CGP FAQs - Coverage in Impaired Watersheds
The 303(d) list of impaired waters contains many brooks in the City of South Burlington, including Potash Brook and Bartlett Brook. As much of the City's expansion lies in these watersheds, LHINC has started to encounter stricter permitting requirements for projects in these areas. As part of my CGP FAQ series, I have outlined the primary differences between a standard CGP and an Individual Discharge Permit.
Nomenclature
First, the permit that you get is not a "CGP", technically. The "G" in CGP stands for general, and that means it's a blanket permit that you ask for. There is no general permit for working in impaired waters. The permits have to be written the old fashioned way, by an individual permit for each project. This usually means more time in review by the Stormwater Section.
5 acres open at one time
The first primary difference is the amount of area that is exposed at one time. There are no limits, per se, in how much land is open in a CGP (within reasonable limits, of course). The individual permit is different in that only 5 acres can be open at one time. This means that for larger projects, creative phasing must be used. For example, take road construction. Instead of grubbing away all the topsoil, laying out all the utilities, then following up with the gravel base course, work could proceed incrementally. The topsoil would be stripped to a few hundred feet ahead of utility installation, and the gravel could be laid down as utilities are completed. Since gravel is considered a stabilized surface, it doesn't count towards your 5-acre limit. Techniques like this are key especially in the winter, since the limit on open earth is reduced even further to one acre. In this case, it may be necessary to limit construction to buildings only. A stone pad around the perimiter of the building will prevent sedimentation when the spring thaw comes, and the area won't be considered to be disturbed.
Detailed Construction Sequence
The CGP allows for a generalized construction sequence, but a more specific timetable is required for an Individual Permit. Estimates of how long each task (e.g. clearing and grubbing, utility installation, house construction) will take must be detailed, and any places where concurrent activity would expedite the process should be used. A Gantt chart is often used to effectively present this information.
Turbidity Monitoring Plan
The Turbidity Monitoring Plan (TMP) works to give a yardstick to measure the Erosion Prevention and Sediment Control (EPSC) Plan's effectiveness. The TMP is performed by an independent Environmental/Engineering Specialist. A set of reference and assessment sample points measure the sediment level in upstream (reference) and downstream (assessment) locations. The measure of sediment levels is determined with an NTU meter. If NTU levels between reference and assessment points is greater than 10 units, and additional sample is sent to an environmental lab for total suspended solids (TSS) analysis. A TSS level of >200 triggers a meeting between all parties (State, developer and Environmental Specialist).
It is beneficial to have some data on hand before construction starts. Turbidity monitoring is not an exact science (NTU readings are tricky to get a precise idea of the sediment load in a water body), and it is possible for the site as it exists currently to exceed the 10 NTU threshold. A baseline of data proving this helps to more fully explain the characteristics of the water body.
Longer Public Notice Period
The typical CGP public notice period is ten days. For an individual permit, that notice period is extended to thirty days.
These are the main differences between the two levels of permit coverage. Depending on the site location and its potential sensitivity, the State may have more requirements.
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Nomenclature
First, the permit that you get is not a "CGP", technically. The "G" in CGP stands for general, and that means it's a blanket permit that you ask for. There is no general permit for working in impaired waters. The permits have to be written the old fashioned way, by an individual permit for each project. This usually means more time in review by the Stormwater Section.
5 acres open at one time
The first primary difference is the amount of area that is exposed at one time. There are no limits, per se, in how much land is open in a CGP (within reasonable limits, of course). The individual permit is different in that only 5 acres can be open at one time. This means that for larger projects, creative phasing must be used. For example, take road construction. Instead of grubbing away all the topsoil, laying out all the utilities, then following up with the gravel base course, work could proceed incrementally. The topsoil would be stripped to a few hundred feet ahead of utility installation, and the gravel could be laid down as utilities are completed. Since gravel is considered a stabilized surface, it doesn't count towards your 5-acre limit. Techniques like this are key especially in the winter, since the limit on open earth is reduced even further to one acre. In this case, it may be necessary to limit construction to buildings only. A stone pad around the perimiter of the building will prevent sedimentation when the spring thaw comes, and the area won't be considered to be disturbed.
Detailed Construction Sequence
The CGP allows for a generalized construction sequence, but a more specific timetable is required for an Individual Permit. Estimates of how long each task (e.g. clearing and grubbing, utility installation, house construction) will take must be detailed, and any places where concurrent activity would expedite the process should be used. A Gantt chart is often used to effectively present this information.
Turbidity Monitoring Plan
The Turbidity Monitoring Plan (TMP) works to give a yardstick to measure the Erosion Prevention and Sediment Control (EPSC) Plan's effectiveness. The TMP is performed by an independent Environmental/Engineering Specialist. A set of reference and assessment sample points measure the sediment level in upstream (reference) and downstream (assessment) locations. The measure of sediment levels is determined with an NTU meter. If NTU levels between reference and assessment points is greater than 10 units, and additional sample is sent to an environmental lab for total suspended solids (TSS) analysis. A TSS level of >200 triggers a meeting between all parties (State, developer and Environmental Specialist).
It is beneficial to have some data on hand before construction starts. Turbidity monitoring is not an exact science (NTU readings are tricky to get a precise idea of the sediment load in a water body), and it is possible for the site as it exists currently to exceed the 10 NTU threshold. A baseline of data proving this helps to more fully explain the characteristics of the water body.
Longer Public Notice Period
The typical CGP public notice period is ten days. For an individual permit, that notice period is extended to thirty days.
These are the main differences between the two levels of permit coverage. Depending on the site location and its potential sensitivity, the State may have more requirements.
