There are several regulatory requirements, documents and mandates which prescribed methods and procedures for communities to develop CSO LTCP documents. The major items which influenced the City’s planning are summarized in the following sections with a brief summary of their contents and their affect on the LTCP. Several of these documents can be viewed in their entirety in the Resources section.

The Indiana Water Pollution Control Board has established water quality standards for Indiana waterways. These standards, which have been approved by the federal government, serve as the legal basis for permit requirements under the 1972 Federal Clean Water Act (CWA). Water quality standards include “uses” designated by the state for each water body. Uses for a water body might include recreation, public water supply, industrial use, and irrigation. Water quality standards include pollution criteria to protect those uses and other policies designed to protect water quality. All Indiana waters are designated for aquatic life and full body contact recreation (often referred to as “fishable and swimmable”).

To meet the full body recreation standard, the maximum concentration of bacteria allowed in Indiana waters is 235 colonies E coli/100 ml. of water. There is an allowance for up to 10% of samples to exceed this standard as described in 327 IAC 2-1-6(d). This standard will likely be exceeded with any CSO discharge or with storm water runoff in urban and suburban areas. The State also has a 30-day geometric mean criterion of 125 cfu/100 ml but because CSO discharges are intermittent, this standard is not as restrictive as the “single sample maximum” criterion of 235 cfu/100 ml. The State has numeric criteria for other parameters and these were used with existing data to determine the pollutants of concern in the City’s CSOs.

The U.S. Environmental Protection Agency (EPA) issued a National Combined Sewer Overflow Control Strategy in 1989 (EPA, 1989). This Strategy reaffirmed that CSOs are point source discharges subject to National Pollutant Discharge Elimination System (NPDES) permit requirements. This Strategy was expanded and updated, resulting in the National CSO Control Policy published in 1994 (EPA, 1994). The Indiana Department of Environmental Management (IDEM) adopted the State’s Combined Sewer Overflow Strategy in 1996, based on the National CSO Strategy and Policy (IDEM, 1996). These three documents comprise the backbone for the site-specific NPDES permit requirements for Combined Sewer Systems (CSS) in the State of Indiana.

The Federal and State CSO policies are divided into two phases. Phase I focuses on implementation of technology-based requirements referred to as the Nine Minimum Controls (NMCs). The NMCs were developed to provide low-cost measures that could be implemented to reduce the magnitude, frequency and duration of CSOs. The City of Terre Haute satisfied this requirement with the development and submission of the CSO Operational Plan to IDEM. This document was last updated in 2006. Section 11 of the LTCP explains the necessary changes to the CSO Operational Plan as a result of the acceptance and implementation of the CSO LTCP.

Phase II of the federal and state CSO policies focus on meeting water quality based standards if the Phase I actions were found to be inadequate. The CSO control policies emphasize four key principles to ensure that CSO controls are cost-effective and meet the requirements of the CWA described as follows:

• Provide clear levels of control that would meet appropriate health and environmental objectives.
• Provide sufficient flexibility to municipalities, especially those that are financially disadvantaged, to consider the site-specific nature of CSOs and to determine the most cost-effective means of reducing pollutants and meeting CWA objectives and requirements.
• Allow a phased approach for implementation of CSO controls considering a community’s financial capability.
• Review and revise, as appropriate, water quality standards and their implementation procedures when developing long-term CSO control plans to reflect the site-specific wet weather impacts of CSOs.

CSOs are point source discharges and are subject to NPDES permit requirements. They are not subject to “limits based” parameters or secondary treatment requirements that are applicable to POTWs (EPA). The City of Terre Haute was issued its Phase II requirements in its NPDES permit in March of 1999. “Attachment A” of this permit outlines the Phase II requirements. The current NPDES permit is provided in the Resources Section. By permit requirements, Terre Haute was required to prepare a Stream Reach Characterization and Evaluation Report (SRCER) and a Long-Term Control Plan (LTCP).

The SRCER is intended to establish a “baseline” condition of the water quality of the receiving streams after implementation of the NMCs, prior to the implementation of any long-term control measures. Within the SRCER, it is to be determined if the currently permitted CSOs impact the receiving stream segments in Terre Haute. The City submitted its SRCER to IDEM in October of 2000.

The LTCP was to include the following minimum elements as defined by EPA’s CSO Control Policy:

1. Characterization, Monitoring, and Modeling of the Combined Sewer System;
2. Consideration of Sensitive Areas;
3. Evaluation of Alternatives;
4. Cost/Performance Considerations;
5. Revising the CSO Operational Plan;
6. Maximizing Treatment at the WWTP;
7. Use Attainability Analysis (if applicable)
8. Development of an Implementation Schedule;
9. Development of a Post Construction Compliance Monitoring Program; and
10. Public Participation.

These elements could be modified to meet Terre Haute’s unique conditions. The permit required that the City meet with IDEM early and frequently through the study to coordinate the development of the LTCP. At these meetings, IDEM and the City agreed on the data, information, and analysis needed to support the development of the LTCP. The City met with IDEM early in the LTCP development to discuss the project approach and then later in the project at milestone stages to discuss project status and findings. The permit also required the LTCP to assess the City’s financial capability to implement CSO controls to meet water quality standards.

Lastly, the permit required the LTCP to include monitoring and modeling activities to characterize the impact of CSOs on each stream, and targets environmentally sensitive areas. The plan incorporated community input in identifying priority areas and selecting the long-term CSO controls.

Terre Haute’s original and revised LTCP incorporates all of the above requirements.

Senate Enrolled Act 431 (SEA 431), signed by Governor Frank O’Bannon in March of 2000, established the circumstances under which a long-term control plan meets the state’s water quality goals for wet weather overflows. As codified in IC 13-18-3-2.3, the law requires that a long-term control plan fulfills the water quality goals of the state if:

• The plan provides for the implementation of cost-effective control alternatives that will attain water quality standards or maximize the extent to which water quality standards will be attained if they are not otherwise attainable;
• The plan provides, at a minimum, for the capture for treatment of the sewer system’s “first flush,” which carries solids that have settled in pipes between wet weather events or that have washed off of streets and parking lots at the beginning of a storm;
• The plan is reviewed periodically; and
• Additional, cost-effective controls are implemented as necessary, pursuant to the reviewed and updated plan.

SEA 431 required IDEM to provide guidance to explain the requirements of the use attainability analysis and the LTCP. IDEM released this guidance in September of 2001. SEA 431, EPA and IDEM policies and guidance require an evaluation of a reasonable range of control alternatives for various levels of controls (design storms). Cost-effectiveness is to be used as a guide for consideration of CSO controls. Sensitive areas and financial capability are also to be included in the evaluation of alternatives.

The appropriate level of CSO control must be defined based on water quality data, system performance modeling, and economic factors. These factors may support the revision of existing water quality standards.

SEA 431 requires municipalities to maximize treatment of wet weather flows at the treatment plant as part of the LTCP. Maximizing the use of existing wastewater treatment facilities to treat wet weather flow is a cost-effective way to reduce the magnitude, frequency, and duration of CSOs, which flow untreated into receiving waters. The municipality must submit documentation in the LTCP demonstrating a diligent effort to evaluate alternatives for increasing flow to the POTW.

Current IDEM and EPA policy requirements include some previous regulatory requirements along with newer directives as summarized below. A range of alternatives should be developed in each LTCP including “No Action”, complete elimination of all CSO impacts and a range of alternatives at varying numbers of overflow events per year. The alternatives were developed for a “typical year” of rainfall for the City of Terre Haute.

IDEM has approved the “typical year” of rainfall. They have also approved the design storm of 1.56 inches of rain in 17 hours. This is the equivalent of an event which would result in on average, 4 overflows per year per outfall.

Alternatives eliminating all overflows are deemed unaffordable considering other wastewater utility needs. However, several options and alternatives were evaluated and will be explained further in this document.

If total elimination of CSO impacts is considered to cause widespread economic and social hardship, the community must determine the point at which implementation of CSO controls would no longer cause widespread impacts. If water quality standards are not able to be met, the community can apply for relief of standards through the Use Attainability Analysis as described in the following section.

A Use Attainability Analysis (UAA) is a structured scientific assessment of the factors affecting the attainment of uses that are specified in Section 101(a)(2) of the Clean Water Act. IDEM recognizes that in many instances, a community will not be able to afford the total elimination of all impacts from CSOs. They recommend that if a community cannot afford to eliminate all of its CSOs, or demonstrate CSO control at regulatory accepted level, then that community should conduct a UAA. This UAA should demonstrate that attaining the use is not feasible due to one or more of the following six factors listed in 40 C.F.R. § 131.10 (g):

1. Naturally occurring pollutant concentrations prevent the attainment of the use
2. Natural, ephemeral, intermittent or low flow conditions or water levels prevent the attainment of the use, unless these conditions may be compensated for by the discharge of sufficient volume of effluent discharges without violating State water conservation requirements to enable uses to be met
3. Human caused conditions or sources of pollution prevention cannot be remedied or would cause more environmental damage to correct than to leave in place
4. Dams, diversions, or other types of hydrologic modifications preclude the attainment of the use, and it is not feasible to restore the water body to its original condition or to operate such modification in a way that would result in attainment of the use
5. Physical conditions related to the natural features of the water body, such as the lack of proper substrate, cover, flow, depth, pools, riffles, and the like, unrelated to water quality, preclude attainment of aquatic life protection uses
6. Controls more stringent than those required by sections 301 (b) and 306 of the Act would result in substantial and widespread economic and social impact.