Introduction:

In order to reduce the amount of pollution entering Lake Mamanasco by means of storm water runoff, a "Lake Protection Zone" has been delineated within the lake's watershed. The zone will has two regions. Region #1 comprises the shoreline and a shoreline buffer, which  constitutes the area from the shoreline to a distance 100' upland from the lake margin. Region #2 comprises all of the remaining area within the watershed beyond the 100' point.

As is currently the case with the four rivers in Town, the Ridgefield Inlands Wetlands Board has amended the Inland-Wetlands regulations by increasing the Upland Review area around Mamanasco Lake to 100 feet and by adopting a set of guidelines that are recommended for the use throughout the entire watershed.  Any regulated activity that takes place within 100' of the lake shoreline will require a permit from the Inlands Wetlands Board.  The guidelines may, at the discretion of the Inland Wetlands Board or its designated agents, be required as condidtions to obtain a permit for a regulated activity not only within the 100' review area but within the entire watershed.  The guidelines are presented below in detail.  They are consistent with the ongoing efforts of MLIF to protect the health of the lake.  Lake systems such as Mamanasco are equally susceptible to land use impacts and are worthy of the same protection as the rivers.

Since Region #1 is more densely developed it is the most critical in terms of the impact on the water quality. With the 25’ extended upland review area, all of the land use in Region #1 will be regulated under Section 4.5 of the Town's Inland Wetland and Watercourses regulations. The the guidelines are defined in this document under Lake Protection Guidelines – Region #1. (Note: The use of guidelines has proven to be effective in other towns and, with proper oversight, will be effective in the Town of Ridgefield as well.)

Under the proposed changes, land in Region #2 that is within 100’ of a watercourse will also be subject to Inland Wetland regulations. The guidelines are defined in this document under Lake Protection Guidelines – Region #2. 

Background and Rational:

Lake Mamanasco has undergone advanced cultural eutrophication, due primarily to stormwater and groundwater inputs from the 537-acre watershed.  A study conducted by Baystate Environmental in 1991, stated the primary source of phosphorus identified was the storm drainage system (50% of the total), with both groundwater (24%) and surface tributaries (16%) contributing substantial amounts of this limiting nutrient to the lake. 

A 50% reduction in phosphorus loading from the contributing watershed was recommended in the Baystate findings to improve lake water quality.  In 1996 the Mamanasco Lake Improvement Fund (MLIF) adopted this goal and in association with the Town of Ridgefield and the Connecticut Department of Environmental Protection (CT DEP) implemented a plan to reduce the introduction of sediment and phosphorus by the installation of Best Management Practices (BMPs) on a prioritized basis within the lake’s watershed. 

Land-Tech Consultants was retained to develop a watershed management plan for Lake Mamanasco.  The objectives of this project were to assess current watershed conditions, identify nonpoint source pollutants, and the design and development of a stormwater and sediment management plan for the drainage area on the western side of the lake. 

A final report entitled Watershed Management Plan for Mamanasco Lake Phase I Report December 29, 1997 identified a prioritized grid system approach to reduce sediment loads and associated phosphorus contributions to the lake. The Mamanasco Lake Improvement Fund adopted the recommendations and Land-Tech Consultants were contracted to begin design of the control measures. Design and construction of Best Management Practices (BMP’s) to reduce nutrient loading from stormwater runoff and sedimentation began in 1998 and 2001, respectively with Grid #1 at Second Lane. Following recommendations from the Connecticut Department of Environmental Protection (CTDEP) design and construction of BMP’s are completed within lower (i.e., Mamanasco Road) and then the upper reaches of individual subsheds (drainage areas) of each grid. The Mamanasco Lake Improvement Fund with grants from the Town of Ridgefield and the CTDEP, Clean Lakes Program, provide funding for design and construction. The Town of Ridgefield Engineering Department contracts for and oversees construction of the drainage improvements. Maintenance of the BMP’s is provided by the Town’s Highway Department.

The MLIF recognizes that continued reduction of diffuse nonpoint water contamination requires a watershed-based approach, and that the majority of water quality problems result from nonpoint sources are associated with urbanization of the watershed among other sources. The introduction of pollutants (sediment, nutrients, pesticides, etc.) varies spatially and temporally, making quantification and control difficult.

The National Water-Quality Assessment (NAWQA) initiated in 1991 by the U.S. Geological Survey, confirmed that water-quality conditions and aquatic health are reflective of a complex interaction of land-use and management and natural resources (i.e., soils, geology, hydrology and climate). The EPA Storm Water Phase II Rule originates from the National Pollutant Discharge Elimination System (NPDES) and applies to communities like Ridgefield, which has adopted a Phase II storm water management plan; also recognizes the importance of controlling non-point source pollution from stormwater runoff. The state of Connecticut also recognizes the importance of managing the introduction nonpoint source pollutants into wetlands and watercourses by the adoption of Inland wetlands and watercourses regulations and 2002 Connecticut Guidelines for Soil Erosion and Sediment Control. The Town of Ridgefield implements both regulatory programs.

Recognizing the importance of protecting the lake’s water quality and the results of the Baystate D/F report findings, MLIF proposed adoption of a Lake Protection Zone to further reduce pollutant loading of the lake and expand the introduction of BMPs on both developed and undeveloped parcels as well as within publicly held land.

Goals and Objectives:

The following goals and objectives are included in the Lake Protection Zone:

Goals:

1. The control and reduction of sediment and associated nutrients (phosphorus) from watershed runoff;
2. Maximize, to the extend possible, the infiltration of runoff associated with urbanization of the watershed;
3. Complement existing land use regulations, while permitting the reasonable use of developed and undeveloped land within the Lake’s watershed, and;
4. Education of the populous living within the watershed and those who use the lake to the impacts associated with land-development and land use.

Objectives.

1. Establishment of management zones around the lake with specific guidelines to help direct land development and use;
2. Introduction of vegetative and structural BMPs to control and treat stormwater runoff on both developed and undeveloped watershed land;
3. Use of the most current BMP’s to remove, to the maximum extent possible, nonpoint source pollutants when upgrading municipal stormwater management systems or public rights of way;
4. Control and treat the peak rate of post-development stormwater runoff for a two –year storm to pre-development rates;
5. Establish a twice per year (fall and spring) cleaning requirement of municipally owned, operated and controlled stormwater management systems, and;
6. An annual inspection of the watershed by the MLIF in association with the Town of Ridgefield to identify existing or new sources of nonpoint pollution and take measures to control them.

PROPOSED GUIDELINES

for the

PROTECTION OF MAMANASCO LAKE

Regions of Lake Watershed Protection:

Region #1 - Shoreline and Shoreline Protection Area, which includes the lake surface to a point 100.0 ft landward, and;

Region #2 - The remainder of the watershed beyond Region #1

Land Development Criteria- Existing and Undeveloped Land

The following guidelines for lake water quality protection are developed from a review of the literature and land use practices employed by other communities.  They include both Regions #1 and #2. Land use guidelines for each area are presented below.  

LAKE PROTECTION GUIDELINES – Region #1

Shoreline and Shoreline Protection Area

Region #1 is the most critical and most developed; therefore, having the greatest potential to impact on lake water quality. The primary objectives within this area on both developed and undeveloped parcels are the creation of a vegetative littoral zone (0 - 3 feet in depth) and upland buffer to filter surface runoff before it enters the lake.  See Figures No. 2 & 3 for a typical site plan examples. To achieve this, the following is proposed.

1.      A dock (floating or fixed) and beach area is permitted. The beach area should not exceed 25% of the parcel’s lake frontage.

2.      On undeveloped parcels, a 10.6-meter (35 ft.) wide minimum vegetative buffer component consisting of 50% coarse grasses, wildflowers or other acceptable herbaceous growth and 50% shrubs and trees is proposed.

3.      If a clearing is made for lake access through a vegetative buffer, a path 4-6’ in width made at an angle through the vegetative buffer would decrease the likelihood of runoff. The surface of the path should be porous (i.e., wood chips, stone dust, gravel or other acceptable pervious non-polluting material).

4.      On any existing developed parcel the same 10.6-meter wide buffer is recommended.  When site restrictions preclude this from being achieved, a 4.5-meter (15 ft.) wide minimum upland vegetative buffer component consisting of 50% coarse grasses, wildflowers or other acceptable herbaceous growth and 50% shrubs and trees is recommended.

5.      On existing developed parcels where site conditions preclude the creation of a 4.5-meter wide vegetative upland buffer, one-third or five (5) feet of the buffer may consist of aquatic emergents planted in the shallow littoral (normal high water mark to a 3 foot depth) of the lake.

6.      Clearing of vegetation for a view corridor should be limited to 25% of a parcel’s shoreline length. It is recommended that clear cutting of vegetation on individual lots be limited to a maximum of 25% of the lot area.

7.      Vertical clearing of vegetation should be limited to one-third the height of the tree canopy.

8.      It is recommended that walkways, docks, beaches and boathouse be developed in the view corridor.

9.      It is recommended that landowners employ current Best Management Practices (see attached BMPs) to control sediment and erosion  consistent with the Connecticut guidelines

10.  Control post-development peak rate of stormwater runoff to predevelopment rates for a 2-year storm. Infiltration is the preferred method for control, but other methods may be acceptable. No direct discharges of stormwater runoff to the lake are permitted without pre-treatment to remove 80% of the total suspended solids (TSS) contained in the runoff.

LAKE PROTECTION GUIDELINES – Region #2

1.      It is recommended that clear cutting of vegetation on individual lots be limited to a maximum of 25% of the lot area.

2.      It is recommended that clearing of natural vegetation (native species of trees shrubs and herbaceous plants) on individual lots be limited to a maximum of 75% of the lot area. Use of native plant species for landscaping is encouraged.

3.      It is recommended that impervious coverage be kept to a maximum of 8%. Impervious area (i.e., roof, drives, concrete patios) in excess of 8% of the lot area should where practical, be controlled to predevelopment rates for a 2-year storm.  Infiltration is the preferred method for control, but other methods may be acceptable. No direct discharges of stormwater runoff to stormwater systems are permitted without pre-treatment to remove 80% of the TSS. 

4.      An 8-meter (26 ft) wide minimum upland vegetative buffer component consisting of 50% coarse grasses, wildflowers or other acceptable herbaceous growth and 50% shrubs and trees should be provided adjacent to all wetlands and watercourses. Site conditions (e.g., steep slopes) may warrant greater vegetative buffer widths.

Additional Recommendations for Entire Watershed – Guidelines

Improvements to infrastructure like roadways and drainage systems

• Employ current BMP’s for upgrading storm water systems consistent with the Connecticut guidelines.
• Cleaning of catch basins, large particle separators, plunge pools, etc., once per year in Region #2 and twice per year (fall and spring) within Region #1.

Turf Grass Management

• Testing of topsoil from at least 40% of developed parcels every three to five years to make homeowners aware if excessive fertilization is occurring. The goal is a more judicious use of fertilizer to reduce the amount of nitrogen and phosphorous entering the lake.

Note: Soil samples to be collected from higher priority areas first and sampling staggered, annually from Region #1 then to Region #2. Connecticut Agricultural Station will analyze samples free of charge. 

Septic System Maintenance

• It is recommended that septic tanks be cleaned by a licensed septic cleaner every three to five years.
• File report with health department to renew discharge permit.  

Riparian Buffers

·         Develop five (5) meter wide (16.4 feet) riparian buffer at a minimum wherever possible.

Entire Watershed

1.                  Subdivisions of two or more lots should comply with current Subdivision regulations for pre and post development peak rates of runoff.

2.                  On-site sewage disposal systems should comply with current State and Town of Ridgefield Health codes.  In situations where existing site limitations preclude meeting the current standards, every effort should be made to comply, including the use of innovative and alternative sewage disposal methodologies approved by the State of Connecticut, Department of Health and Addiction Services.

3.                  Erosion and sediment control plans should be prepared in accordance with current State Guidelines for all land alteration activities regardless of the area of disturbance.

Implementation

The Town of Ridgefield Inland Wetlands and Watercourse Agency regulates land use activities within the Town’s inland wetlands and watercourses and the upland review area associated with these resources under Section 4.5 of their regulations. Current Inland wetland regulations provide additional protection of named waterways within the community. Lake systems such as Mamanasco Lake are equally susceptible to land use impacts and are worthy of additional protection. Thus, implementation of these Guidelines is proposed through the Town of Ridgefield Inland Wetlands and Watercourses agency as part of the existing permitting process.