FIRST DRAFT
Report on Creation of an Occoquan Reservoir Protection Overlay District
MIDCO, October, 2011
Report on Creation of an Occoquan Reservoir Protection Overlay District
MIDCO, October, 2011
Background
In December, 2010, the Prince William County Board of Supervisors adopted a revised version of the Environment Chapter of the County Comprehensive Plan. This revised document contains the following Policy:
EN9.1 Amend the Zoning Ordinance to develop a Drinking Water Reservoir Protection Overlay District to protect the quantity and quality of public drinking water supplies, to include the following:
Minimum setbacks from reservoirs.
Minimum setbacks for the installation of septic fields, tanks or other on-site subsurface sewage disposal systems from the shoreline of reservoirs.
Enhanced erosion and sediment control measures.
In April, 2011, MIDCO President Martin Jeter appointed a committee to help move the overlay district idea from a concept to formal language in the Zoning Ordinance. The committee met monthly, usually with an expert resource person in attendance, in order to develop this report.
Committee Objectives
The committee developed the following objectives:
1. Obtain a good understanding of the water quality and quantity problems in the Occoquan Reservoir;
2. Obtain a good understanding of current and pending efforts to protect the quality of water in the Occoquan Reservoir;
3. Identify areas of study that would better define the problems and solutions;
4. Set forth goals for the proposed ordinance;
5. Set forth potential elements of an Occoquan Reservoir Protection Overlay District;
6. Set forth suggestions for voluntary actions by residents of the overlay district to supplement the contents of a reservoir protection overlay district.
Water Quality in the Occoquan Reservoir
The Occoquan Reservoir has been the subject of study for many years. During the 1960’s and 1970’s, the focus of concern was the impact on water quality of poorly treated sewage effluent being discharged into the Occoquan watershed and flowing into the reservoir. This resulted in the development of the Occoquan Policy, which required the elimination of multiple sewage treatment plants and the construction of a regional high-performance treatment plant administered by the Upper Occoquan Sewage Authority.
These activities cost many millions of dollars and represented the idea that the Occoquan watershed and the Occoquan Reservoir in particular were considered major sources of drinking water for Prince William County and much of Northern Virginia for many years to come. These investments have been notably successful in significantly reducing the levels of pollutants in the Occoquan Reservoir. So much so, in fact, that during low flow conditions, when the effluent from the USOA treatment plant constitutes a higher than normal percentage of water in the reservoir, the level of pollutants in the reservoir is lower than at other times.
Over the years since the adoption of the Occoquan Policy, total investment in sewage treatment facilities in the Occoquan Reservoir’s water shed has approached a billion dollars. This investment in sewage treatment could be rendered meaningless if pollutants in surface runoff and subsurface drainage into reservoir are not adequately removed.
The principal pollutants that the UOSA treatment plant successfully eliminates are also components of runoff from urban and rural land. These are nitrogen, phosphorus and suspended solids, or silt. In surface runoff, these pollutants are most commonly the result of land disturbance and soil erosion, but are also a result of fertilizer application, animal wastes, and low functioning individual sewage treatment systems (septic tanks). Other pollutants of concern in surface runoff include chemicals from petroleum products, medicines, pesticides and herbicides.
Silt entering the reservoir not only brings pollutants attached to it, it is a pollutant itself, which must be removed from the drinking water supply. Silt builds up on the bottom of the reservoir, reducing the reservoir’s capacity. While siltation is a natural process, it is vastly accelerated by our use of the land in both rural and urban areas. One only needs to see the reservoir after a heavy rain to observe the seriousness of this problem. Storm water management controls are only partially successful in controlling siltation of the reservoir. Some estimates are that the reservoir has lost a billion gallons of capacity due to siltation.
The Fairfax Water Authority (“Fairfax Water”) takes water out of the reservoir near the Town of Occoquan, treats it in an expensive new high-performance treatment facility, and distributes it throughout Northern Virginia. Use of the Occoquan Reservoir as a drinking water supply is going to continue and expand in the foreseeable future. While it is important to protect the reservoir’s storage capacity, it is expected that its capacity of _____________gallons will be supplemented by storage facilities that are currently stone quarries within the watershed. The source of water for these additional storage facilities will continue to be the Occoquan Watershed and the Occoquan Reservoir.
Control of Pollutants in Surface Runoff
Prince William County and other jurisdictions in the Occoquan watershed have instituted a variety of controls for reducing the amounts of pollutants in surface runoff. Driven largely by state and national environmental standards, these regulations have been expanded and made more effective during recent years, and they will continue to become more effective and more expensive. Most of these controls are applied to sites that are undergoing development. In more recent years, these controls have been extended to control pollutants from developed sites on an ongoing basis. While these control mechanisms are effective, they have not been adequate to reduce pollutant loads in the Occoquan Reservoir to acceptable levels. Continuing urbanization in the watershed will inevitably add more pollutants, despite improved controls on runoff.
Controlling pollutant levels in surface runoff involves a wide range of regulations and methods. Many of these regulations require structures such as storm water management ponds, settlement basins, and other constructed elements that capture pollutants. Other regulations apply to management of exposed soils and slopes. There are also regulations that rely on preserving undisturbed land to filter and reduce pollutant flows from development sites into streams, such as requirements for leaving wooded buffers along streams and limitations on construction on steep slopes. Primary among this type of regulation are density controls, which directly reduce the amount of land disturbance in an area. Finally, there are regulations that apply to on-going land uses, such as requirements for reducing pollutants in runoff from agricultural facilities, requirements for advanced individual sewage treatment systems and restrictions on use of fertilizers containing phosphorus.
Dealing with water pollution involves costs that we all must pay, one way or another. Most of the direct costs of new regulation will be imposed on the generators of that pollution. In the past, many generators of pollution did not pay these costs, because they externalized them, relying on someone else (or Mother Nature) to deal with some or all of the pollution they were causing. Although the direct costs of many of the new requirements to reduce pollutants in surface runoff will be imposed on the generators of the pollution, we all will pay as those new costs are passed on. In addition, the general public will be taxed to retrofit the inadequacies of developments built in the past. An Occoquan Reservoir Protection Overlay District should be designed so that the additional costs are minimized and the resulting reduction in pollution maximized.
A fair question here is whether it makes sense to place additional controls on development and on existing land uses in only a portion of the watershed, as opposed to making those controls apply to the entire watershed. While additional controls applied to the entire watershed might be desirable, there also appears to be a rationale for applying additional controls to an area adjacent to the reservoir and not applying them farther away. Distance plays a role in reducing pollutants contained in runoff. This cleansing effect, provided largely by Mother Nature, is well known. In addition, different control measures may be appropriate in areas closer to the reservoir than in more distant areas.
Areas of Further Study
Most of the experts who spoke with the committee indicated the need for additional studies and also described ongoing studies that relate to pollution concerns in the Occoquan Reservoir. Some jurisdictions have done studies to establish the importance of various sources of pollution in their waterways. This appears to be a helpful area of study for the Occoquan Watershed and Reservoir, because it would demonstrate the extent to which water pollution is caused by different types of activity, such as urban runoff, agricultural runoff, land development, sewage treatment plants, individual sewage disposal systems and deposition from the air.
The Committee also thought that it would be a good idea to establish some studies of water quality in selected sub-watersheds in the area proposed for the Overlay District, prior to enactment, so that pollution loading in these watersheds can be documented over time. The committee also discussed the issue of failing septic tank systems. The committee recommends that a study be made in the overlay district area of Individual sewage treatment systems in order to determine the extent of possible pollution from these systems, with recommendations as to what actions would be feasible to undertake to address the problems found.
Ground water supply in the watersheds leading directly to the Occoquan Reservoir is also a concern. Already, the Prince William Service Authority has indicated a preference for running a water line to the Occoquan Forest subdivision of some 250 homes, rather than continuing to rely on the community’s well supply. Another area of investigation is the question of fertilizers. New state law will reduce the amount of phosphorus in fertilizers, but would it be appropriate to prohibit the application of certain fertilizers within a reservoir protection overlay district?
Goals for an Occoquan Reservoir Protection Overlay District
The committee established the following goals for an overlay district:
1. Reduce the amounts of pollutants entering the reservoir from the land area included in the overlay district. This, of course, is the overriding goal – all other goals are contributory
2. Provide an area for the county to focus its efforts to measure the effectiveness of various methods for reducing the amount of pollutants entering the reservoir.
3. Provide an area in which to focus County efforts to deal more effectively with pollutants entering the reservoir from already developed urban areas, such as Lake Ridge.
4. Provide an area in which to focus county efforts to obtain voluntary cooperation among citizens and businesses in activities that would result in reduced pollutants in the reservoir.
5. Provide regulatory controls that will support the Comprehensive Plan and citizens views of development in the mid-county area near the Occoquan Reservoir.
6. Provide regulatory controls that are achievable and that entail costs that do not fall unfairly on any segment of the county’s economy.
Elements of an Occoquan Reservoir Protection Overlay District
The Committee did not attempt to write a zoning ordinance amendment. This task can be carried out far more appropriately by the County staff and Planning Commission. However, based upon the information that it has obtained, the committee has developed a list of potential elements for an Occoquan Reservoir Protection Overlay District, as follows:
1. The overlay district should extend one mile (or more) from the centerline of the Occoquan Reservoir, beginning at the dam near the Town of Occoquan and extending upstream to Route 234 on the Occoquan River and to the City of Manassas Park on Bull Run (See attached map). Some members of the Committee thought the overlay district should extend to the top of the watersheds that directly drain into the reservoir. The area within one mile of the reservoir covers a significant portion of the small watersheds that drain directly into the Occoquan Reservoir. The land included in this area is generally comprised of forested, rugged terrain with significant areas of 15 to 25 percent slopes, and includes small functioning wetlands. Much of the land area is developed on five-acre lots, but a significant area is within Lake Ridge and several other urban developments, which will provide the opportunity to develop regulations for reducing pollutants in runoff from existing urban development, improve storm water facilities and to discourage or prevent inappropriate infill development or redevelopment. A significant portion of the area is zoned for development in the SR-1 district, which is generally compatible with the objectives of the district, although this district allows higher density development than future development should be allowed within the overlay area. Almost all of the rural and semi-rural areas in the proposed overlay district boundaries rely on groundwater for water supply. Restricting densities in this area will serve to protect this water supply and avoid expensive and disruptive construction of new water lines within the overlay area.
2. The minimum setback from the Reservoir for any clearing, grading or construction activity should be 150 feet from the mean waterline of the Reservoir (120-foot elevation contour). The currently established Resource Protection Area (RPA) extends 100 feet from the reservoir – the added 50 feet provides a reasonable additional natural buffer and recognizes that, in many locations, slopes along the shoreline are quite steep. There is no room for dealing with failures in these areas, should problems arise.
3. The minimum setback from the Reservoir for installation of septic fields, tanks or other on-site subsurface sewage disposal system should be determined by the Health Department based upon site conditions, but should not be less than 150 feet, for the same reasons set forth above in item 2. The setback is all that appears necessary to complement Health Department requirements for these facilities.
4. The uses in the overlay district should be those currently permitted by existing zoning or as shown on the comprehensive plan. While no plan is “set in concrete,” the presence of the overlay district and its regulations will serve to deter the introduction of incompatible uses – mainly uses that require extensive clearing, grading and paving. Higher density residential uses may be proposed in the future. But comprehensive plan and zoning amendments for such uses will be subject to rigorous public review and are not likely to be approved unless they meet or exceed the levels of protection provided by low density development.
5. Except where already zoned for denser development, the density of new residential development within the overlay district should not exceed one dwelling unit per 5 acres on a gross acreage basis. Cluster-type development should be encouraged. A study of the effectiveness of Fairfax’s down-zoning in the Occoquan watershed indicates that the simple reduction in density achieved a significant reduction in pollutants flowing into the Occoquan Reservoir.
6. If large parking lots are built in the overlay district, then a higher standard of pollutant removal from storm water should be required. Since these facilities are expensive to install and maintain, uses requiring large parking lots will most likely not be proposed in the overlay district.
7. Uses that involve significant amounts of hazardous substances, such as gasoline stations, should be required to meet higher standards for containment of the substances than normally applied. Again, these uses will be less expensive to build in a location outside of the reservoir protection overlay district.
8. Wetlands in the overlay district should remain undisturbed, with minimum 50 to 100-foot undisturbed buffers around them (depending on slope). Wetlands in the overlay district should remain in place – they should not be removed and rebuilt in Haymarket. These wetlands perform important pollution-reducing functions for the reservoir where they are, at no cost to the public.
9. Intermittent and perennial streams should be protected with minimum 100-foot undisturbed buffers around them. The committee’s research indicated that significant amounts of silt and other pollutants can flow downstream from unprotected intermittent streams.
10. Slopes of 25% or greater should be left in their natural state. Clearing and grading of steep slopes causes soil erosion that is virtually impossible to control adequately, even using the required BMP’s, the construction of which also causes soil erosion and siltation. A basic concept of the overlay district is to minimize clearing and grading and to emphasize the use of existing natural processes to control soil erosion, rather than less effective and more expensive structural measures.
11. New on-site sewage treatment facilities should utilize recently adopted technology in order to remove more nitrogen than conventional systems are capable of doing. The overlay district should serve as a focus area for inspecting the performance of existing older individual systems and developing appropriate measures to assure proper maintenance of systems and retrofitting those that need to be upgraded or replaced.
12. Areas developed at urban densities or nearly urban densities within the overlay district could become areas where the County’s fledgling efforts at stream improvement could be focused. The existing storm water management systems in these areas should be reviewed in order to determine their adequacy and to develop appropriate maintenance and improvement measures where needed. Fortunately, many of these communities contain open space areas where pollutant removal systems could be built and maintained.
Voluntary Activities that Residents of the Overlay District should be encouraged to Adopt
Most of the residents in the proposed reservoir protection overlay district are living in this area because they were attracted by its characteristics. Notable among these characteristics are the native forests, slopes and streams where nature still can be seen and enjoyed. Even the more densely developed areas of Lake Ridge and its nearby communities contain areas of open space that are enjoyed by urban residents. The relatively low density of development in other parts of the overlay district area has allowed more extensive natural areas to remain or to be restored over time in residents’ yards and common areas. Many residents of the area have adopted ways of caring for their properties that reflect their interest in nature and the environment.
The committee suggests that all of the residents of the overlay area be informed and encouraged to adopt ways of caring for their properties that will help reduce harmful pollutants from entering the Occoquan Reservoir. The committee recommends that the County and related organizations focus on the residents of the overlay district to promote participation in activities such as the Audubon Society of Northern Virginia Habitat at Home Program, the National Wildlife Federation’s Backyard Habitat Program, the Virginia Department of Game and Inland Fisheries’ Habitat at home Program, the Virginia Department of Forestry’s Woods in Your Backyard Program, and the Monarch Butterfly Waystation Program.
All of these programs promote natural solutions to property management. While the principal purpose of these programs may be improving wildlife habitat, eliminating invasive species, or establishing forests, an accompanying benefit would accrue to water quality. A strong principle in these programs is to “do nothing,” that is, encourage Mother Nature to do her part in healing herself. This approach is often the best way to protect water quality. Taking this approach, residents would have less lawn and more trees, and storm water could be channeled to rain gardens, thereby reducing the amount of pollutants and storm water running off of their properties. Where lawns are present, property owners could be encouraged to minimize applications of fertilizer through new knowledge of optimal timing of fertilizer application and other factors. Home owner associations in the area could also utilize these programs for maintenance and improvement of association properties.
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