Saturday
Stormwater Consultant Makes Presentation to Town Board
July 14, 2007. Last Monday night the drainage consultants presented their findings to the Town Board. After reviewing their project's scope and the area's hydrology and hydrogeology, the consultants went on to make a number of conclusions and recommendations. The conclusions from the written report and presentation include:
* "Piped drainage system may alleviate some surface flooding; not basement flooding and saturation."
* "Groundwater levels are not likely increasing, but may be fluctuating more than in the past due to changes in precipitation and increases in imperviousness."
The consultants made a number of recommendations regarding Briarwood II:
* "Lots 58, 67, and 70 should be eliminated due to the extraordinary encumbrance presented by the sewer and water easement" (p. 36).
* "Eliminate Lot 66 and use for post development stormwater management."
* "Minimize impervious surfaces."
* "Maintain soil thickness over fragipan."
* "Mitigate to the extent possible increases in runoff volume."
* "Given the geology of the area, it will not likely be possible to fully mitigate the volumetric increases but even addressing a portion of the volume would be beneficial" (p. 37).
* "Test pits should be performed to determine if the soils below the fragipan layer have the potential to provide infiltration of stormwater" (p. 37).
In addition, several recommendations were made regarding the hydrologic analysis:
* "Modify the hydrologic analysis for the Briarwood II development to incorporate the full tributary watershed and provide for a common analysis point suitable for evaluating downstream impacts. The New York State Stormwater Management Design Manual suggests that downstream analysis be completed for developments over 50 acres in size; however, given the flood prone nature of the area downstream of Briarwood II it is our opinion that a more rigorous analysis should be completed" (p. 37).
* "Modify analysis to reflect saturated ground conditions."
* "Modify analysis to reflect increased rainfall depths."
The Town Board appeared receptive to these recommendations. Members of the board expressed a desire to see Briarwood II's stormwater analysis reflect the full volume of stormwater flowing downstream rather than peak flow only.
The Ithaca Journal and Ithaca Times both published articles covering this presentation.
* "Piped drainage system may alleviate some surface flooding; not basement flooding and saturation."
* "Groundwater levels are not likely increasing, but may be fluctuating more than in the past due to changes in precipitation and increases in imperviousness."
The consultants made a number of recommendations regarding Briarwood II:
* "Lots 58, 67, and 70 should be eliminated due to the extraordinary encumbrance presented by the sewer and water easement" (p. 36).
* "Eliminate Lot 66 and use for post development stormwater management."
* "Minimize impervious surfaces."
* "Maintain soil thickness over fragipan."
* "Mitigate to the extent possible increases in runoff volume."
* "Given the geology of the area, it will not likely be possible to fully mitigate the volumetric increases but even addressing a portion of the volume would be beneficial" (p. 37).
* "Test pits should be performed to determine if the soils below the fragipan layer have the potential to provide infiltration of stormwater" (p. 37).
In addition, several recommendations were made regarding the hydrologic analysis:
* "Modify the hydrologic analysis for the Briarwood II development to incorporate the full tributary watershed and provide for a common analysis point suitable for evaluating downstream impacts. The New York State Stormwater Management Design Manual suggests that downstream analysis be completed for developments over 50 acres in size; however, given the flood prone nature of the area downstream of Briarwood II it is our opinion that a more rigorous analysis should be completed" (p. 37).
* "Modify analysis to reflect saturated ground conditions."
* "Modify analysis to reflect increased rainfall depths."
The Town Board appeared receptive to these recommendations. Members of the board expressed a desire to see Briarwood II's stormwater analysis reflect the full volume of stormwater flowing downstream rather than peak flow only.
The Ithaca Journal and Ithaca Times both published articles covering this presentation.
