Tier 1
Status Quo. This assumes all jurisdictions maintain current level of effort in nutrient and sediment control programs. Programs and regulations that are already scheduled to go into effect before 2010 are included. It assumes that funding levels for programs remain unchanged. No new programs are introduced.

Tier 2
Once called the “maximum feasible” level of effort, it assumes the current mix of regulatory and voluntary programs are taken to maximum implementation levels (usually considered to be about 80 percent participation). Additional participation in voluntary programs would be motivated by increased incentives. It assumes nonpoint source control programs have unlimited funding to encourage participation, and that there is no limit on the cost-share amount given to individuals. Point source programs are also provided with incentives.

Tier 3
This is the “limit of technology” scenario. It assumes full implementation of the appropriate point and nonpoint source practices given unlimited funding and 100 percent participation. The only constraints considered are physical limitations, such as adequate space to implement nutrient control practices, or extreme cost increases.

Each tier was developed using implementation assumptions based on dozens of programs. Here are examples of the types of assumptions made in each tier about different programs:

  • Nutrient Management Plans. The plans, designed to optimize the use of fertilizer and to help prevent runoff, have been developed for about 2.3 million acres of cropland in the watershed. They would eventually cover 3 million acres in Tier 1, 3.85 million acres in Tier 2 and 4.24 million acres in Tier 3. In Tier 3, it is also assumed that one-third of those acres are enrolled in a “Yield Reserve Program” in which farmers are paid a premium to use less fertilizer than is called for in nutrient management plans.
  • Conservation Reserve Program and Conservation Reserve Enhancement Program. These programs, which provide farmers with incentives to take environmentally sensitive lands out production and plant buffers, now cover about 87,000 acres of cropland. In Tier 1, that would grow to 128,000 acres, in Tier 2 to 500,000 acres and in Tier 3 to 742,000 acres.
  • Cover Crops. These are planted in the fall to absorb excess nutrients left after harvest. They would increase from the current annual average of 153,000 acres to 1.5 million acres annually under Tier 2 and 2.2 million acres under Tier 3.
  • Yield Reserve. A potential new program that would provide farmers with an economic incentive to use less fertilizer than is prescribed in a nutrient management plan, thereby achieving further reductions in runoff. Tier 1 and Tier 2 do not include a yield reserve program, but Tier 3 assumes that 30 percent of cropland and hayland are in a yield reserve program.
  • Land Development. Tier 1 assumes land development continues at the current rate; Tier 2 assumes that the rate of development is reduced by 10 percent and Tier 3 assumes the rate of development is reduced by 20 percent.
  • Stormwater. Tier 1 assumes that 65 percent of new development has stormwater management; Tier 2 assumes that 75 percent of new development has traditional stormwater management, and that 25 percent of new development also uses low-impact techniques to further control runoff; Tier 3 assumes that half of new development has traditional stormwater management, and the other half uses low-impact development techniques.
  • Septic Systems. Tier 1 assumes no change from current programs; Tier 2 assumes that 10 percent of all new septic systems have nitrogen control technologies; Tier 3 assumes that all new septic systems have nitrogen control technologies and 1 percent of existing systems are replaced annually with systems that have nitrogen control technology.
  • Wastewater Treatment. Tier 1 assumes that all plants now planned for nutrient control upgrades are completed; Tier 2 assumes that all large plants in the watershed are upgraded with nutrient control technology that limits nitrogen concentrations to 8 milligrams per liter; Tier 3 assumes that all plants are upgraded to nitrogen control technology with nitrogen concentrations limited to 5 mg/l. (Traditional wastewater treatment, without nutrient controls, usually reduces nitrogen to a bit more than 20 mg/l.)