Phosphorus Doesn't Migrate in Ground Water? Better Think Again!
USGS scientists have been studying the long-term migration of phosphorus
in a subsurface plume of treated sewage at the Toxic Substances Hydrology
Program's research site located in Cape Cod, Massachusetts. The ground-water
contamination resulted from 60 years of disposal of treated sewage to
infiltration ponds at the Massachusetts Military Reservation. Phosphorus
is a common constituent of agricultural fertilizers, manure, and organic
wastes in sewage and industrial effluent. Excess phosphorus in lakes is
a common cause of eutrophication.
The observed extent of the phosphorus plume and the interaction of the
plume with Ashumet Pond, a glacial kettle pond, has challenged scientists
to re-evaluate their understanding of the mobility of phosphorus in ground
water and of interactions between ground water and surface water.
- Phosphorus Mobility - In the past, ground-water scientists thought that phosphorus in
ground water migrated little and hence was of minimal ecological
concern. Years of monitoring data on phosphorus concentrations in the
plume of treated sewage on Cape Cod has shown that phosphorus does
migrate in ground water, raising concerns that phosphorus-containing
ground water discharging into Ashumet Pond may accelerate the
eutrophication of the pond. USGS scientists
are using their new understanding of the migration of phosphorus in
ground water to predict the phosphorus load to Ashumet Pond from the
sewage plume. The Massachusetts Department of Environmental Protection
(DEP) is using these results to develop technical guidance concerning
wastewater disposal to ground water. The DEP is concerned that land
disposal of wastewater through infiltration basins and septic leaching
fields can lead to discharge of phosphate-enriched ground water to sensitive
lakes and streams. USGS scientists have assisted State resource managers
in preparing guidelines for locating onsite wastewater disposal so that
discharge of phosphorus into streams, ponds, and coastal waters will
- Ground Water and Lakes - On the basis of past knowledge, scientists
expected the phosphorus plume to discharge into the pond over a broad
area in a cove on the western side of the pond. Monitoring data have
shown that the phosphorus plume rises steeply upward and discharges
to the pond in a narrow area within 100 feet of shore. This pattern
of discharge, in which the greatest inflow is at the shoreline, has
been reported in other lake studies by USGS scientists. Toxics Program
scientists are working closely with the Air Force Center for Environmental
Excellence and its contractors to design a remediation strategy that
is based on a sound scientific understanding of phosphorus fate and
transport. Actions to limit phosphorus discharge to the pond are now
being focused on the small discharge area rather than on the much larger
plume upgradient of the pond. Treating the discharge area is expected to be a more cost-effective
approach that will provide the maximum benefit to the pond's
Selected References on Phosphorus in the Sewage Plume
- Bussey, K.W., and Walter, D.A., 1996, Spatial and temporal distribution
of specific conductance, boron, and phosphorus in a sewage-contaminated
aquifer near Ashumet Pond, Cape Cod, Massachusetts: U.S. Geological
Survey Open-File Report 96-472, 44 p.
- LeBlanc, D.R., 1984, Sewage plume in a sand and gravel aquifer, Cape
Cod, Massachusetts: U.S. Geological Survey Water-Supply Paper 2218,
- McCobb, T.D., LeBlanc, D.R., Walter, D.A., Hess, K.M., Kent, D.B., and Smith, R.L., 2003, Phosphorus in a Ground-Water Contaminant Plume Discharging to Ashumet Pond, Cape Cod, Massachusetts, 1999: U.S. Geological Survey Water-Resources Investigations Report 02-4306, 70 p.
- Parkhurst, D. L., Stollenwerk, K. G. and Colman, J. A., 2003, Reactive-Transport Simulation of Phosphorus in the Sewage Plume at the Massachusetts Military Reservation, Cape Cod, Massachusetts: U.S. Geological Survey Water-Resources Investigations Report 03-4017, 40 p.
- Stollenwerk, K.G., 1996, Simulation
of phosphate transport in sewage-contaminated groundwater, Cape Cod,
Massachusetts: Applied Geochemistry, v. 11, no. 1-2, p. 317-324.
- Stollenwerk, K.G., and Parkhurst, D.L., 1999, Modeling
the evolution and natural remediation of a ground-water sewage plume,
in Morganwalp, D.W., and Buxton, H.T., eds., U.S. Geological
Survey Toxic Substances Hydrology Program--Proceedings of the Technical
Meeting, Charleston, South Carolina, March 8-12, 1999--Volume 3 of 3--Subsurface
Contamination from Point Sources: U.S. Geological Survey Water-Resources
Investigations Report 99-4018C, p. 371-382.
- Walter, D.A., and LeBlanc, D.R., 1997, Geochemical and hydrologic
considerations in remediating phosphorus-contaminated ground water in
a sewage plume near Ashumet Pond, Cape Cod Massachusetts: U.S. Geological
Survey Open-File Report 97-202, 20 p.
- Walter, D.A., LeBlanc, D.R., Stollenwerk, K.G., and Campo, K.W., 1999,
transport in sewage-contaminated ground water, Massachusetts Military
Reservation, Cape Cod, Massachusetts, in Morganwalp, D.W., and Buxton,
H.T., eds., U.S. Geological Survey Toxic Substances Hydrology Program--Proceedings
of the Technical Meeting, Charleston, South Carolina, March 8-12, 1999--Volume
3 of 3--Subsurface Contamination from Point Sources: U.S. Geological
Survey Water-Resources Investigations Report 99-4018C, p. 305-315.
- Walter, D.A., Rea, B. A., Stollenwerk, K.G., and Savoie, Jennifer,
1996, Geochemical and hydrologic controls on phosphorus transport in
a sewage-contaminated sand and gravel aquifer near Ashumet Pond, Cape
Cod, Massachusetts: U.S. Geological Survey Water-Supply Paper 2463,
89 p. (supercedes USGS Open-File Report 95-381).
More Information on the Cape Cod Sewage Plume
USGS Information on Phosphorus and Other Nutrients
USGS Information on Ground-Water/Surface-Water Interactions
- Ground Water and
Surface Water A Single Resource, U.S. Geological Survey Circular
1139 (see figure 4).
- Winter, T.C., 1999, Relation
of streams, lakes, and wetlands to groundwater flow systems: Hydrogeology
Journal, v. 7, no. 1, p. 28-45.
Thomas C., 2001, Ground Water and Surface Water: The Linkage Tightens,
But Challenges Remain: Hydrological Processes, v. 15, no. 18. p.
- Pfannkuch, H. O. and Winter, T. C., 1984, Effect of anisotropy and
ground-water system geometry on seepage through lakebeds, 1. Analog
and dimensional analysis: Journal of Hydrology, v. 75, p. 213-237.