The City of Danbury, CT has been issued a general permit for the discharge of stormwater into its stormwater system. This permit, General Permit for the Discharge of Stormwater from Small Municipal Separate Storm Sewer Systems, was re-issued January 9, 2013 under the authority of Section 22a-430b of the Connecticut General Statutes. The permit requires the City of Danbury to develop a stormwater management plan (SWMP), with minimum control standards such as: public education and outreach on stormwater impacts; Public Involvement/Participation; Illicit discharge detection and elimination; Construction site stormwater runoff control; Post-construction stormwater management in new development and redevelopment; and Pollution prevention/good housekeeping for municipal operations.
The City of Danbury primarily follows the stormwater regulations set forth by the Connecticut Department of Energy and Environment (DEEP) - and the aforementioned permit issued from the DEEP- however, Danbury has also adopted local zoning standards for stormwater drainage from residential, commercial, and industrial developments. Developments located in the City of Danbury's Aquifer Protection Area (APA) are subject to more intensive stormwater regulations, described in more detail below.
CT DEEP General Permit for the Discharge of Stormwater From Small Municipal Separate Storm Sewer Systems
5) Post-construction stormwater management in new development and redevelopment.
(A) Required throughout the municipality:
- develop, implement, and enforce a program to address stormwater runoff from new development and redevelopment projects that disturb greater than or equal to one acre, including projects less than one acre that are part of a larger common plan of development or sale, that discharge into the MS4 or directly to waters of the State. This program shall ensure that controls are implemented to require appropriate infiltration practices, reduction of impervious surface, creation of or conversion to sheet flow, measures and/or structures to reduce sediment discharge and any other innovative measures that will prevent or minimize water quality impacts;
- develop and implement strategies which include a combination of structural and/or non-structural best management practices (BMPs) appropriate for your municipality;
- use an ordinance or other regulatory mechanism to address the elements of subsection (i) above regarding post-construction runoff from new development and redevelopment projects to the extent allowable under State or local law; and
- ensure adequate long-term operation and maintenance of BMPs.
City of Danbury Zoning Regulations
10.B. ZONING PERMITS.
10.B.1. Zoning Permit.
a. An approved zoning permit shall be required from the Zoning Enforcement Officer or his/her designee before any of the following shall take place:
- a building or structure is erected, expanded, or reconstructed;
- a building or structure is relocated on the lot or moved to another lot;
- grading required to evaluate site conditions or for the preparation of the site for construction of an approved use, building or structure;
- the use of land, buildings, or structures is changed; or,
- new signs are erected.
b. Application for a zoning permit shall be made in writing to the Zoning Enforcement Officer from the owner of record of the lot or his/her authorized agent upon such forms as shall be prescribed by the Zoning Enforcement Officer. Such applications shall include the following.
- A description of the intended use(s) of the land, building(s) or structure(s).
- A plot plan drawn to scale by a land surveyor registered in the State of Connecticut showing:
- total tract boundaries and dimensions of the property drawn in accordance with an applicable Class A-2 survey, including scale, north point and easements;
- location of existing and proposed building(s), structure(s), sidewalks, wetlands, drainage structures, driveways and parking, and construction limit lines;
- existing and proposed setback distances;
- proposed grades, including top and bottom elevation of proposed retaining walls, to ensure final grades do not exceed a slope of one foot of vertical rise in two feet of horizontal distance; and,
- proposed or existing well and on-site sewage disposal systems as provided by the Health and Housing Department records. Where a record is not available, an inspection shall be made by the Health and Housing Department in order to ensure that the proposed use will comply with state and local health codes.
- All other information and graphic details necessary to determine compliance with these Regulations shall be provided.
Such plot plan shall be sufficient in scale for the Zoning Enforcement Officer to determine that all requirements of the Zoning Regulations have been met. The plot plan requirement is waived if a site plan is submitted in accordance with §10.D. of these Regulations.
- All other permits and required approvals from local and state agencies.
c. The zoning permit shall be issued upon a finding by the Zoning Enforcement Officer that the proposed activity is in compliance with the Zoning Regulations. Upon receipt of a zoning permit, the applicant may apply for a building permit from the Building Inspector.
d. Zoning permits issued as herein above set forth shall expire unless renewed by the Zoning Enforcement Officer, and become void if construction, use, work or other activity authorized by such permit is not:
- commenced within one (1) year of the date of permit issuance; or,
- completed within three (3) years of the date of permit issuance.
e. All valid building permits issued before adoption of these Regulations, but not yet expired, shall not be bound by these Regulations.
f. On-site Drainage.
On-site drainage improvements, whether connected or not connected to a City drainage system, shall be designed by and installed under the direction of a professional engineer licensed by the State of Connecticut. If rights to drain are required from property owners located downstream or down gradient of the site, such rights shall be obtained and evidence of such submitted to the Zoning Enforcement Officer prior to the issuance of a Zoning Permit. Prior to issuance of a certificate of compliance by the Zoning Enforcement Officer, the design engineer must provide a sealed written certification that the system, including the grading of the site, was installed in accordance with the design approved with the plan and is in good working condition. Certified record drawings of the installed drainage system must also be submitted by the design engineer for all drainage systems. Any connections to the existing City drainage system must be done under the supervision of and to the satisfaction of the Highway Department and the City Engineer or his/her designee.
10.D.4. Supplemental Documents.
One original and nine copies of each of the following supplemental documents, as applicable, shall be submitted along with the site plan. Failure to comply with these submission requirements shall render the application incomplete and may result in unnecessary delays or denial.
b. Utility Plans: The following utility plans and documents, including all construction details, notes and computations, shall be prepared, signed and sealed by a licensed professional engineer registered in the State of Connecticut, drawn in accordance with an A-2 Survey and in compliance with the design standards and criteria of the Engineering Department whenever the proposed development includes or is required to provide such improvements. Include the name and address of the individual or firm preparing the plan. Provide a copy of all calculations and related backup information that supports any assumptions or computations submitted for review.
(1) Sanitary Sewer: provisions for sanitary sewage disposal, including (1) location, size and type of existing and proposed on-site mains and laterals, pump stations and related sewage treatment facilities; (2) location, size and type of pipe of the nearest existing sanitary sewer to the proposed site and the existing or proposed connection to that sewer; and, (3) estimate of the volume of sewage expected to be generated by the proposal.
(2) Water Supply: (1) location and size of on-site public and private existing and proposed water mains and laterals, pump stations, storage tanks and related water supply facilities; (2) location, size and type of pipe of the nearest existing water supply to the proposed site and the existing or proposed connection to that supply; (3) needed fire flow analysis; (4) pressure in the existing City water system; and, (5) the licensed professional engineer’s verification of the adequacy of available water supply.
(3) Storm Drainage: provisions for storm drainage, including (1) catch basins, retention ponds, detention ponds, drywells, energy dissipaters, manholes, culverts, and similar facilities; (2) proposed drainage rights; (3) pre-development and post-development stormwater runoff computations for a 25-year 24-hour design storm; (4) computations for sizing and design of all components of the proposed drainage system; and, (5) analysis of adequacy of existing downstream drainage systems.
10.D.9. Stormwater Drainage.
All projects for which a site plan is required shall be designed so that there is no net increase in off-site stormwater runoff volume or peak flows from the twenty-five (25) year 24-hour design storm event. The applicant shall submit a stormwater management plan which adequately controls runoff to prevent flooding or pollution which may endanger public health or safety. The stormwater drainage system must be designed by and installed under the direction of a professional engineer licensed by the State of Connecticut. If rights to drain are required from property owners located downstream or down gradient of the site, such rights shall be obtained and evidence of such submitted to the Department prior to the issuance of a Zoning Permit. Prior to issuance of a certificate of compliance by the Zoning Enforcement Officer, the design engineer must provide a sealed written certification that the system, including the grading of the site, was installed in accordance with the design approved with the site plan and is in good working condition. Certified record drawings of the installed drainage system shall also be submitted by the design engineer for all drainage systems.
10.G. VIOLATIONS AND PENALTIES.
Penalties for violation of these Regulations shall be in accordance with Title 8, Chapter 124, Section 8-12. of the General Statutes of Connecticut, as amended.
8.A. EROSION AND SEDIMENTATION CONTROLS.
8.A.1. Purpose and Intent.
The City of Danbury hereby finds that significant quantities of soil are eroding from certain areas undergoing conversion to non-agricultural uses such as housing developments, industrial areas, recreational facilities, and roads. This erosion and resulting sedimentation makes necessary costly repairs which may wash out fills, roads, and embankments, clog storm sewers, muddy streams, and deposit silt in lakes and reservoirs. It is the purpose of this Section to control grading operations to prevent soil erosion and sedimentation from occurring as a result of non-agricultural development by requiring proper provisions for storm water disposal and the protection of soil surfaces during and after construction in order to promote the public safety, health, convenience and general welfare of the community.
City of Danbury, Engineering Division General Information & Guide
C. STORM DRAINAGE
- Pre-development and post-development runoff computations for the entire site based on a 25 year storm will be required. Where open channels, culve1ts and/or bridges are proposed or where open channels, culverts and bridges may be impacted by site improvements/development, the Engineering Division may require that these hydraulic facilities/stmctures be analyzed for 50, 100 and/or 500 year storm frequencies.
- Calculations for sizing the on and off site drainage systems (based on a 25 year storm) will be required.
- Either the Rational, TR-55 or TR-20 (where applicable) method is acceptable.
- Rights to drain from downstream property owner(s) will be required, if there is an increase in the rate of or volume of runoff discharged from the site, a change in the point of discharge of runoff from the site in question onto other property or if there is a decrease in runoff which has adverse effects downstream.
- The developer's engineer is to verify that surface runoff from any City road will not have a negative impact on the site. If runoff from a City road will impact the site, a drainage plan to handle this runoff is to be developed by the engineer for installation by the developer.
- Connections to existing systems:
- Calculations on the adequacy of the capacity of the existing downstream system will be required. If portions of the existing system are found to be inadequate, replacement of these portions of the existing system may be necessary.
- If connecting to a City system, the connection is to be made under the supervision of and to the satisfaction of the City's Highway Department.
- Retention Systems/Detention Systems/Drywells where proposed:
- Calculations (based on a 25 year storm) for the sizing of the storage required for the proposed development and of the outlet control are required.
- Percolation and deep hole tests are to be done and results submitted, if warranted.
- The installation of the system is to be done under the supervision of A State of Connecticut licensed engineer.
- After construction, the engineer who supervised the installation of the system is to submit to the City written certification that the system was installed as per the approved design.
- A reminder to the property owner that the system will remain a private one and that regular maintenance will be crucial to its continued functioning as intended is to be made.
- Adequate access to the system for maintenance purposes is to be provided.
- If the system is to be installed in a parking/driveway area, it is to be capable of handling minimum H-20 loads.
- A DEP dam permit may be warranted for a detention or retention pond.
- Anny Corps of Engineers approval is to be acquired, if warranted.
- Discharges are to be properly stabilized.
- Roof drains are to be shown on the plan.
- It is recommended that no portion (other than floor drains or underdrains) of a private on-site storm drainage system be located beneath a building or structure.
- If the development will discharge to a State of Connecticut storm drainage system, State Department of Transportation (DOT) approval will be required.
INSTRUCTIONS FOR DEVELOPING A STORMWATER MANAGEMENT PLAN FOR REGULATED ACTIVITIES IN THE CITY OF DANBURY AQUIFER PROTECTION AREA
(For developed sites in the AQUIFER PROTECTION AREA) [MAP]
This document contains information obtained from, and prepared by, the State of Connecticut Department of Energy and Environmental Protection (“DEEP”). It is intended to assist you with the stormwater management plan requirements of the City of Danbury Aquifer Protection Area Program. When the City of Danbury Aquifer Protection Agency or the City of Danbury Aquifer Protection Area Regulations requires a stormwater management plan, the plan shall ensure that stormwater run-off generated by the regulated activity is managed in a manner so as to prevent pollution of ground water.
Because many of the facilities in the Aquifer Protection Area have already registered for the DEEP General Permit Associated with Commercial Activity (GP-Commercial) or the General Permit for the Discharge of Stormwater Associated with Industrial Activity (GP-Industrial), those forms and the accompanying Stormwater Management Plan or Pollution Prevention Plan serve as the basis for the City of Danbury Aquifer Protection Agency Stormwater Management Plan (the “Plan”). Due to the sensitivity of aquifer protection area within the City, there are some special considerations beyond those in the general permits, so additional information is required in the form of a stormwater Supplement.
The information required in the Supplement should guide the revision of an existing registered Stormwater Management Plan or Pollution Prevention Plan. Facilities without an existing stormwater general permit should complete a registration form for GP-Commercial and develop the associated stormwater management plan. Such plan should include information below and required for the Supplement.
All stormwater management plans shall meet the requirements for the DEEP General Permit of the Discharge of Storm Water associated with a Commercial Activity (Commercial GP). Such requirements shall include:
1. A Registration Form that provides facility information, indicates the type of activity, and identifies stormwater discharge information including the number and type of conveyance.
2. A Stormwater Management Plan that includes measures for pollution prevention, pavement sweeping, outdoor storage and washing restriction, illicit discharge control, spill control/response, and maintenance and inspection of storm water structures. It shall also contain detailed information relative to the following:
- The Pollution Prevention Team or individual responsible for implementation of the plan;
- Identification of discharge points or potential pollution sources;
- Housekeeping measures;
- Spill control and response measures;
- Maintenance and inspection provisions and checklists;
- Employee training;
- Regular compliance evaluations;
- Future Considerations;
- Record keeping requirements;
- Monitoring requirements for industrial uses only;
- Plan Certification (see Attachment A); and
3. A Stormwater Supplement that addresses additional areas of concern to groundwater including the provision of measures necessary to prevent contaminated stormwater discharges/releases to the ground, application of stormwater discharge and treatment measures to protect groundwater quality, and encouragement of safe recharge of stormwater where it does not endanger groundwater quality. Additional management measures include: prevention of illicit discharges to stormwater discharged to the ground, provision of necessary impervious pavement in high potential pollutant release areas or “storm water hot spots” such as storage and loading areas, fueling areas, intensive parking areas and roadways, and discharge of paved surface runoff to aboveground type land treatment structures including surface drains, sheet flow surface swales, depressed grass islands, detention/retention and infiltration basins, and wet basins. These measures take advantage of natural treatment processes in soil and vegetation before discharge to the groundwater and promote natural aquifer recharge. The DEEP 2004 Connecticut Stormwater Quality Manual provides comprehensive stormwater guidance including potential groundwater concerns and is available on the DEEP’s website at www.ct.gov/deep/stormwater.
While the emphasis of the Plan and Supplement should be to minimize groundwater quality impacts of the runoff, a plan should be balanced and the extent possible include a combination of approaches to protect all water resources concerns including surface water quality and water quantity changes between pre-development and post-development runoff rates and volumes where possible. Most alternative site design designs, low impact development, and green infrastructure techniques will benefit groundwater except for certain direct infiltration techniques.
The Supplement shall provide the following information.
A. The identification of additional stormwater and site features of concern to groundwater (as applicable):
- Outline of buildings, sheds or other storage structures, pavement
- Stormwater structures and conveyances to the ground- drainage flow direction, infiltration areas and structures, and treatment or controls
- Location of fueling stations
- Location of loading/unloading areas
- Location of wastewater disposal systems- sewer line or septic system
- Location of waste storage and disposal areas including: dumpsters, used oil storage tanks, and other waste storage
- Location of liquid storage areas including: underground and above ground storage tanks, and their filling and discharging or distribution lines Location of any other outdoor structures or processing service areas that may impact groundwater or have materials exposed to precipitation.
B. A description of methods to prevent illicit discharges to the stormwater system.
Nothing but stormwater, uncontaminated groundwater seepage or permitted discharges are allowed into the stormwater system. Methods of discharge should be tested and analyzed to ensure that there are no unpermitted nonstormwater discharges at the facility. Testing methods should be documented and may include, but not be limited to, visual inspections of the facility and review of site plans, dry weather inspection of storm drains to ensure that there is no dry-weather flow, and dye or smoke testing if necessary. A testing schedule shall be identified. All plans should contain a statement that no washing of equipment or vehicles shall be permitted to take place outside where it can flow to the storm drain system. All washing must take place indoors, in an area where a permit has been obtained to discharge wastewater through an approved oil/water/grit separator to a municipal sewage treatment facility, or in an area where all wastewater discharges to a holding tank.
C. An approved site plan and statement contained within the Stormwater Management Plan that ensures no there is no outside storage of hazardous materials.
Outside storage of hazardous materials (including salt storage) is prohibited in the Aquifer Protection Area. All hazardous materials much be stored in a building or under a roof, on an impermeable surface that is protected from stormwater, inclement weather or hazards that can lead to a direct discharge into the ground. Regular inspection of all hazardous materials storage is required. Inspection schedules and reports shall be kept on site.
D. A list of all runoff management practices.
The Supplement shall list any runoff management practices used at the facility. Note appropriate descriptions or qualifications to the practices listed, such as the portion of the site affected. Runoff management practices may include catch basins, drainage swales, riprap channels or pools, detention/retention basins, infiltration basins or structures, impervious areas, sheet flow, biofilters or other measures used to manage/treat runoff. Management practices to be followed include directing runoff from paved surfaces to above-ground land treatment structures, surface drains, sheet flow, surface swales, depressed grass islands, detention/retention and infiltration basins, and wet basins. These practices provide an opportunity for volatilization of volatile organic compounds to the extent possible before the stormwater can infiltrate into the ground. Direct infiltration structures such as galleries, drywells, and leaching trenches do not allow for attenuation of salt or other soluble compounds that may be contained in parking lot runoff. New direct infiltration structures should not be installed and existing structures should be considered for replacement. If clean roof runoff can be segregated from stormwater, it is a good source of recharge to the aquifer. In this case, subsurface infiltration structures such as dry wells, galleries, or leaching trenches are appropriate and encouraged.
While the emphasis is to minimize groundwater quality impacts of the runoff, a plan should be balanced and the extent possible include a combination of approaches to protect all water resources concerns including surface water quality, water quantity changes between predevelopment and post-development runoff rates and volumes. Most alternative site designs, low impact development, and green infrastructure techniques will be beneficial to groundwater except for certain direct infiltration techniques. Non-structural measures to dissipate and treat runoff are encouraged, including sheet flow from uncurbed pavement and vegetated swales/basins.
If a stormwater collection system must be installed, it should discharge to an above-ground outlet point (swales, basins, channels, etc.) to prevent illicit discharges and fuel/chemical pollution releases to the ground.
E. Identification and mitigation of existing subsurface infiltration devices in stormwater hot spots.
Stormwater “hot spots” are areas or activities on the site with greater potential for high pollutant loads that may threaten groundwater quality. Examples of these include salvage areas, fueling facilities, dumpster or chemical storage areas, loading docks and large parking lots. In these areas, existing direct infiltration structures (galleries, dry wells, leaching trenches) are of particular concern as they can serve as a direct conduit for chemical pollutants to enter the groundwater and do not allow for attenuation of those chemical pollutants. Management of these stormwater hot spots should include measures to reduce potential impacts to groundwater such isolation of the “hot spot” by separating the activity or moving the activity to another location on the site. Examples include construction of a berm surrounding the activity to isolate it and redirect the stormwater runoff away from the infiltration device, construction of a swale to take the drainage from the hot spot away from the infiltration device, or relocation of an activity so that it does not drain to an infiltration structure. Stormwater discharge may also be pre-treated by modifying the infiltration device to include a grass or stone filter strip area around entrance, an oil-water separator, or media filters or inserts.
The Plan and Supplement shall also include regular monitoring and inspection of the area by employees, the keeping of temporary spill control devices on site such as speedy dry and absorbent pads, and regular maintenance and cleaning of the drainage area and infiltration structure.
City of Danbury Stormwater Documents
CITY OF DANBURY PLANNING & ZONING REGULATIONS
CITY OF DANBURY AQUIFER PROTECTION AREA (APA)
State of Connecticut Stormwater Documents