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CSO Long Term Control Plan (LTCP)

Long Term Control Plans (LTCPs) are required under the Environmental Protection Agency's combined sewer overflow (CSO) Control Policy and part of DEC's CSO control strategy to reduce the frequency, duration, and intensity of CSO events. Municipalities with CSOs are required to have a State Pollutant Discharge Elimination System (SPDES) permit.

The permit requires implementation of best management practices (BMPs) to reduce and control overflows. DEC developed fifteen best management practices that are technology-based controls designed to maximize pollutant capture and minimize impact to water quality.

If the best management practices are not enough to reduce CSO impacts to water quality, DEC requires CSO communities to develop and submit a Long Term Control Plan (LTCP).

Overview of the Long Term Control Plan approach

A Long Term Control Plan is a phased approach to control combined sewer overflows that will ultimately result in compliance with the NYS water quality standards and Clean Water Act requirements. The planning approach consists of three major steps: system characterization, development and evaluation of alternatives, and selection and implementation of the controls.

The plan has two phases for control of CSO events:

Phase 1: The municipality must develop a comprehensive study of the combined sewer system and research alternatives for reducing CSO impacts to water quality. This includes involving the public during the development of the plan, characterization of the sewer system, and evaluation of one or more CSO control alternatives. After finishing the LTCP, a schedule of construction and/or completion is developed. This schedule outlines how the approved CSO control alternatives will be implemented.

Phase 2: Upon DEC approval of the plan, DEC will either use a consent order or other enforceable action or modify the SPDES permit to include a schedule of compliance for the design and construction, implementation of the approved CSO control methods, and development of an operational plan and post-construction monitoring.

Phase I: Comprehensive study of combined sewer system and CSO impact to water quality

If it is determined that water quality standards in the receiving water are impacted by CSO discharges, the Combined Sewer Systems (CSS) community will:

  1. Research alternatives for mitigation of the impact of CSO discharges and choose one or more of those alternatives for implementation and submit documentation to DEC for approval.
  2. Suggest a schedule of construction or implementation of those alternatives, i.e., Phase II of the long-term control plan, to DEC.
  3. Implement the approved alternatives.
  4. Perform post-construction monitoring, once the control measures are in place, to ensure that the goals of the long-term control plan and the appropriate water quality standards are met.

A Long-Term Control Plan must be developed in accordance with the Guidance For Long-Term Control Plan, EPA, September, 1995, which will address the elements described below.

Elements of Phase I of the LTCP

Public participation plan

A public participation plan is an important part of developing the LTCP. An outline of how the permittee will involve the public throughout the LTCP development process must be included.

Characterization of the combined sewer system

A comprehensive characterization of the Combined Sewer Systems (CSS) is used to establish the existing baseline conditions, evaluate the effectiveness of the CSO technology based controls (best management practices) and determine the conditions upon which the LTCP will be based.

The CSS characterization plan includes:

  • interceptor sewer system,
  • thorough records review,
  • monitoring,
  • modeling, and other means as appropriate.

The characterization needs to adequately determine:

  • how the combined sewer system responds to various precipitation events;
  • identify the number, location, frequency, and characteristics of CSOs; and
  • identify water quality impacts that result from CSOs.

For a thorough characterization of the CSS, the following methods should be used:

  1. Review Rainfall Records - examination of the complete rainfall records for the CSS geographic area to evaluate the how the flow into the receiving water body changes and correlate between the CSOs and receiving water conditions.
  2. Review CSS Records - review and evaluate all available CSS records and perform field inspections and other necessary activities to identify the number, location, and frequency of CSOs and their location relative to sensitive areas and to pollution sources, such as significant industrial users, in the collection system.
  3. CSO and Water Quality Monitoring - develop a monitoring program that measures the frequency, duration, flow rate, volume, and pollutant concentration of CSOs and assesses the impact of the CSOs on receiving waters. Monitoring should be performed at a representative number of CSOs for a representative number of events. The monitoring program should include CSOs and ambient receiving waterbody monitoring and, where appropriate, other monitoring protocols, such as biological assessments, toxicity testing, and sediment sampling.
  4. Identification of Sensitive Areas - identify sensitive areas that CSOs may impact; including: waters with threatened or endangered species and their designated critical habitat, waters with primary contact recreation, public drinking water intakes or their designated protection areas and any other areas identified by the permittee or permitting authority, in coordination with appropriate State or Federal agencies.
  5. CSS and Receiving Water Modeling - use models that include appropriate calibration and verification with field measurements, to aid in the characterization. If models are used, a description and an explanation of why the model was selected and used should be documented in the characterization.

Combined sewer overflow control alternatives

The Long Term Control Plan outlines the alternative control strategies to reduce and/or eliminate CSOs. There are two approaches that a community can use to assess alternative controls to ensure compliance with Clean Water Act requirements: demonstrative and presumptive.

Demonstrative approach

The demonstrative approach must meet EPA's requirements by addressing the following:

  1. the planned control program is adequate to meet water quality standards and protect designated uses, and
  2. the CSO discharges remaining after implementation of planned control programs will not preclude the attainment of water quality standards or the receiving waters designated uses or contribute to impairment, and
  3. the planned control program will provide the maximum pollution reduction benefits reasonably attainable, and
  4. the planned control program is designed to allow cost effective expansion or retrofitting if additional controls are subsequently determined to be necessary to meet water quality standards or designated uses.

Presumptive approach

The presumptive approach must meet one of the EPA's criteria:

  1. no more than 4-6 overflow events per year that do not receive minimum treatment; or
  2. the elimination or capture for minimum treatment of no less than 85% by volume of the combined sewage collected during precipitation events on a system-wide annual average basis; or
  3. the elimination or removal of no less than the mass of the pollutants, identified as causing water quality impairment during the characterization, monitoring, and modeling effort.

Minimum treatment for (1) and (2) above is defined as: primary clarification to remove floatables and settleable solids, solids and floatables disposal, and disinfection of effluent, if necessary, to meet water quality standards according to regulations 6NYCRR Part 703.

In addition, the plan must include:

  • cost/performance curves that demonstrate that the EPA criteria are met by the control alternatives;
  • a description of the alternatives that were considered and why the selected alternatives were chosen and how they will be implemented; and
  • a schedule of implementation for the design and construction of the CSO alternatives. The schedule may be phased based on the relative importance of the adverse impacts on water quality standards and financial considerations.

The community should also consider expansion of the POTW treatment plant(s) secondary and primary capacity as one of the alternatives.

LTCP compliance dates

CSS communities are required to submit reports and plans associated with their progress or status of the LTCP on a regular schedule. EPA requires that the LTCP must be submitted to DEC within 2 years.

Description of Phase II of the LTCP

After DEC's approval of a combined sewer system community's LTCP, Phase II of the LTCP begins. In Phase II actions need to be taken by both DEC and the community to implement the LTCP. DEC will propose a modification to the SPDES permit in accordance with Uniform Procedures, 6 NYCRR - Part 621, to include changes or additions to the water quality requirements to meet water quality standards of the receiving waterbody. The CSS community must submit an implementation schedule that includes:

  • list of actions to be taken at each outfall and the expected due date for completion,
  • wet weather operating plan,
  • schedule of compliance for design and construction,
  • post-construction monitoring plan for the water quality parameters to ensure effectiveness of CSO controls and confirm that water quality standards are met,
  • any special conditions (for example, sensitive areas), and
  • frequency of reports to be submitted to DEC to document that the CSO controls are meeting the goals of the LTCP.

DEC monitors compliance with the CSO policy

The following are some of the DEC's monitoring strategies to ensure compliance with the policy:

  • Each CSO outfall in NY is required to have a SPDES permit and is required to report on the progress of implementing CSO controls included in the LTCP. Permittees are also required to continue implementing the applicable best management practices listed in their SPDES permit.
  • Permittees must complete and submit a CSO Annual Report Form (PDF, 1.2 MB) to report on the progress of their CSO control program.
  • DEC performs annual inspections and documents permittees progress on each of EPA's nine minimum controls and the CSO LTCP.
  • Implementation of the Sewage Pollution Right to Know law.