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The following text is drawn from the Danbury Plan of Conservation and Development Town Plan which became effective in 2002. all of the text that follows in this section is copied directly from the Danbury Plan:

The City of Danbury has extensive municipal sewer and water supply service areas covering the most densely populated areas of the City. At present, most scheduled capital improvements for the two systems are limited to rehabilitation and replacement projects rather than major service expansions.

However, adopted sewer and water plans propose substantial expansions in the future. Additionally, with more stringent federal regulations in place under the Safe Drinking Water Act, community water systems are seeking to be taken over by larger systems such as the Danbury Water Department.

The West Side is where the most utility demand is anticipated as substantial new growth is projected in housing, light industry and commercial development. While municipal sewer lines serve a portion of the area, some are inadequate for projected growth. Thus, one of the City's largest capital projects will at some future time be the construction of a sewer interceptor and its network transporting West Side sewage flows to the downtown sanitary sewer system and ultimately to the municipal treatment plant off Plumtrees Road.

The second major utility issue concerns the effect of sewer systems on the public water supply watershed's in Danbury. Sewers are not, by themselves, harmful to these watersheds, and in fact can be beneficial if they correct failing septic fields and mitigate the threat of contamination or industrial discharges. However, the extension of sewer service may also encourage growth into areas that heretofore were largely undeveloped. The additional development may result in increased runoff, pollution, and the diversion of groundwater away from the watershed.

Generally, the City's policy is to allow only on-site sewage disposal systems within the watershed areas, and to allow extension of sewer services to these areas only if the on-site systems are failing and repairs are infeasible. The exception to this policy is the Lake Kenosia area on the West Side, as sewer service was installed there prior to the Lake's designation as a public water supply source.

Lake Kenosia and its watershed are now elements in the City's potable water supply. Thus, the West Side will become an important test of the City's ability to promote economic development while protecting public water supply watersheds.

The City of Danbury provides sanitary sewer service to its most densely populated area and to several adjacent towns in the region. The sewage treatment plant has a permitted treatment capacity of 15.5 million gallons per day (mgd), and is operated under a permit granted by the Connecticut Department of Environmental Protection (DEP).

The City has entered into a twenty year contract with U.S. Filter Operating Services to operate the plant but retains ownership of the plant, pumping stations, and collection system. The 1990-93 expansion project added capacity, improved treatment, and greatly reduced the pollutants discharged into the Still River, especially ammonia. The plant's operations permit lapsed several years ago but DEP has allowed the plant to continue to operate while the new permit is pending.

The sewage treatment plant dechlorinates and nitrides the effluent prior to discharge. Depending on changing state standards, the updated permit may require additional effluent treatment. This may include a reduction in levels of metals (such as lead, copper, silver, and zinc) and in levels of nitrogen, changes that may require a substantial capital investment. Additionally, converting some of the chemicals used from gaseous to liquid form may be required to meet worker safety standards.

The Danbury plant's 15.5 million gallon per day (mgd) capacity is allocated primarily to the City (11.8 mgd), with varying amounts to Bethel, Brookfield, Newtown, and Ridgefield. The four towns have not yet reached their full allocation. In addition, one million gallons per day are dedicated to regional needs that can be allocated to more than one municipality.

Excerpt from Danbury's 2002 Plan
showing existing and proposed sewered areas

Projected demand on the sanitary sewer system has been the subject of several studies: the Comprehensive Sewerage Study (Manganaro, Martin, and Lincoln, 1967), the Sewer System Evaluation Survey, Danbury and Bethel Area (Cahn, Inc., 1983) and the Comprehensive Sewerage Study (Roald Haestad, Inc., 1987). According to Sewer Service in the Region (HVCEO, 1992), the Danbury sewage treatment plant has sufficient capacity to serve a total population of 90,000 residents.

The last study predicted that it was unlikely that the plant would ever reach full capacity by Danbury residents alone. The study also found that existing interceptors and trunk lines are generally adequate for the projected population to 2020, with the notable exception of the West Side.

Generally, priorities for the City are (1) areas with immediate problems, such as failing septic systems or existing sewers with reported overflows, and (2) areas expected to develop to a density requiring sewers. Specifically, improvement to the existing West Side system will be determined by the construction of the West Side Sewer Interceptor.

This major capital project was the subject of a 1989 study by Roald Haestad, Inc., West Side Sewer Interceptor Design Report. The study found the West Side interceptor to be required to resolve both existing capacity and flow deficiencies and to accommodate the projected increase in service demand as this part of the City is developed. All other current capital projects relating to sewer lines have less of an impact on growth than the West Side project and are primarily restricted to replacing sewage transmission lines, pumps, and equipment.

Principles for Extending Sewer Service
Expansion of the sewer service area is based on projected levels of development and density. The following principles should be followed in assessing whether a new area should be served with sewers.

1. The extension of sewer service should be seen as a method of reinforcing proposed growth patterns of the Plan of Conservation and Development, except where necessary to mitigate existing or potential pollution problems from failing on-site systems. The 1987 Comprehensive Sewerage Study warns: "If any radical change is proposed, a review of the sewer capacity should be made. Permitting high-density development for one property in a zone of lower density may take up all of the available sewer capacity and prevent development of other properties in conformance with the existing zoning. These effects are cumulative and may lead to the overloading of interceptors and trunk lines further downstream."

2. Requests for sewer service extensions within the existing service area limits should usually be approved as long as the proposed development is in accordance with existing zoning, the Plan of Conservation and Development, and other City regulations. The following concerns should be taken into consideration before granting an extension: the quality and quantity of the proposed discharge, distance from the nearest sewer, available capacity in the existing sewers between the discharge and treatment plant, additional properties that could be served by the extension, and characteristics of the proposed discharge.

3. Sewer service should not generally be extended into watersheds tributary to public water supply reservoirs, nor should development be permitted within the watersheds at densities that would require or encourage sewer service. The objective in these areas should be sewer avoidance, though there may be circumstances where extending service within the watershed will alleviate existing problems. The impact to the water supply must be evaluated and means proposed to minimize adverse impacts.

4. Requests for extensions into areas other than public water supply watersheds should be evaluated to determine the system's capacity and its ability to serve the area. The applicant will be required to fund the extension and any improvements necessary to the system to maintain the established buffer capacity, for property owners within the service limits should not be penalized by allowing outside users to absorb available capacity.

5. Areas zoned for densities of one dwelling unit or more per acre that lie outside the proposed service area boundaries and inside the water supply watershed will need to be treated on an individual basis if they create a demand for water and sewer service beyond the recommended limits. In most cases, however, the zoning of undeveloped land at such densities should not be permitted outside the service area.

6. While Lake Kenosia is not considered a primary source of water supply, its watershed is within the existing water and sewer service area limits. Additional development within the watershed should receive both water and sewer services, but such development is restricted by zoning regulations affecting Class If public water supply watersheds to prohibit or control potential sources of pollution. Expanded sewer service on the West Side within the Lake Kenosia watershed should follow a plan that focuses on both orderly service extensions and watershed protection.

Major Improvement Needs
Major improvement needs for sewer service include the following.

1. Construction of the West Side Sewer Interceptor from the Union Carbide Corporate Center to Segar Street for the purpose of providing sewer service and additional capacity to the West Side.

2. Replacement of the undersized Westville Avenue sewer to improve capacity and prevent infiltration.

3. Replacement and upgrading of aging equipment at the Mill Plain Road pump station.

4. Upgrading the sewer treatment plant to remove nitrogen and metals.

Note: The text above was taken directly from the 2002 Danbury Plan of Conservation and Development, authored by Danbury Planning Director Dennis Elpern.

A letter dated 7/1/2004 by Danbury Director of Public Works William Buckley states "With respect to sewage capacity at the treatment plant, please be advised that when the treatment plant was upgraded in the late 1980's, the City of Danbury was requested by the State Department of Environmental Protection to design and construct an additional one million gallons a day of capacity for regional needs. To date, the Town of Newtown has purchased 150,000 gallons of that extra one million and we are currently in discussions with Brookfield, Connecticut for the purchase of somewhere around 75,000 gallons per day."

The City of Danbury's sewer plant is the largest such
facility in the Region and also serves six nearby
towns. The title of this 1993 plant brochure stresses
the plant's role in regional environmental protection.

Danbury, like many other cities, first adopted the expedient of emptying its untreated sewage into the largest available river, the Still River. In time farmers, mill owners, and others downstream complained. In 1893 the State ordered Danbury to build a filtration plant for treating its sewage, an early precedent in Connecticut's water quality planning.

The history of Danbury’s sewers in modern times can be said to have begun in 1960 when the City’s Plan of Development recommended an expansion of the City’s sewer service areas. The 1967 updated Plan of Development rated the Beaverbrook area on the eastern side of Danbury as the priority area for sewer service expansion, followed by a second priority for the Danbury Airport area to the west. The plan notes that the State Water Resources Commission would not allow the construction of a separate treatment plant in the Airport area because of low stream flows in the Still River.

Accordingly, the plan to serve the Airport area required the construction of an interceptor sewer line across the City, following the course of the Still River. This sewer line was also designed to serve urban renewal development efforts Downtown. Future expansion of the sewer system was proposed for the northern and western areas of the City.

Also in 1967, a comprehensive sewerage study for Danbury was prepared by Manganaro, Martin & Lincoln. The report projected that the City’s population would increase to 77,000 persons by the year 2010, with 65,000 residents receiving municipal sewer service.

This plan suggested stringent zoning restrictions in the northwest area of the City in order to eliminate the need for municipal sewer service extensions there, and to protect the watersheds serving the City’s municipal reservoir system.

The report also suggested connections to Brookfield’s Federal Road area and Bethel’s Stony Hill area.


The comprehensive sewerage study in 1967 projected average daily flows of sewage needing treatment in 1985 at 12.5 MGD and in 2010 at 19.1 MGD. In 1969, a City referendum authorized a $9 million program of improvements to the sewerage system including increasing the sewage treatment plant’s capacity from 5.0 MGD to 12.0 MGD.

By 1974 the sewage treatment plant had been expanded and the Beaverbrook and Airport interceptor sewer lines constructed. The first regional connection to the Danbury municipal system would soon be in place via an intermunicipal agreement with Brookfield for 0.5 MGD of treatment capacity.

Interceptor sewer lines connecting to the Danbury treatment plant are generally defined as those sewers with a diameter greater than 12 inches which are used to transport collected sewage to the treatment facility.

In 1978, temporary phosphorous removal facilities were installed at the Danbury treatment plant in response to a CT DEP pollution abatement order.

In 1979, due to CT DEP imposed changes in water quality standards for concentrations of phosphorous and ammonia, pollution abatement orders were issued to both Bethel and Danbury to upgrade the quality of the treated effluent discharged from their respective sewage treatment plants. CT DEP’s motive for this action was to raise the classification of the streams receiving treated sewage effluent from a unacceptable C classification to an acceptable B classification.

A 1982 Wastewater Management Plan by Calm, Inc. proposed that Bethel and Danbury sewage systems be combined, with all Bethel sewage treated at the upgraded and expanded Danbury plant. This would result in a significant reduction in the level of nutrients entering the Still and Housatonic Rivers, also aided with the incorporation of a phosphorus removal process at the upgraded Danbury sewage treatment plant.

But one of several effluent discharge ideas raised by the City was the piping of treated sewage effluent directly to the Housatonic River so that the effluent would be diluted by the greater volume of water and thereby reduce the need to upgrade the level of treatment in the Danbury treatment plant. This idea was rejected by CT DEP.

In early 1988 CT DEP increased the approved capacity of the proposed plant renovation to 14.5 MGD. In late 1988 CT DEP directed that plant capacity be increased by an additional 1.0 MGD to 15.5 MGD in order to accommodate potential regional needs.

A 1989 report prepared for the City of Danbury by Metcalf & Eddy entitled Update to the Wastewater Management Facilities Plan -Danbury and Bethel Area. Connecticut, recommended allocating 0.7 MGD of the CT DEP’s required 1.0 MGD a potential regional needs capacity to Brookfield, and 0.3 MGD to New Fairfield.

CT DEP rejected this recommendation due to concerns that New Fairfield’s requirements for treatment could exceed the proposed 0.3 MGD allocation. Ridgefield’s current allotment of 0.14 MGD was to remain unchanged. Additional flow capacity will eventually be required in some Danbury interceptor sewer lines in order to accommodate the increased volume of sewage projected from adjacent towns.

Construction of the expanded and upgraded Danbury sewage treatment plant began in 1990 with completion scheduled for 1993, as mandated by a CT DEP order. The plant will have a CT DEP permitted treatment capacity of 15.5 MGD. As of February of 1991, CT DEP had allocated the capacity of Danbury’s treatment plant as follows:

11.8 MGD. The City's current flow is about 8.25 MGD.

2.0 MGD. Bethel currently flows (1992( .05 MGD. The estimated flow to Danbury in 1993, after abandoning its present treatment plant, is projected at 1.3 MGD.

0.8 MGD, of which 0.5 MGD is from a current agreement with Danbury and 0.3 MGD is allocated by CT DEP to Brookfield for "regional need." Brookfield currently flows 0.15 MGD to Danbury.

New Fairfield:
0.7 MGD, all of which is allocated by CT DEP as part of "regional need." There is no current flow from New Fairfield to Danbury. Sewage flows from New Fairfield to Danbury’s system would require increasing the capacity of the affected Danbury interceptor sewer lines.

0.0 MGD at present (1992), to be negotiated. Newtown has requested 0.4 MGD of Danbury capacity to serve economic development in the Hawleyville Ar ea. Ridgefield:
0.14 MGD. Ridgefield currently flows 0.09 MGD to Danbury, under an agreement for a 0.14 MGD flow cap.

CT DEP’s required 1.0 MGD "regional needs" category is distributed as follows: Brookfield 0.3 MGD; New Fairfield 0.7 MGD.

Danbury has enough surplus capacity reserved in its new sewage treatment plant to allow for a total population served of approximately 90,000 city residents, which is the saturation population possible under Danbury’s present zoning map for both sewered and non-sewered areas. The saturation population estimates also include assumptions that permit the continued economic growth of the City.

Further enlargement of the Danbury plant is restricted and possibly prohibited by the capacity of the Still River to receive the treated sewage effluent and still retain a B quality designation, as mandated by CT DEP. Any requirement for extreme purification of the sewage effluent may be more expensive than piping it directly to the Housatonic River, an old but recurring idea, where greater river flow would more effectively dilute the discharge of treated sewage effluent.

CT DEP Mandated Future Regional Needs Set-aside
CT DEP has mandated that an additional 1.0 MGD of treatment capacity be built into the upgraded Danbury treatment plant for future regional needs. This additional treatment capacity is currently allocated to New Fairfield- 0.7 MGD, and to Brookfield- 0.3 MGD. Neither municipality has agreed to pay for the CT DEP mandated allocations.

The City of Danbury, which is responsible for the maintenance and operation of the Danbury sewage treatment plant, questions the allocation of 1.0 MGD for future regional needs on the grounds that the City should not be required to pay for the construction and maintenance costs of plant capacity which has been mandated by the State to serve other municipalities.

Danbury would like to have a portion of the additional treatment capacity for future regional needs allocated to Newtown for its proposed sewer line serving the Hawleyville area. This would maintain the integrity of Danbury’s share of the treatment plant’s capacity and would provide fiscal relief to the City, with Newtown paying a prorated share of the construction and maintenance costs of the CT DEP mandated additional regional capacity.

CT DEP has indicated that it will not reallocate the additional regional capacity until it has been proven that neither Brookfield nor New Fairfield require this treatment capacity. The time frame to complete the studies required to determine the needs for sewerage treatment capacity in these communities would be mid 1993 at the very earliest.

HVCEO, Old Town Hall, 162 Whisconier Road, Brookfield, CT 06804 Tel: 203-775-6256  |  Fax: 203-740-9167  |