Mitigating Environmental Impact of Suburban Sprawl

Increasing suburban development and population density is a significant contributing factor to the impaired water resources in the Chesapeake Bay Watershed. Its impact is often hidden in the numbers because agricultural land represents almost twice the land as the developed areas. Growing populations in the suburban fringes of the Washington Metropolitan Area have had a significant impact on ecosystems in the region. Sprawling, low-density residential and commercial areas in the suburban and semi-rural areas result in additional infrastructure like roads (the controversial Bi-County Parkway) and shopping centers that chew up forests, green corridors, tree canopy, and agricultural lands. Often the remaining open areas between existing centers eventually fill with more new development. This type of development increases stormwater pollution and degrades the health of our water.

Image from Chesapeake Bay Foundation

According to the U. S. Environment al Protection Agency (EPA), the primary pollutants in the Chesapeake Bay and its tributaries are; nitrogen, phosphorus and sediment. These nutrients can lead to harmful algae blooms that kill underwater plants and destroy the river, bay and estuary habitat that aquatic life needs to survive. Excess nutrients and sediments can also lead to water with little or no dissolved oxygen to the detriment of aquatic life and the ecosystem. The Chesapeake Bay serves as a nursery ground for the fish and shellfish industry and protects the coast from storm surges and filters pollution. The estuary filters water that is carrying nutrients and contaminants from the surrounding watershed, protecting and restoring our drinking water supplies, the commercial oyster harvest and the beauty and ecological balance of the largest estuary in the United States.

EPA has legal authority to regulate point source releases of contaminants and pollutants- wastewater, industrial, and municipal separate stormwater systems (MS4), and concentrated animal feeding operation permits as well as set total maximum daily load (TMDL) of those contaminants in rivers and surface waters. The Chesapeake Bay pollution diet, the Total Maximum Daily Load (TMDL) of nitrogen, phosphorus and sediment was mandated by the EPA to the six Chesapeake Bay Watershed states (Virginia, Maryland, Delaware, New York, Pennsylvania and West Virginia) and the District of the Columbia.

EPA is invoking a “moderate levels of back stops” for Virginia under the Watershed Implementation Plan (WIP) for the TMDL to ensure adequate reduction in nutrient pollution to the Chesapeake Bay. This means that the WIP aggregate point source allocations for storm water and animal agriculture (CAFO) sectors were adjusted by the federal government to levels determined to be adequate to meet the TMDL. More stringent waste load allocations were applied to waste water treatment plants (regulated via federal programs); so that the waste stream from wastewater treatment plants was assigned to be 4 mg/L total nitrogen and 0.3 mg/L total phosphorus. For municipal separate storm sewer systems, MS4s, the federal government has imposed the requirement that 75% of urban MS4 lands meet aggressive performance standard through retrofit and redevelopment. I’m, quite frankly, not sure what that means in terms of installation and operation of storm systems, but the recent merger of the Virginia Department of Conservation and Recreation to have the Department of Environmental Quality (DEQ) be the lead agency for stormwater management is intended in part to address this.

In order to reduce the stormwater runoff carrying nitrogen, phosphorus, sediment and other pollutants from existing suburban residential areas stormwater best management practices (BMPs) will need to be implemented in the suburban communities. DNR, DEQ and the counties and cities of Virginia are going to have to implement non-point source nutrient management throughout the watershed. Homeowner Associations and individual homeowners need to individually and as a group reduce the nutrients and sediment run off from their properties.

Nutrient management and soil and water conservation districts (SWCDs) play a pivotal role in preventing such runoff in the agricultural community. In fact, SWCDs have been in the business of fighting erosion which prevents nutrient and sediment pollution since the mid-1930s, but agricultural operations are businesses that can see the direct result of maintaining their top soil and that have learned over the years to deal with various regulations. The challenge is much greater for the individual homeowner and the disperse sources of non-point source contamination; septic systems, poor drainage, impervious ground cover, lawn and plant fertilization, and household behaviors.

Virginia's 47 soil and water conservation districts have for years focused mainly on on-the-ground work implementing best management practices (BMPs) on farms. They have used the agricultural cost share program as the carrot to help foster the acceptance of BMPs and now have 100% funding available for their livestock exclusion program. DCR and the counties and conservation districts are attempting to develop strategies to reach out to not only farmers, but also urban and suburban landowners, and other land managers to encourage and help them to reduce their stormwater runoff and nutrient loads. Controlling runoff pollution is everyone's business and education and community have to be a large part of implementation. Each of us causes runoff pollution, and each of us must act to reduce its effects.

The difficult question is how does one educate the public of their responsibilities and then ensure that the public meets them? Suburban and semi-rural BMPs have the potential to significantly reduce nutrient and sediment pollution in the Chesapeake Bay, but DCR, DEQ and the Virginia Department of Health (VDH) have struggled to reach, educate and motivate the public. The VDH has set up an advisory committee of private sector septic design, maintenance and installation companies to assist in the transition to privatize the industry to the greatest extent possible and increase compliance with septic regulations by the public. Loudoun County has been in the forefront of innovative programs and to reach the public and appears to have successfully managed to privatize septic design, installation, maintenance and inspection within the county while utilizing their resources to track compliance.

Another area where Loudoun County is leading is experimenting with suburban BMP implementation programs. Loudoun County funded a pilot program with the county Soil and Water Conservation District to implement non-agricultural stream buffer plantings in several suburban developments. The Conservation district worked with county staff, the Department of Forestry, HOAs, individual homeowners, and all other stakeholders to plant canopy trees and under story plantings along stream banks to reduce erosion of the stream bank. The county provided funding for the pilot project at $7,000 per acre for a total of 10 acres the HOAs provided labor for the plantings and a covenant to maintain the plantings in perpetuity. The model of conservation districts working with suburban HOAs (especially the semi-rural developments) is one that could be copied and implemented broadly to include not only buffer plantings but infiltration trenches, bio-retention areas, rain gardens and curb cuts, dry swales and even septic maintenance best practices.

2013 Dead Zone

The NOAA-funded forecast, for the Chesapeake Bay, calls for a smaller than average dead zone in the nation's largest estuary this summer. Professor Bill Dennis of the University of Maryland Center for Environmental Science attributes this smaller dead zone to the cool and relatively dry spring followed by late arriving rains. The spring load of nutrients into the bay was light and locked in a lighter load of nutrients in the water layers within the Chesapeake Bay for the summer. The forecast is based to a large extent on the quantity and timing of rainfall in the Chesapeake Bay watershed, but the overall health of the Chesapeake Bay is also a contributing factor. So, there is hope that this forecast also reflects that the overall condition of the bay may be improving.

Dead zones have become a yearly occurrence in the Chesapeake Bay and other estuaries. Dead zones form in summers when higher temperatures reduce the oxygen holding capacity of the water, the air is still and especially in years of heavy rains that carry excess nutrient pollution from cities and farms. The excess nutrient pollution combined with mild weather encourages the explosive growth of phytoplankton, which is a single-celled algae. While the phytoplankton produces oxygen during photosynthesis, when there is excessive growth of algae the light is chocked out and the algae die and fall from the warmer fresh water into the colder sea water. The phytoplankton is decomposed by bacteria, which consumes the already depleted oxygen in the lower salt level, leaving dead oysters, clams, fish and crabs in their wake.

In a wedge estuary such as Chesapeake Bay where the layers of fresh and salt water are not well mixed, there are several sources of dissolved oxygen. The most important is the atmosphere. At sea level, air contains about 21% oxygen, while the Bay’s waters contain only a small fraction of a percent. This large difference between the amount of oxygen results in oxygen naturally dissolving into the water. This process is further enhanced by the wind, which mixes the surface of the water. Scientists are still studying the impact of the winds in delivering oxygen to various water layers. The other important sources of oxygen in the water are phytoplankton and aquatic grasses which produce oxygen during photosynthesis, but when they die consume oxygen during decomposition by bacteria. Finally, dissolved oxygen flows into the Bay with the water coming from streams, rivers, and the Atlantic Ocean.

From USGS

Stream flow into the Chesapeake Bay is currently at “normal” levels after a relatively dry early spring. Overall, data from the U.S. Geological Survey, USGS, shows that the dry years of 2000-2004 are behind us and we may be entering a wet period. The Chesapeake Bay Program in partnership with USGS, monitors stream flow, nutrients and sediment in the rivers throughout the Chesapeake Bay watershed. There are 85 sites in the network; currently being monitored; however, only 31 of these sites have enough long-term data to be used to forecast trends. In the mid-1980s, the Chesapeake Bay Program (CBP), a partnership between the Commonwealths of Pennsylvania and Virginia, the State of Maryland, the District of Columbia, the Federal Government, and the Chesapeake Bay Commission, began efforts to reduce nutrients and sediments in the bay. Improvement in water-quality conditions in the bay has been slower than promised; however, and the U.S. Environmental Protection Agency, EPA, stepped in to put the entire region on a pollution diet. The Chesapeake Bay pollution diet, the Total Maximum Daily Load (TMDL) was mandated by the EPA to the six Chesapeake Bay Watershed states and the District of the Columbia. TMDLs for nitrogen, phosphorus and sediment were assigned by the EPA to each segment of the Chesapeake Bay Watershed in all six Chesapeake Bay watershed states.

Dead zones have become common summer events caused by man, human waste, and the waste and excess nutrients from agriculture necessary to feed us and ornamental gardens to please us. It has be predicted by Researchers from Texas A&M University that the Gulf of Mexico dead zone currently estimated at 3,300 square miles will exceed the typical summer average of 5,600 square miles. The scientists are predicting more than 9,400 square miles of dead zone in the coastal waters of the estuary due to the heavy rains in the upper  Mississippi that flooded fields and towns during the spring carrying with the flood waters the excess nutrients from farms, yards, septic systems and sewage treatment plants in its wake. The Gulf of Mexico Dead Zone is not expected to peak until late August.

From IAN UMCES source of nitrogen pollution in Chesapeake

The Future of Lawn Care in Virginia

About half of the land area of Virginia is drained by the creeks, streams and rivers that comprise the Chesapeake Bay watershed, and two-thirds of the state's population lives within the watershed. From the Shenandoah Valley to the Eastern Shore, each Virginian can literally touch the Chesapeake Bay through the network of creeks and streams that cover the area. In an effort to reduce pollution in urban and suburban runoff one of the growing areas of nutrient pollution in the Chesapeake Bay estuary, the 2011 Virginia General Assembly passed SB 1831 that bans phosphorus in most lawn fertilizers and more tightly restricts the use of fertilizer by professional lawn and turf service companies. This bill was supported by the Chesapeake Bay Foundation and the Piedmont Environmental Counsel.

The newly passed law prohibits the sale, distribution and use of lawn maintenance fertilizer containing phosphorus after December 31, 2013 and it will be unlawful to offer for sale any deicing agent containing urea, nitrogen, or phosphorus intended for application on parking lots roadways, and sidewalks, or other paved surfaces. The law also requires golf courses to implement nutrient management plans by July 1, 2017, and will utilize the existing resources of the Soil and Water Conservation Districts and the Department of Conservation and Recreations to provide technical assistance and training and establish a cost-share program to assist in implementation of the nutrient management plans. For homeowners the Department of Agriculture and Consumer Services will develop consumer information and recommended best practices for the application of lawn fertilizer. The law also regulates lawn service companies and establishers reporting requirements for those who apply lawn fertilizer to more than 100 acres of nonagricultural lands annually This effectively leverages the existing resources and expertise to get the most bang for the buck in meeting the Chesapeake Bay TMDL and restoring the Chesapeake Bay estuary and should not impact property owners excessively. Research has shown that most lawns are not deficient in phosphorus and phosphorus free lawn fertilizer is widely available.

The TMDLs were created by a series of models of the Chesapeake Bay Watershed that include various land use models, water quality models and watershed models. These computer models are mathematical representations of the real world that estimate environmental events and conditions. The models are at best imperfect, but they are nonetheless the best tool available to view the 64,000 square miles of the watershed. The Chesapeake Bay and its watershed are so large and complex, that scientists and regulators rely on computer models for critical information about the ecosystem’s characteristics and the impact of various environmental actions to reduce pollution.

Pollutions loads for nitrogen, phosphorus and sediment in the urban areas are calculated using a constant pounds/acre/year for impervious acres as a fixed input, and the pervious load is based on total fertilizer sales data. Reducing the salting of roads, sidewalks and parking lots should impact the load number on impervious acres. Restricting the statewide sales of phosphorus containing fertilizer will reduce the total sales number which represents roughly five percent of excess nitrogen and phosphorus pollution discharged into the Chesapeake Bay from Virginia.

Most lawns are not deficient in phosphorus. Despite the widely accepted myth that phosphate fertilizers will stimulate root growth of transplanted trees and shrubs, research at Washington University has proved this incorrect. Only soils that have been heavily used for agricultural crops or are acid sandy and granitic soils tend to have their phosphorus depleted. In landscaped urban soils, phosphorus is rarely deficient and the misapplication of this element can have negative impacts on the soil environment and the watershed without any benefit to the lawn or plants. Restricting the statewide sale of lawn fertilizer containing phosphorus and educating homeowners about the inappropriate use of lawn fertilizers is a simple way to reduce nitrogen and phosphorus runoff and save consumers a few dollars on unnecessary fertilizer. This could prevent the EPA from implementing stricter stormwater point source limits which was one of “backstop” threats leveled at Virginia if we fail to meet the Chesapeake Bay TMDL goals. This simple step should be all the more effective when the suburban/urban surface portion of the Chesapeake Bay model is revised.

Phosphorus in the Chesapeake Bay

Phosphorus is essential for plant growth, but soils in Virginia are naturally low in phosphorus. Virginia soils require supplemental phosphorus to maximize crop yields and so are a necessary agricultural fertilizer. Phosphorus enters to Chesapeake Bay watershed from the actions of man. Farming and agricultural activities are often seen as the only source of phosphorus, but that is not true. Phosphorus is a naturally occurring element that is naturally found in rock, soil, water and all living organisms. Of the estimated 17 million pounds of phosphorus entering the watershed, it was estimated in 2009 that about 8.3 million pound of phosphorus was from agriculture and 6.5 million pounds was from waste water treatment plants and urban runoff from predominately pervious surfaces (lawns). The growing suburban/urban population is a serious contributor to contamination. However, concentrated poultry feed operations are significant sources of excess phosphorus.

To give you some perspective on the quantities of phosphorus generated in sewage, according to the Delaware Department of Natural Resources and Environmental Control, the typical household generates 1-2 pounds of phosphorus per year and there are approximately 4.5 million households in the Chesapeake Bay watershed, representing 4.5-9 million pounds of potential phosphorus contamination (without the use of phosphorus removing technology at waste water treatment plants). According to a Maryland state study, each chicken generates approximately 0.35 pounds of phosphorus per year. Animal guano is a much bigger source of phosphorus than human waste, but the growing volume of households can create a problem that grows over the years.

The phosphate rock in its commercially available form is called apatite which is merely calcium phosphate. Other deposits may be from fossilized bone (animal or human) or guano (poultry waste). When plant materials and waste products decay through bacterial action, the phosphate is released and returned to the environment for reuse. Weathering and erosion of rocks and bones gradually releases phosphorus as phosphate ions which are soluble in water. A large percentage of the phosphate in water is precipitated from the water as iron phosphate which is insoluble. If the phosphate is in shallow sediments (wetlands), it may be readily recycled back into the water for further reuse. In deeper sediments in water, it is available for use only as part of a general uplifting of rock formations.

Most of the phosphate Chesapeake Bay watershed enters the water through the water run-off and release from waste treatment plants. Over application of phosphorus is caused by the use of manure from the concentrated poultry feed operations. Poultry typically has nearly equal concentrations of phosphorus and nitrogen, though crops typically require 2.4-4.5 times the nitrogen as phosphorus. Pig manure has slightly more nitrogen than phosphorus. Cow manure has typically twice the nitrogen as phosphorus and is much less of a problem. Historically, manure has been added to obtain the correct nitrogen content not the lower phosphorus needs. The excess phosphorus is released through leaching, runoff and erosion.

As for waste treatment plans without an expensive tertiary treatment, the phosphate in sewage is not removed during treatment. So what happens in the release areas from waste water treatment plants is that the phosphate sediment (iron phosphate) builds up over time. Lower the concentration in the waste stream and phosphorus is released from the sediment. As removal technology has improved for nitrates and phosphorus, waste treatment plants have had to exercise careful balancing act to control the algae blooms. I can find no studies of impact from release from single family septic systems and this may be due to the low concentration and plant uptake and mineralization.

Phosphorus can be found dissolved in the soil solutions in very low amounts or associated with soil minerals or organic materials. The relative amounts of each form of phosphorus vary greatly among soils, with the total amount of phosphorus in a clayey-textured soil being up to ten times greater than in a sandy soil. (University of Arkansas). Organic phosphorus in soils is made up of a large number of compounds, with the majority being of microbial origin. Organic phosphorus is held very tightly and is generally not available for plant uptake until the organic materials are decomposed and the phosphorus released via the mineralization process. Mineralization is carried out by microbes, and the rate of phosphorus release is affected by factors such as soil moisture, composition of the organic material, oxygen concentration and pH.

The reverse process, immobilization, refers to the tie-up of plant-available phosphorus by soil minerals and microbes that use phosphorus for their own nutritional needs. Microbes may compete with plants for phosphorus, if the decomposing organic materials are high in carbon and low in nitrogen and phosphorus. Mineralization and immobilization occur simultaneously in soil. If the phosphorus content of the organic material is high enough to fulfill the requirements of the microbial population, then mineralization will be the dominant process.

Most of the phosphorus added to soil as fertilizer and manure is rapidly bound by the soil minerals to the inorganic form and is not subject to rapid release. Thus, soil solution phosphorus concentrations typically remain very low, the concentration of inorganic phosphorus (orthophosphates) in the soil solution at any given time is very small, amounting to less than 1 lb/Acre. Phosphorus in the inorganic form occurs mostly as aluminum, iron or calcium compounds. This series of reactions is commonly referred to as sorption or fixation. Iron and aluminum compounds will fix (tie-up) phosphorus under acidic conditions (soil pH <= 7), phosphorus is preferentially fixed by calcium and magnesium compounds. Phosphorus availability to plants in most soils is greatest when soil pH is in the range of 6 to 7. Hard water is particularly high in calcium compounds, iron and magnesium which allows the mineralization and why septic systems may be able to handle the limited amount of phosphorus released by the typical human household each year.