Geneva, NY, Tackles Stormwater Pollution
The Finger Lakes in central New York are well named. They extend like outstretched fingers downward through the middle of the state, covering an area from near Syracuse in the east to just south of Rochester, a distance of about 85 miles. The largest is Seneca Lake, more than 30 miles long, stretching from Watkins Glen on its southern tip to Geneva on its northern shore. Seneca is the deepest and widest of the Finger Lakes and is known for its excellent fishing.
Geneva likes to call itself the “Gateway to the Finger Lakes.” Tourists love the area for its natural beauty and historic sites. Fishermen enjoy the angling opportunities, and wine connoisseurs come to visit the nearby vineyards.
Keeping the lake beautiful and clean is both an environmental and economic issue for the City of Geneva. The city’s Department of Public Works recently recognized an opportunity to install a technology that would help prevent a significant amount of pollution from entering the lake. Geneva took the action proactively to protect a natural resource that is vital to the city and to this area.
Aging Infrastructure
Like many municipalities in Upstate New York, Geneva has aging infrastructure. Its sewer system is old and leaky. It has separate sanitary and storm sewers, but because of the condition of the systems, the sanitary often acts as if it were a combined sewer. Geneva’s treatment plant is designed to handle 3 million gallons per day (mgd) of wastewater, but during rainstorms it may get 10 to 12 mgd through the system due to inflow and infiltration.
 |
| Removing the CDS basket with construction equipment will reduce the volume of disposable material by 80%. |
In 2003, the New York Department of Environmental Conservation issued the City of Geneva a consent order to eliminate inflow and infiltration (I&I) into sanitary sewer systems. The mandate was for sanitary sewer lines only, but with the amount of I&I entering its systems, Geneva felt it necessary to deal with the additional problem of stormwater runoff.
Two important coincidences happened at about that time that figured prominently in Geneva’s stormwater cleanup effort. The first was a visit from Deon Lourens of CDS Technologies, who introduced the city to his company’s primary product, the Continuous Deflection Separation (CDS) unit, a device with no moving parts that uses hydraulics to remove debris and pollution from stormwater. Geneva Public Works officials read the CDS literature and third-party independent testing results and decided to invite him back to give a full demonstration. The Department of Public Works was very impressed with the effectiveness of the system and recommended that the city purchase a CDS unit to help clean up its polluted stormwater runoff. The other coincidence involved the demolition of two downtown buildings. Developers were making room for a new hotel and bank, so with the buildings out of the way, there was much easier access to the sewer collection lines buried in the lots. This would make installation easier and far less disruptive.
Installing the Stormwater Unit
The project was a collaboration between the City of Geneva’s Departments of Engineering and Public Works and CDS Technologies. CDS provided the engineering expertise. Based on its research of rainfall events and the watershed area, the company recommended a unit capable of processing 9 cubic feet per second (cfs) with an average annual total suspended solids removal efficiency of 80%, with a 10-year bypass storm flow rate of approximately 85 cfs. The city rented an excavator to dig the hole, which was approximately 20 feet in depth, and hired a crane to hoist the 10- by 17-foot concrete CDS unit into place.
The installation was relatively simple, much like putting a precast manhole in place. Crews began by cutting into the existing 48-inch-diameter storm sewer line and removing a section large enough to accommodate the weir chamber portion of the CDS unit. To tie the unit into the existing line, crews inserted PVC pipe into the brick storm sewer. This provided some structural stability to the aging brick line and made it easier to connect to the weir chamber of the unit.
 |
| The CDS bypass structure was placed and the connection completed with ductile iron pipes sleeved into the existing brick sewer. |
The CDS technology relies entirely on water hydraulics and gravity. The combined sewer flow from the sewer collection line enters a diversion chamber, where a weir guides the flow into the unit’s separation chamber. The flow creates a vortex that propels the solids and debris in a continuous motion to prevent blockage of the self-cleaning deflective screen. Water discharges outward through the screen while sediment, floatables, and solids remain in the center of the separation chamber. The trash collected either gently settles into a sump or floats to the surface where it remains until it is later removed. The stormwater, now free of debris, passes from the device and re-enters the flow heading toward the lake.
One of the benefits of Geneva performing the installation itself was the fact that the Department of Public Works employees who now maintain the system have an intimate understanding of how it works. The CDS team was always on hand to explain things as city crews performed the installation, so Geneva staff members literally know the technology from the inside out. Furthermore, it is estimated that Geneva saved about $30,000 by doing the installation itself rather than bidding the entire job out.
 |
| The CDS unit is designed to capture particles larger than 2 millimeters. |
Visible Results
The CDS unit has been in place two years now, and in that time the city has cleaned the sump chamber twice. The unit was designed with a basket in the sump that can be lifted out with a front-end loader and emptied into a dump truck. It is amazing to see the volume of debris that used to end up in the lake—polystyrene, cigarette butts, paper cups, plastic, aluminum cans, and organic matter are just some of what has been found in the unit so far.
Anyone who studies stormwater runoff knows that a lot of petroleum-and carbon-based pollution also washes off the streets in a rainfall event. At the suggestion of CDS Technologies, Geneva put sorbents—pellets that absorb chemicals—into the unit. As a result, the city is removing both suspended solids and nasty chemical pollution. The result is an environmentally healthier lake.
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The City of Geneva has been so pleased with the outcome of this project that it is looking at installing similar units on its other main sewer lines. The city also is making it a requirement that developers install stormwater cleaning devices on any new construction near the lakefront. One developer recently took the city’s advice and installed a smaller CDS unit to clean the stormwater that runs off the parking lot of the new bank.
It is easy to see the effect of Geneva’s stormwater project every time the basket is emptied from the cleaning unit. It is a wonderful feeling to know that Seneca Lake is cleaner now than before. While this is only the first step in the city’s efforts to clean up stormwater runoff, it is a step that exceeded its expectations. Geneva is encouraged to do more so that future generations of New Yorkers will enjoy the benefits of a clean, healthy Seneca Lake.
Author's Bio: William Grove, P.E., is the deputy director of Engineering and Public Works for Geneva, NY.
March-April 2007
Geneva, NY, Tackles Stormwater Pollution
The Finger Lakes in central New York are well named. They extend like outstretched fingers downward through the middle of the state, covering an area from near Syracuse in the east to just south of Rochester, a distance of about 85 miles. The largest is Seneca Lake, more than 30 miles long, stretching from Watkins Glen on its southern tip to Geneva on its northern shore. Seneca is the deepest and widest of the Finger Lakes and is known for its excellent fishing.
Geneva likes to call itself the “Gateway to the Finger Lakes.” Tourists love the area for its natural beauty and historic sites. Fishermen enjoy the angling opportunities, and wine connoisseurs come to visit the nearby vineyards.
Keeping the lake beautiful and clean is both an environmental and economic issue for the City of Geneva. The city’s Department of Public Works recently recognized an opportunity to install a technology that would help prevent a significant amount of pollution from entering the lake. Geneva took the action proactively to protect a natural resource that is vital to the city and to this area.
Aging Infrastructure
Like many municipalities in Upstate New York, Geneva has aging infrastructure. Its sewer system is old and leaky. It has separate sanitary and storm sewers, but because of the condition of the systems, the sanitary often acts as if it were a combined sewer. Geneva’s treatment plant is designed to handle 3 million gallons per day (mgd) of wastewater, but during rainstorms it may get 10 to 12 mgd through the system due to inflow and infiltration.
|
| Removing the CDS basket with construction equipment will reduce the volume of disposable material by 80%. |
In 2003, the New York Department of Environmental Conservation issued the City of Geneva a consent order to eliminate inflow and infiltration (I&I) into sanitary sewer systems. The mandate was for sanitary sewer lines only, but with the amount of I&I entering its systems, Geneva felt it necessary to deal with the additional problem of stormwater runoff.
Two important coincidences happened at about that time that figured prominently in Geneva’s stormwater cleanup effort. The first was a visit from Deon Lourens of CDS Technologies, who introduced the city to his company’s primary product, the Continuous Deflection Separation (CDS) unit, a device with no moving parts that uses hydraulics to remove debris and pollution from stormwater. Geneva Public Works officials read the CDS literature and third-party independent testing results and decided to invite him back to give a full demonstration. The Department of Public Works was very impressed with the effectiveness of the system and recommended that the city purchase a CDS unit to help clean up its polluted stormwater runoff. The other coincidence involved the demolition of two downtown buildings. Developers were making room for a new hotel and bank, so with the buildings out of the way, there was much easier access to the sewer collection lines buried in the lots. This would make installation easier and far less disruptive.
Installing the Stormwater Unit
The project was a collaboration between the City of Geneva’s Departments of Engineering and Public Works and CDS Technologies. CDS provided the engineering expertise. Based on its research of rainfall events and the watershed area, the company recommended a unit capable of processing 9 cubic feet per second (cfs) with an average annual total suspended solids removal efficiency of 80%, with a 10-year bypass storm flow rate of approximately 85 cfs. The city rented an excavator to dig the hole, which was approximately 20 feet in depth, and hired a crane to hoist the 10- by 17-foot concrete CDS unit into place.
The installation was relatively simple, much like putting a precast manhole in place. Crews began by cutting into the existing 48-inch-diameter storm sewer line and removing a section large enough to accommodate the weir chamber portion of the CDS unit. To tie the unit into the existing line, crews inserted PVC pipe into the brick storm sewer. This provided some structural stability to the aging brick line and made it easier to connect to the weir chamber of the unit.
|
| The CDS bypass structure was placed and the connection completed with ductile iron pipes sleeved into the existing brick sewer. |
The CDS technology relies entirely on water hydraulics and gravity. The combined sewer flow from the sewer collection line enters a diversion chamber, where a weir guides the flow into the unit’s separation chamber. The flow creates a vortex that propels the solids and debris in a continuous motion to prevent blockage of the self-cleaning deflective screen. Water discharges outward through the screen while sediment, floatables, and solids remain in the center of the separation chamber. The trash collected either gently settles into a sump or floats to the surface where it remains until it is later removed. The stormwater, now free of debris, passes from the device and re-enters the flow heading toward the lake.
One of the benefits of Geneva performing the installation itself was the fact that the Department of Public Works employees who now maintain the system have an intimate understanding of how it works. The CDS team was always on hand to explain things as city crews performed the installation, so Geneva staff members literally know the technology from the inside out. Furthermore, it is estimated that Geneva saved about $30,000 by doing the installation itself rather than bidding the entire job out.
|
| The CDS unit is designed to capture particles larger than 2 millimeters. |
Visible Results
The CDS unit has been in place two years now, and in that time the city has cleaned the sump chamber twice. The unit was designed with a basket in the sump that can be lifted out with a front-end loader and emptied into a dump truck. It is amazing to see the volume of debris that used to end up in the lake—polystyrene, cigarette butts, paper cups, plastic, aluminum cans, and organic matter are just some of what has been found in the unit so far.
Anyone who studies stormwater runoff knows that a lot of petroleum-and carbon-based pollution also washes off the streets in a rainfall event. At the suggestion of CDS Technologies, Geneva put sorbents—pellets that absorb chemicals—into the unit. As a result, the city is removing both suspended solids and nasty chemical pollution. The result is an environmentally healthier lake.
The City of Geneva has been so pleased with the outcome of this project that it is looking at installing similar units on its other main sewer lines. The city also is making it a requirement that developers install stormwater cleaning devices on any new construction near the lakefront. One developer recently took the city’s advice and installed a smaller CDS unit to clean the stormwater that runs off the parking lot of the new bank.
It is easy to see the effect of Geneva’s stormwater project every time the basket is emptied from the cleaning unit. It is a wonderful feeling to know that Seneca Lake is cleaner now than before. While this is only the first step in the city’s efforts to clean up stormwater runoff, it is a step that exceeded its expectations. Geneva is encouraged to do more so that future generations of New Yorkers will enjoy the benefits of a clean, healthy Seneca Lake.