Part 1: Guidelines | V. Wastewater Assessment Background
The WRE must address the availability of suitable receiving waters and land areas to meet wastewater treatment and disposal needs. Suitable means that surface waters can assimilate pollutants from wastewater sources, including wastewater treatment plants, community and individual septic tanks and industrial sources, without violating water quality standards. Suitable also refers to land areas that have the appropriate characteristics for ground water discharge of wastewater, which means that water quality standards will not be violated once ground water flows reach surface water bodies. Most surface waters are already considered impaired, or in violation of water quality standards, by the state as listed on the 303(d) list, which identifies each impaired water body and the standard or standards which it is violating. The state's 303(d) NPDES permit limits list is available at www.mde.state.md.us/Programs/WaterPrograms/TMDL/Maryland%20303%20dlist/ index.asp.
1. Nutrient Caps
Treated wastewater is discharged either to surface water or ground water via land application. When evaluating wastewater discharge permits, the state considers the nutrient caps of a water body or land area. The state has established two types of nutrient caps for wastewater discharge in Maryland:
* Point Source Caps: To help restore the Chesapeake Bay, the state has established the Chesapeake Bay Tributary Strategy point source caps for significant WWTPs (> 0.5 MGD) and point source projections for nonsignificant WWTPs (< 0.5MGD) that discharge to Chesapeake Bay tributaries.
* Total Maximum Daily Loads: To restore water quality in particular streams and other water bodies, the state has established TMDLs, which include a point source cap, also known as a point source waste load allocation. The TMDL also includes a nonpoint TMDL allocation that covers residential, agricultural and industrial pollutant sources via stormwater runoff, ground water pollution including septic system discharges and air pollution.
It is important to note that achieving wastewater discharge caps alone will not necessarily ensure that water body assimilative capacity is not exceeded. However, the caps are very important in helping the state and local jurisdictions make progress towards Chesapeake Bay and local tributary restoration.
For the state to authorize a wastewater discharge, the water body or land area proposed to receive the discharge must have the assimilative capacity to absorb the pollutant load in the discharge without violating water quality standards.
2. Impact of Water Quality Regulations on Land Use
Limited sewage treatment plant capacity and limited assimilative capacity of streams can inhibit or stop planned development. Therefore, the impact of regulations or other treatment capacity constraints on comprehensive plans and land use planning can be as constraining as the limits imposed by a lack of drinking water. The WRE must help to direct local comprehensive plans in ways that help to achieve wastewater disposal within water body assimilative capacities.
Options for addressing these limits include nutrient offsets, land application, growth limitation or redirection or, in the extreme, capping growth. As the regulations to govern the use of these or other techniques are completed, the basis for future updates of the WRE will be established.