This page provides general information on the purpose of each chapter, the summary of revisions made from the 2004 Manual, and when this chapter is applicable for usage. Click on a chapter for a drop down of this information as well as a link to a page for each chapter containing more in-depth information and access to PDF of Manual sections.
Background:
Understanding stormwater runoff and pollution, its impacts, and how climate change plays a role:
Chapter 1: Introduction
Changes have been made but there is little impact on the general stormwater permits.
Purpose / Overview
- Describes the Manual’s adoption, purpose, current and future revisions, users and organization, and applicability and regulatory basis
Changes / Revisions
- Summary of major revisions to the Manual and where to find information on future updates
- Updates to the organization and use of the Manual
- Updates to the applicability and regulatory basis of the Manual
- Updated descriptions of federal, state, and local regulatory stormwater programs as they relate to the Manual (moved to the Manual appendices)
How to apply it
- Overview tool for what to expect within this newest version of the Manual
Chapter 2: Stormwater Impacts
Changes have been made but there is little impact on the stormwater permits.
Purpose / Overview
- Describes stormwater runoff and its impacts on watershed hydrology, water quality, and ecology
- Introduces the concept of impervious cover and the importance of disconnecting Directly Connected Impervious Area (DCIA)
- Understanding climate change impacts on stormwater quality
Changes / Revisions
- Advances in scientific understanding of the water quality impacts of stormwater runoff
- Concepts of Directly Connected Impervious Area (DCIA) and DCIA disconnection from the CT DEEP MS4 General Permits
- Discussion of climate change impacts and stormwater management
How to apply it
- Overview or refresher to the hydrological, stream channel, floodplain, water quality, and ecological impacts of stormwater runoff and why it must be addressed
- Understanding the various pollutants of stormwater runoff, their origins, and impacts
- Overview or refresher of impervious area, directly connected impervious area, and its relationship with stormwater
- Understanding the relationship between climate change and stormwater management
Chapter 3: Preventing and Mitigating Stormwater Impacts
Changes have been made but there is little impact on the stormwater permits.
Purpose / Overview
- Overview of approaches for preventing and mitigating stormwater impacts through LID site planning and design, source controls and pollution prevention, construction soil erosion and sedimentation controls, and post-construction stormwater management
Changes / Revisions
- Streamlined stormwater management framework and elements
- Recategorized structural stormwater BMPs based on function
How to apply it
- Overview or refresher of various approaches to dealing with stormwater
Design:
Pathway of utilizing Low Impact Development first and foremost, followed by guidance and criteria for structural stormwater BMPs
Overview of standards and performance criteria for land development projects and on site stormwater BMPs (structural and non-structural); applies to all new development, redevelopment, retrofits, and other land disturbance activities:
Chapter 4: Stormwater Management Standards and Performance Criteria
Purpose / Overview
- Describes updated stormwater management standards and performance criteria for all new development, redevelopment, and retrofit projects, as well as any land disturbance activities
- Stormwater Standards:
- 1: Runoff Volume and Pollutant Reduction
- 2: Stormwater Runoff Quantity Control
- 3: Construction Soil Erosion and Sediment Control
- 4: Post-Construction Operation and Maintenance
- 5: Stormwater Management Plan
- Stormwater Standards:
- Explanation and calculation for updates stormwater retention and treatment standards
Changes / Revisions
- Updated and streamlined stormwater management standards and performance criteria
- Consistency with post-construction stormwater management retention and treatment requirements in the CT DEEP stormwater general permits
- Updated design storm precipitation for stormwater quality and quantity control
- Water Quality Storm variable within Water Quality Volume equation updated from 1 inch to 1.3 inches
- Use of EPA stormwater BMP performance curves and pollutant-specific load reduction targets when retention of the applicable water quality volume is not achievable
How to apply it
- To review the stormwater management standards for new developments, redevelopment, retrofits, and all other land disturbance activities subject to post-construction requirements
- MS4 Permit:
- Under Minimum Control Measure 4 (Construction Site Stormwater Runoff Control), towns must require developers, construction site operators and contractors to be consistent with these practices and standards
- Under Minimum Control Measure 5 (Post-Construction Stormwater Management), towns must retain 50% or 100% of the Water Quality Volume based on the site for all re- and new development
- Construction Permit:
- All construction regulated by the CT Construction Stormwater General Permit must retain 50% or 100% of the Water Quality Volume
- Industrial Permit:
- Any construction and or structural/non-structural stormwater controls onsite must adhere to set standards by the manual with regards to retaining 50% or 100% of the Water Quality Volume
- MS4 Permit:
- Provides stormwater management standards in regards to runoff volume and pollutant reduction
Emphasis on low impact development design (non-structural) first to reduce stormwater impacts and prevent pollutant exposure to stormwater:
Chapter 5: Low Impact Development Site Planning and Design Strategies
Purpose / Overview
- Addresses non-structural Low Impact Development (LID) site planning and design strategies that can be used to reduce or disconnect impervious surfaces and retain and infiltrate stormwater on-site, thereby eliminating or reducing the need for structural stormwater BMPs
- Integrates information from the 2011 LID Appendix and provides additional guidance on the LID site planning and design process, hydrologic analysis, and criteria/credits for reducing DCIA through simple disconnection and other non-structural site planning and design techniques
Changes / Revisions
- Replaces and integrates the 2011 Low Impact Development Appendix into the revised Manual
- Streamlines content to focus on non-structural LID site planning and design strategies (Chapters 7 through 13 address structural LID measures)
- Provides additional guidance on the LID site planning and design process, LID hydrologic analysis, and criteria/credits for reducing DCIA through simple disconnection and other non-structural site planning and design techniques
- Incorporates LID credits to help quantify the benefits and incentivize the use of certain non-structural site planning and design techniques for meeting the runoff volume and pollutant reduction standard in Chapter 4
How to apply it
- Review of what Low Impact Development is and key elements of implementation, such as site planning, design technique, and proper usage for avoiding / reducing negative impacts of stormwater runoff
- Provides LID implementation information for various areas of source pollution
- Review of disconnection and conversion of impervious surfaces for credits
Chapter 6: Source Control Practices and Pollution Prevention
Purpose / Overview
- Addresses source control and pollution prevention practices, which are operational practices to limit the generation of stormwater pollutants at their source
- Typically non-structural
- Minimum or no land area
- Can be implemented with moderate cost and effort (compared to structural BMPs)
- Abbreviated to provide website links to current information on common source control and pollution prevention practices
Changes / Revisions
- Clarified project types and land use activities for which source control practices and pollution prevention should be implemented
- Minimum requirements for source control practices and pollution prevention
- Updated information on source control and pollution prevention practices with website links to sources of additional information
How to apply it
- Before implementation of structural BMPs; use when considering non-structural practices to control source pollution
- Breakdown of pollution prevention measures, which land use type they impact, minimum requirements of federal permits and what constitutes it as controlling or preventing source pollution, as well as sources for additional information
Consideration and selection of structural stormwater BMPs after low impact development has been considered / implemented where possible:
Chapter 7: Overview of Structural Practices and Pollution Prevention
Purpose / Overview
- Introduces functional categories of structural stormwater Best Management Practices (BMPs) that can be used after consideration and use of LID site planning and design techniques to meet the stormwater management standards and performance criteria described in Chapter 4
Changes / Revisions
- Recategorized structural stormwater BMPs based on function, replacing previous “Primary and Secondary Treatment Practices” terminology and framework
- Increased flexibility for selection and design of structural stormwater BMPs to meet stormwater management standards and performance criteria
- General guidance on BMP design considerations to reduce or facilitate maintenance
How to apply it
- Overview and breakdown of the main categories of BMPs:
- Pretreatment
- Infiltration
- Filtering
- Stormwater Pond
- Stormwater Wetland
- Water Quality Conveyance
- Stormwater Reuse
- Proprietary
- Other BMPs and BMP Accessories
Chapter 8: Selection Considerations for Stormwater BMPs
Purpose / Overview
- Provides guidance on selecting appropriate structural stormwater BMPs for a development site based on the requirements and needs of the site
- Includes an updated selection process and selection factors
Changes / Revisions
- Updated BMP selection criteria and matrices consistent with re-organized functional classifications
- New flowchart to aid in the BMP selection process for a given project and site
- To guide designers and reviewers
- Prioritization of retention BMPs in the selection process consistent with updated stormwater management standards and performance criteria
- New selection factors related to climate resilience
- Sea level rise and coastal considerations in the selection and design of stormwater BMPs in coastal areas, as well as design considerations for mitigating the potential negative impacts of climate change on stream temperatures and nutrient loads
How to apply it
- Breakdown and guidance when choosing stormwater BMPs
- Suitability:
- Retention
- Treatment
- Pretreatment
- Peak runoff attenuation
- Physical feasibility factors
- Contributing drainage factor
- Site slope
- Soil infiltration capacity
- Depth to seasonal high ground water table and bedrock
- High risk sites and drinking water supply area
- Receiving Water Selection Factors
- Coldwater streams
- Freshwater lakes and ponds
- Coastal waters and estuaries
- Suitability:
Guidance on stormwater BMPs for retrofitting sites which are already developed to improve stormwater quality and reduce overall stormwater quantity:
Chapter 9: Stormwater Retrofits
Purpose / Overview
- Describes techniques for retrofitting existing developed sites to improve or enhance the water quality mitigation functions of the sites
- Discusses the conditions for which stormwater retrofits are appropriate and the potential benefits of stormwater retrofits
- Discusses the role of stormwater retrofits in meeting DCIA disconnection goals for municipal stormwater management programs
Changes / Revisions
- Consistency with stormwater retrofit requirements in the CT DEEP stormwater general permits
- Reflecting the importance of retrofits to the success of municipal stormwater management programs in achieving the DCIA disconnection goals of the CT DEEP MS4 General Permit
- New guidance on retrofit planning approaches
- Updated information on stormwater retrofit types and applications
- Use of stormwater retrofits for DCIA disconnection and reduction
- Use of EPA stormwater BMP performance curves for retrofit sizing and crediting
- Updated information on other resources and tools for stormwater retrofit planning and design
- Incorporates and/or references information from a regional stormwater retrofit manual that has been developed for New England
How to apply it
- For more information when considering retrofits and various approaches to take
- Provides criteria for when credit is received for disconnection and reduction for impervious area conversion, disconnection, and both new and modified structural stormwater BMPs
Guidance on infiltration and pretreatment for stormwater BMPs to meet retention standards and further reduce pollutants in stormwater runoff:
Chapter 10: General Design Guidance for Stormwater Infiltration
Purpose / Overview
- Addresses the design of stormwater infiltration systems, including updated guidance on site suitability, soil evaluation methods, sizing methods, and other general design requirements for stormwater infiltration systems
Changes / Revisions
- New addition to the Connecticut Stormwater Quality Manual
- Provides general design guidance for stormwater infiltration systems, which are a key practice for meeting on-site stormwater retention requirements
- Includes updated guidance on site suitability, soil evaluation and infiltration system sizing methods
How to apply it
- Necessary design guidance for infiltration-based structural stormwater BMPs
- Design infiltration volume
- Sizing methods
- Static method
- Dynamic method
- Information on soil evaluation
- Information on land uses or activities with higher potential pollutant loads
Chapter 11: Proprietary Stormwater BMPs
Purpose / Overview
- Provides guidance on the appropriate use of proprietary stormwater BMPs, as well as new or emerging technologies, including criteria for evaluating the use of such systems and recommended third-party performance programs and testing criteria
Changes / Revisions
- Describes uses and limitations of proprietary stormwater BMPs
- Appropriate use of proprietary stormwater BMPs
- Identifies new or emerging technologies, including criteria for evaluating the use of such systems and recommended third-party BMP performance verification programs for use in Connecticut
- Provides general design criteria and maintenance requirements for proprietary BMPs
How to apply it
- Further information about proprietary stormwater BMPs
- Proprietary BMPs: manufactured systems that use proprietary settling, filtration, absorption/adsorption, vortex principles, vegetation, and other processes to remove pollutants from stormwater runoff
- Pre-treatment for other BMPs
- General design criteria and maintenance
- Proprietary BMPs: manufactured systems that use proprietary settling, filtration, absorption/adsorption, vortex principles, vegetation, and other processes to remove pollutants from stormwater runoff
Plan documents all proposed land disturbance projects (development, re-development, retrofit) along with chosen stormwater measures to mitigate stormwater pollution:
Chapter 12: Stormwater Management Plan
Purpose / Overview
- Describes how to prepare a stormwater management plan for review by local and state regulatory agencies
- Includes a recommended plan format and contents, and a completeness checklist for use by the plan preparer and reviewer
Changes / Revisions
- Updated Stormwater Management Plan content consistent with revised stormwater management standards and performance criteria
- Updated Stormwater Management Plan Checklist (Appendix E)
How to apply it
- Overview or refresher of the stormwater management plan and what it requires
- Plan content
- Stormwater management report
- Summary of compliance
- Design calculations
- Design drawings
- Soil erosion and sediment control plan
- Operation and maintenance plan
- Other supporting documents
- For MS4 municipalities who need to update their plan or for new MS4 municipalities
- For other stormwater permits which may require a SWMP
- Construction and industrial (stormwater pollution prevention plan; stormwater pollution control plan)
- For other stormwater permits which may require a SWMP
The ‘nuts and bolts’ of implementing a structural stormwater BMP – design, construction, maintenance, etc.:
Chapter 13: Structural Stormwater BMP Design Guidance
Purpose / Overview
- Provides detailed technical design guidance for each of the structural stormwater BMPs
- Includes guidance on the selection, design, construction, and maintenance of these practices, as well as summary information on selection and sizing criteria addressed in previous chapters
Changes / Revisions
- Updated design guidance for specific types of structural stormwater BMPs with a focus on practices that are most used to meet the retention and treatment standards in the revised Manual When to use it
How to apply it
- Detailed guidance on structural stormwater BMPs
- Consult when implementing BMPs for retrofits