A WATER QUALITY STUDY OF THE ELIZABETH RIVER: THE EFFECTS OF THE ARMY BASE AND LAMRERT POINT STP EFFLUENTS by Bruce J. Neilson Special Report No, 75 in Applied Marine Science and Ocean Engineering A Report to Hayes, Seay, Mattern and Yattern Virginia Institute of Marine Science Gloucester Point, Virginia 23062 William J. Hargis, Jr. Director May 1975 TABLE OF CONTENTS Page Chapter 1. Conclusions and Recommendations ........... 1 Chapt Chapter 3 . The Fate of Materials Discharged into the Elizabeth River System ................ 12 Chapter 4 . Water Quality in the Elizabeth River System .................................... 44 Chapter 5 . Summary ................................... 52 Chapter 6 . Acknowledgements .......................... 54 Chapter 7 . References ................................... 55 Appendix A . Hydrologic and Climatological Data ........ 56 Appendix B . Data on Sewage Treatment Plants Discharging to the Elizabeth River System ................................... 66 Appendix C . Biological Surveys ........................ 71 Appendix D . Data from Water Quality Surveys and Dye Studies ............................... 83 Appendix E . Elizabeth River Model ..................... 103 CHAPTER 1. CONCLUSIONS AND RECOMMENDATIONS 1) An analysis of the slack water data from 1974 indicates that when strong stratidication exists in Hampton Roads, there will be strong vertical stratification in the Elizabeth River system as well. For these conditions, a non-tidal circulation will be set up which will enhance the exchange of water between the Elizabeth River and Hampton Roads. Therefore, water quality conditions within the ~lizabethkill be improved by this additional flushing. 2) Although tidal currents in the Elizabeth River system are weak and the maximum speeds are on the order of 0.5 knots (0.25 m/sec), mixing due to tides and other factors is not weak. In fact, the mixing mechanisms are suffi- ciently strong to oqercome vertical and horizontal density differences, resulting in a well-mixed and nearly homo- geneous body of water which may reach from Craney Island to the Portsmouth Naval Shipyards, These conditions arise when the freshwater flows to the James and the Elizabeth Rivers are low and stratification in Hampton Roads is moderate to weak. This can occur anytime during the year. 3) When the Elizabeth River is well-mixed, the non-tidal circulation is very weak or non-existent. Con- sequently residence times are quite large. The time re- -- - - -- - - - - --- -- - - -- - - - -- -- quired for the system to reduce the amount of an injected substance to 10% of the initial amount for the September 1973 hydrographic conditions varies from 13 days for sub- stances introduced near Craney Island to 40 days for sub- stances released in the upper reaches of the Southern Branch. 4) Water temperatures, especially in the Southern Branch, are elevated due to thermal discharges from power generating stations. Values between 25O and 30° centigrade have been measured in September 1973. It is believed that these high temperatures, in combination with the long residence time, cause a significant portion of the oxygen demand of waste waters to be exerted within the Elizabeth River System. 5) Field surveys have found violations of the current dissolved oxygen standards during several months of the year, primarily the summer months, and over several miles of the river. 6) Since the assimilation capacity of the river is limited by physical factors beyond man's control, the only remaining method to maintain water quality standards is to reduce the loadings of oxygen demanding substances tothesystem and/or to move the p~int~njectioncloser to the river mouth. Unfortunately, some sources are difficult to control (e.g. non-point sources and urban runoff) and advanced treatment is expensive. The dis- persion and residence times are such that a change in the location of the Lambert Point outfall within the Elizabeth River system (e.g. discharge near the present Army Base outfall) is expected to produce only a very modest improvement in water quality. Therefore, it is believed that DO violations will continue to occur until the total input of oxygen demanding substances is greatly reduced. 7) At this time it is not possible to assess the effects of moving the Army Base and Lambert Point out- falls into Hampton Roads with any certainty, since the characteristics of the circulation there are not well-known, It is believed that the water which leaves the Elizabeth River during ebb tide tends to retain its identity and, to a great extent, returns on the subsequent flood tide, If this is true, then the discharge point would have to be located either well into the natural channel at a depth of 20 feet or more or at or beyond Sewell's Point before the water quality in the Elizabeth River was improved significantly. CHAPTER 2. INTRODUCTION In the past decades the Hampton Roads metropolitan region has experienced rapid population growth and industrial development. The Norfolk-Portsmouth portion of that region, which includes slightly over two-thirds of the population of the total area, is centered on the Elizabeth River system. This river receives the waste products which normally are generated by industrial and population centers: domestic waste waters, thermal discharges, and wastes generated by industry, shipbuilding and shipping. As a result, the Elizabeth is "an example of an excessively utilized waterway in regard to waste assimilation" (Pheiffer, et al., 1972). Two large municipal sewage treatment plants (STPss), the so-called Army Base and Lambert Point plants of the Hampton Roads Sanitation District, discharge 14 and 25 million gallons per day (MGD; 0.6 and 1.1 cubic meters per second) of treated waters respectively to the Elizabeth River system. The present study was undertaken to investigate the means by which and the rates at which materials discharged into the Elizabeth River are dispersed through and flushed out of the system. The primary focus of this exercise was to determine whether the existing outfall sites for the two STP's were so situated to minimize effects on water quality and if this were not the case, to note superior sites. The Elizabeth River System The Elizabeth River system is comprised of the main stem of the Elizabeth (from Sewell's Point to Town Point), the Lafayette River and the Western, Eastern and Sazkh-Bra~~&s-ass kewni;n4%gur c3 1. T-fleELiz-afxrth is part of the Intracoastal Waterway maintained by the Corps of Engineers. At the head of the Southern Branch the Waterway bifurcates, providing two inland routes between Chesapeake Bay and Albermarle Sound. One route passes through Great Bridge along the Chesapeake and Albemarle Canal, down the North Landing River and into Currituck Sound. The locks at Great Bridge control the flow of water and mark the point where the tidal waves from the two water bodies meet. Since both halves of the Waterway are tidal, it bas been stated that there is no net flow through the locks, and therefore that this waterway does not con- tribute any freshwater to the Elizabeth River system (Corps of Engineers, 1974). However, it is possible to have a net flow if certain relationships exist between the tidal phases and amplitudes on the two sides of the locks. It also must be noted that water level fluctuations in Currituck Sound are dominated by the wind rather than the astronomical tides. Therefore, there very well could be a net flow into or out of the Elizabeth River system, but to this date, no measurements have been made by the Corps or other agencies which would allow this flow to be estimated Western Branch Southern Branch Great Bridge STP Figure 1. The Elizabeth River Syskem. or calculated. For this study the flow from the Chesapeake and Albermarle Canal has been assumed to be zero. The second route follows the Dismal Swamp Canal and provides access to Albemarle Sound near Elizabeth City, North Carolina. From an hydraulic poin_ttoffviewW,- the Dismal Swamp represents the high point of this region and water flows away from Lake Drumrnond in nearly every direction. The flow to the Southern Branch of the Elizabeth River is controlled by the locks and spillway at Deep Creek. This flow of water is the only natural Source of water which has been measured over the years. The long-term average monthly flows and the monthly flows for recent years ake gkven in Figure A-1 and Table A-2 in Appendix A. The long- term yearly average flow through the locks and spillway is 3 2309 million gallons per month (8,740,000 m /month) or 77 3 MGD (3.4 m /sec). During most of the year, the major portion of the flow enters via the spillway. ~uringthe dry part of the year, late summer and early fall, the flow is con- trolled by the lockages which increase due to use of the Intracoastal Waterway by small craft. Since the entire drainage basin for the Elizabeth River lies very close to the Atlantic Ocean and entirely within the Coastal Plain provinces, the topographic relief is slight. The maximum natural elevation is on the order of 25 feet above mean sea level. The total area of the drainage basin is around 300 square miles. Urbanization normally increases the portion of rainfall that goes directly into overland runoff and reduces the portion which soaks into the ground and enters the groundwater supply, since large areas are paved or otherwise covered with impervious mater- ials. These three factors, low relief, small drainage a-r-Lu-,-z&lwaz~~~ groundwater flow into the Elizabeth and to increase the magnitude of the peak flows during rainy periods. Thus the freshwater input from the tributaries is low during dry periods and has high peaks during wet periods. Since there are no gaging stations on any of these tributaries, this description remains an estimate of how the system works and may not always hold true.