Chazen Engineering Comments THE
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Engineers Hudson Valley Office (845)454-3980
Land Surveyors Capital District Office (518) 273-0055
Planners
Environmental Professionals
Landscape Architects
February 09, 2017
Mr. Craig Brown
Zoning Administrator and Code Compliance Officer
Town of Queensbury
742 Bay Road
Queensbury, New York 12804
Delivered via email only: CraigB@gueensbury.net
Re: Scoville Mini-Storage Facility
Town of Queensbury, Warren County, New York
Chazen Project#91700.04
Queensbury Ref#SP11-2017
Dear Mr. Brown:
The Chazen Companies (Chazen) has received a submission package from your office for the above
referenced project. The applicant intends to construct a self-storage facility consisting of five buildings
on a 3.26 acre parcel that is to be subdivided. Submitted information includes the following:
• Site Plans and Details prepared by Vision Engineering, LLC,January 15, 2017;
• Stormwater Pollution Prevention Plan prepared by Vision Engineering, LLC, dated January 15,
2017; and,
• Site Plan Review Application, Full EAF, supporting documentation, and Project Narrative dated
January 13, 2017.
Your office has requested that we limit our review to the design of stormwater management and
erosion and sediment control items as it relates to compliance to local, state or relevant
codes/regulations and general practice. Based upon our review, Chazen offers the following comments
for the Town's consideration:
Stormwater Management& Erosion and Sediment Control:
1. The project proposes to disturb an area of 2.5 acres and requires the preparation of a
Stormwater Pollution Prevention Plan (SWPPP) in accordance with GP-0-15-002 that includes
erosion and sediment controls as well as post construction stormwater management practices.
A Stormwater Pollution Prevention Plan (SWPPP) has been provided. Comments relating to the
Stormwater Management Report and SWPPP are offered below.
2. Section 179-6-080 of the Town Code, states that stormwater drainage plans shall analyze the
impacts of a project using at least a 50-year return interval storm with regards to both runoff
Chazen Engineering, Land Surveying&Landscape Architecture Co., D.P.C.
Chazen Environmental Services, Inc.
The Chazen Companies, Inc.
Town of Queensbury
Scoville Mini-Storage Facility
February 09,2017
Page 2
rate and volume for commercial projects. Section 179-6-080 prescribes that stormwater
management be designed so that post-development runoff rates and volumes are equal to or
less than pre-development runoff.
3. The Applicant has consulted with the NYSDEC regarding the onsite wetlands. It appears the
latest correspondence was from January 12, 2017 in which Kevin Bliss (NYSDEC) has requested
two modifications to the plans.The Applicant should clarify that the modifications were made to
the plans in respect to the January 12, 2017 letter.
4. The Pre-Development Runoff Rate table in section 3.5 of the SWPPP does not match the
HydroCAD model results. The Applicant to revise accordingly.
5. Typically, the overall watershed boundary should not be limited to the subject property line; it
shall include the entire watershed tributary to each subcatchment/design point. Pursuant to this
the Applicant should revise the boundaries appropriately or provide additional topographical
information validating the subcatchments depicted.
6. The stormwater runoff rate and volume requirements (both the Town's and the SPDES GP) are
not satisfied as depicted in the Applicant's pre-development and post-development rate and
volume tables presented in the SWPPP.
For instance, the Town's code requires no increase in runoff volume and rate for the 50-year 24-
hour storm compared to the pre-development condition. At Design Point 2 the predevelopment
50-year rate is 2.18 cfs and the volume is 0.187 acre-feet; the post-development 50-year rate is
6.70 cfs and the volume is 0.800 acre-feet. The rate and volume both increase in the post-
development condition.
The SPDES General Permit requires no increase in stormwater runoff rate for the 100-year 24-
hour condition. At Design Point 2 the predevelopment rate is 2.85 cfs and the post-development
rate is 7.41 cfs.
The increase in rates and volume appears to be issue with how the design points were chosen. It
appears that Design Point 1 and Design Point 2 both discharge to the existing adjacent wetland
located to the east of the site. The Applicant should clarify if these are distinct design points and
the Applicant shall revise the SWPPP to ensure conformance to the Town's and SPDES rate and
volume requirements.
7. The infiltration trench in the HydroCAD model depicts the exfiltration at a depth of 0.00'. The
Applicant shall revise the exfiltration depth to be the bottom of the facility.
8. The Infiltration Trench worksheet states that the "storage volume above the floor" is the
pretreatment technique utilized and the worksheet states that inadequate pretreatment is
provided. The site plan does not depict a storage volume above the floor; the Applicant to
clarify. The eave trench detail on sheet C-9 depicts a 3" pea gravel filter layer, the Applicant to
clarify if the pea gravel layer is intended for pretreatment?
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Town of Queensbury
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February 09,2017
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It is noted that Section 6.3.3 of the NYS SMDM considers an upper sand layer (6" minimum with
filter fabric at the sand/gravel interface) acceptable pretreatment for infiltration trenches.
9. Regarding Overbank Flood Control Criteria (Section 4.5 of the NYS SMDM), for slopes greater
than 1% (average slope) the maximum sheet flow distance for Tc calculations is 150 feet for
predevelopment conditions and 100 feet for post development conditions; the maximum
distance is extended to 250 feet for predevelopment conditions and 150 feet for post-
development conditions for average slopes less than 1%. Regarding Stream Channel Protection
Volume requirements (Section 4.4 of the NYS SMDM), the length of sheet flow used in Tc
calculations is limited to no more than 100 feet for post development conditions.
Existing subcatchment EDP-1 lists a sheet flow of 300 feet (1.7% slope), EDP-2 lists a sheet flow
of 250 feet (1.3% slope), and EDP-3 lists a sheet flow of 215 feet (2.3% slope); the Applicant to
revise to conform to the design criteria of Section 4 of the NYS SMDM.
The proposed subcatchments that do not meet the design criteria of Section 4 of the NYS SMDM
shall be revised (subcatchments P1, P3, P4) as well.
10. The Applicant submitted a blank NOI, the Applicant to submit a completed draft NOI with the
next submission.
11. According to the Applicant's Runoff Reduction Volume spreadsheet, the proposed design is
intended to used dry swales as a Standards SMP with RRv capacity. These swales are labeled as
VS1, VS2, and VS3 on the site plan sheets. The dry swales are not modeled in the HydroCAD
model; the Applicant shall model the dry swales and any features intended to create ponding in
the dry swale.
The dry swale worksheets provided in the SWPPP do not entirely match the site plans. The dry
swale worksheets state that checkdams are provided to meet the 10% WQv pretreatment
requirement, however permanent check dams are not depicted on the plans; the Applicant to
revise accordingly.
It is unclear how the dry swales temporarily store the WQv as prescribed in Section 6.5.4 of the
NYS SMDM. The Applicant to revise the design to ensure the requirements of Section 6.5.4 are
met.
12. The Permanent Stormwater Device Maintenance Section 10.4 shall be revised to include the
maintenance procedures prescribed for Dry Swales in Section 6.5.6 of the NYS SMDM.
13. The swale detail on sheet C-8 does not conform to the dry swale requirements of the NYS
SMDM. Section 6.5.2 of the NYS SMDM states, "An underdrain system shall be used in the dry
swale to ensure this ponding time." The Applicant to revise the detail to conform to Section
6.5.2.
14. Section 6.5.7 of the NYS SMDM states the cold-climate considerations for dry swales. It is
unclear if these considerations are proposed for the dry swale; the Applicant to clarify. For
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Town of Queensbury
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February 09,2017
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instance, the Snowmelt Infiltration on Frozen Ground and Culvert Freezing considerations do
not appear to be incorporated in the design.
15. Section 6.2.3 of the NYS SMDM prescribes the treatment requirements for stormwater
wetlands. The SM DM states, "At least 25%of the WQv shall be in deepwater zones with a depth
greater than four feet. A forebay shall be located at the inlet, and a four to six foot deep
micropool that stores approximately 10%of the WQv shall be located at the outlet to protect the
low flow pipe from clogging and prevent sediment resuspension."
The micro-pool outlet is not included in the HydroCAD model and therefore difficult to
determine the volume stored in the micro-pool outlet. The Applicant shall add the micro-pool
outlet to the HydroCAD model. The Applicant shall revise the design to ensure at least 25% of
the WQv is in the deepwater zones with a depth greater than four feet.
16. It does not appear that the landscaping plan indicates the methods and the planting plan for the
proposed stormwater wetland. The Applicant shall revise the landscaping plan to ensure
conformance with Section 6.2.4 of the NYS SMDM.
17. Section 6.2.4 of the NYS SMDM states, "A wetland plant buffer must extend 25 feet outward
from the maximum water surface elevation, with an additional 15 foot setback to structures."
The Applicant shall revise the site plans to depict both the plant buffer and additional setback to
structures.The Applicant shall ensure the buffer meets the requirements of Section 6.2.4.
18. The Applicant to provide the elevation at which stormwater within the proposed wetland would
flow into the micro-pool outlet area. The Applicant has indicated in the Scoville SWPPP
Calculations that the proposed wetland pond WQv is provided at an elevation of 308.9'; the
Applicant to clarify how this elevation was determined.
19. The contractor / subcontractor certification statement does not match the most current
statement, which is provided in Part III.A.6 of the SPDES General Permit. The Applicant to revise
the statement in the SWPPP.
20. It does not appear that the inspection requirements of the SPDES General Permit are clearly
stated in the SWPPP. The Applicant shall revise the SWPPP to include the inspection
requirement as prescribed in Part IV.0 of the general permit.
21. It does not appear that the sample stormwater control facility maintenance agreement was
provided in the SWPPP; the Applicant to revise the SWPPP to include the maintenance
agreement.
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Town of Queensbury
Scoville Mini-Storage Facility
February 09,2017
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In the event the Planning Board or Town staff have any questions or require additional information,
please do not hesitate to contact me at (518) 824-1926.
Sincerely,
�� 141 7p�5-
'
Sean M. Doty, P.E., LEED AP, CMS4S
Principal
Manager, Municipal Engineering Services
cc: Sunny Sweet,Town Planning Office Administrator(via email)
Laura Moore,Town Land Use Planner(via e-mail)
File
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