An engineering report being released today found several issues with Maryland Department of the Environment’s (MDE) issuance of a draft wastewater permit that would enable the proposed Lakeside at Trappe development to spray wastewater onto fields near Miles Creek and the Choptank River.
The report was written by the engineering and environmental consulting firm Antea Group. It was commissioned by the Chesapeake Bay Foundation (CBF) and ShoreRivers to review MDE’s preliminary approval of a wastewater permit for the development, which would add about 2,500 houses and apartments as well as a shopping center to the small Eastern Shore town of Trappe. The spray irrigation plan would allow the developer to spray an average of about 540,000 gallons per day of treated wastewater onto nearly 90 acres of fields near the project.
Antea determined that disposing of the new development’s treated wastewater by spraying it onto fields could create flooding and pollution problems that MDE overlooked by using outdated formulas and faulty assumptions. The firm’s experts did not agree with MDE’s finding that no pollution would leave the spray field.
In Maryland, spray irrigation of treated wastewater can only be permitted if MDE finds no nutrient pollution—such as nitrogen and phosphorus—can wash off the field or percolate into groundwater. To contain these harmful nutrients, which remain in treated wastewater at known levels, state law requires that they must be fully used by the vegetation with no losses to groundwater. Once in waterways, phosphorus and nitrogen fuel algal blooms that cause dead zones devoid of aquatic life. In this case, the pollutants could further exacerbate water quality problems in Miles Creek and the Choptank River. The Choptank is already impaired by too much pollution.
“Based on this report, it appears that Maryland Department of the Environment examined this permit with the goal of approving it, rather than evaluating it on its merits,” said Doug Myers, CBF’s Maryland Senior Scientist. “We do not agree with MDE’s finding that spraying hundreds of thousands of gallons of wastewater onto fields each day won’t cause more water pollution in the area. If anything, we urge MDE to evaluate this permit again with better information and more appropriate methodologies to determine how disposing wastewater in this way will affect water quality.”
Among the findings in the report:
- MDE evaluated how the wastewater will move through “clean sand, and sand and gravel” soil, however the soil type on the spray fields is “silty sand” which has different groundwater conductivity rates. Had MDE used the hydraulic conductivity rate for silty sand, the flooding potential estimated at the site would be much greater.
- Inaccurate groundwater conductivity analyses underestimate the potential for phosphorus and nitrogen pollution to pool on the surface and wash into nearby waterways.
- MDE did not provide a basis for requiring the development to store wastewater for 75 days. The requirement was put in place so the development would have somewhere to store wastewater when applications onto fields are prohibited, such as on rainy, windy, or freezing days when plants and soil wouldn’t be able to absorb water and pollutants as well. However, MDE did not use a climatological analysis to estimate how many days per year these conditions would require storage.
- MDE used a standard rate to determine vegetative uptake of pollutants by orchardgrass—the proposed vegetation expected to be used on the spray fields. This standard rate didn’t account for the fact that the plants are dormant during the winter. It also did not account for the substantial changes in uptake of nitrogen and phosphorus by orchardgrass and other vegetation during the growing season and other times of year.
- MDE used an outdated and rudimentary calculation method known as the Blaney-Criddle Method to determine how much water would evaporate from the spray fields. This method has been criticized by scientists for being especially inaccurate under “extreme” climatic conditions. The Antea consultants recommended instead that MDE use the Penman-Monteith method that incorporates standard climatic data into the formula to determine how much water will evaporate from the fields. If less water evaporates from the fields than expected it could result in flooding or pollutants reaching nearby waterways.
These findings and others in the report raise significant questions about whether MDE can accurately say, as they have previously, that using spray irrigation to dispose of treated wastewater at this proposed development will not add pollutants to local waterways.
"To say that no pollution will result from this proposed sewage treatment system is like saying that in Maryland water doesn't flow downhill and plants grow year-round. However, we're smarter than that,” explains Matt Pluta, Choptank Riverkeeper for ShoreRivers, “And we know that you can only apply so much treated sewage to a field before runoff or pollution of groundwater starts to occur. And we know that plants have a growing season where at certain times of the year they aren't using nutrients to grow. Thanks to the Antea Group we have a better sense of where this permit missed the mark on meeting the legal standards for protecting our rivers”
CBF and ShoreRivers remain concerned that MDE is using an agricultural method of wastewater disposal for a major suburban development project. In Maryland, most large developments connect to municipal wastewater plants that treat the wastewater and then release it directly back into a waterway only if the discharge does not exceed pollution limits. If an exceedance is anticipated, state agencies require that best practices such as tree plantings, stormwater controls, or enhanced farm management be used to offset any impacts to meet Chesapeake Bay restoration requirements.
Because MDE has found in reviewing this permit that no new pollutants will reach local waterways near the development due to the use of spray irrigation, best practices will not have to be put in place to reduce pollution that could be caused by these new homes and businesses.
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