises in an open hole. The water table is almost always above sea level, and as a result, groundwater is always in motion, flowing “downhill” through the ground toward the nearest water body. Over long time intervals a “steady state” exists in which infiltration (a bit more than one foot of water each year) equals discharge to the waterways. The amount of water involved is immense, amounting to about 660,000 gallons of water each day for every square mile of the Northern Neck (here’s the math 42/12 * 1/3 * 5280 * 5280 * 7.48 / 365). As the rain infiltrates the soil and flows through the shallow unconfined aquifer to the waterway, it dissolves substances like fertilizer and incorporates the discharge from septic systems.
On average, our shallow groundwater contains about as much nitrate as the effluent from a state-of-the-art sewage treatment plant, about 4 mg/l (milligrams per liter or parts per million). If you want a vivid picture of the problem, imagine 3 Reedville-sized sewage treatment plants installed on every square mile of the Northern Neck. Assume they are state-of-the-art plants, each discharging 200,000 gallons of water containing 4-mg/l nitrate each day. You are now imagining the magnitude of the problem.
If we want to clean up the water in our local waterways, we must reduce the input of nitrate and phosphate to the waterways. We can do this by reducing the amount of nitrate and phosphate that is added to the groundwater, and/or we can try to remove the nitrate and phosphate already in the groundwater before the water discharges into the waterway. A 100-foot RPA containing deep-rooted trees is the best way we know to “sop up” the nutrients already in the groundwater. The process is not perfect, but it is certainly the least expensive available solution. Large trees are absolutely critical in the RPA because they have a large root network that extends down to, and in cases slightly below, the water table. The nitrate and phosphate are removed by the tree and by microbial reactions within the root zone. Assuming a large tree has a canopy (and supporting root zone) about 50 feet in diameter, it is clear why a 100-foot of buffer is required. Staggered trees two-deep is much more efficient that a single line of trees. The worst possible land use next to the water is a chemically maintained lawn and a hardened shoreline. The absence of trees and marsh grass ensures that all the excess chemicals from the lawn and the septic system discharge directly into the creek via the groundwater.
Reducing the amounts of nitrate and phosphate that enter the groundwater is also important. Fertilizer should be used sparingly, remembering that rain supplies about 5 pounds of nitrogen per acre each year courtesy of all the combustion of fossil fuels that drives our life style. Farmers should use Best Management Practices, especially nutrient management plans for both nitrate and phosphate. We all should minimize the solids and water that enter our septic systems (do not use a garbage grinder compost kitchen waste instead). It remains to be seen the exact wording the Board of Supervisors will adopt, but a reasonable regulation would require everyone to have their septic system inspected every 5 years and the tank pumped if it contains more than about 20% solids (sludge).
We all contribute nitrate and phosphate to the groundwater. We all need to make changes in our life style to have any hope of improving the water quality in our local waterways. We all need to understand how our septic systems function, and how they need to be maintained. We all need to grow large trees between the septic system (but never shading the drain-field) and the nearest water. We all need to minimize the use of fertilizer. We all need to refrain from disposing of any kind of organic matter (or anything else for that matter) in our waterways. The modifications to the County Code we are being required to adopt, if enforced, are intended to improve water quality. Improved water quality should be an explicit goal for us all, and should take precedence over any personal motives we each might have.