Stormwater Report_Cover "Stormwater Management Report"
For a New Equipment Storage Building to serve
`A-1 Treeworks'
Located at
NT?'! 15 2013
308 Corinth Road
Queensbury, New York
November 2013
Introduction
The proposed `A-1 Treeworks' equipment storage building is to be constructed at 308 Corinth
Road, on a site that currently has a residence and detached garage. The project area for the new
building is located behind (north) the detached garage, and that area consists of a mix of grass,
woodland, and dirt travel paths. This project involves construction of a storage building to protect
equipment owned by A-1 Tree works. A gravel driving surface will be used to access the storage
building and an open area will be created to temporarily store wood chips. An existing buffer along
the access driveway will be enhanced with young trees removed from the development area. The
project area is approximately 0.99 acres of the total 3.49 acre parcel. Overall relief of the project
area is approximately 10', and soil on the site consists of uniform deep sand, consistent with an"A"
soil series. This information was confirmed by subsurface investigations performed by Jarrett
Engineers.
A supporting stormwater system to manage runoff from the building and driving surface has been
developed. The stormwater management system is to consist of pre-treatment trench in the driving
areas followed by infiltration basin. The stormwater management system for this project is intended
to be in compliance with the:
• Town of Queensbury Stormwater Management Standards as defined in Chaper 147 of the
Zoning Code, which reference to the technical guidelines included in the NYSDEC
Stormwater Management Design Manual(August 2010)
Runoff Calculations
Stormwater conditions represented in this report are based on modeling of the site for both the "pre-
development", or existing, and"post-development"or predicted future conditions. Stormwater peak
flows, both rate and volume, are calculated for the 50 year rain event using"Hydrocad" Stormwater
software which is based on TR-20 methodology.
A-1 Treeworks November 2013 .
"Stormwater Control Report"
Stormwater models should be thought of as reasonable comparisons of `before' and `after'
development, under the conditions modeled, and not a predictor of actual runoff rates under all
conditions. Actual runoff rates can vary from predicted flow rates due to conditions such as rainfall
patterns, soil type, vegetation patterns, and soil moisture conditions, etc. which can be highly
variable over time and geographic area.
Pre-development (Existing) Stormwater Conditions
Site runoff has been modeled with drainage "subcatchments", or sub-watersheds. The pre-
development stormwater rate for the subcatchments has been calculated at the rates and volumes
shown in the stormwater comparison table.
Post-Development Stormwater Conditions (No Mitivation)
The constructions of the proposed buildings have been modeled using "subcatchments", or sub-
watersheds. Calculations show that the stormwater runoff volume and rate will increase without
proper mitigation(see stormwater comparison table).
Recommended Stormwater Runoff Management (Mitigation)
The above sections show that stormwater runoff volume and rate leaving the site will increase after
development unless provisions are taken to manage stormwater on the site. To reduce stormwater
runoff rates to conform to Queensbury stormwater standards and to minimize stormwater impacts,
stormwater devices are proposed to capture,treat, and infiltrate the stormwater from the impervious
areas.
The attached calculations show that with the stormwater mitigation in place, predicted stormwater
runoff leaving the site will be below the existing runoff values.
SITE SUMMARY TABLE
EVENT PRE-CONS POST-CONS STATUS
50 YR (VOL) (af) 0.02 0.01 PASS
TE)
Post development calculations are below the pre-development rates for the 50 year storm event
with all mitigation measures installed.
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. A-1 Treeworks November 2013
"Stormwater Control Report"
Temporary Erosion & Sediment Controls during Construction
The site will be most susceptible to erosion and sediment problems during the construction phase of
the project. This can result in sedimentation in the downstream drainage swale and permanent
stormwater control devices. To prevent erosion during the construction phase, temporary erosion
control measures will be used. Sediment barriers/prevention erected/constructed prevents sediment
from traveling off site. [Construction details for temporary and permanent stormwater and erosion
control devices are appended to this report.] All disturbed areas will be seeded as dictated below
and dust will be controlled on roadways using water,or other approved methods.
Site Stabilization
The operator shall initiate stabilization measures as soon as practicable in portions of the site where
construction activities have temporarily or permanently ceased, but in no case more than 7 days
after the construction activity in that portion of the site has temporarily or permanently ceased.
This requirement does not apply to the following:
Where the initiation of stabilization measures by the 7th day after construction activity temporarily
or permanently ceased is precluded by unforeseen snow cover or frozen ground conditions,
stabilization measures shall be initiated as soon as practicable.
Where construction activity on a portion of the site has temporarily ceased, and earth-disturbing
activities will be resumed within twenty-one days, temporary stabilization measures need not be
initiated on that portion of the site as long as erosion and sediment control practices have
demonstrated their ability to prevent environmental degradation.
Maintenance
During construction, sediment shall be removed from sediment control devices whenever their
capacity has been reduced by fifty (50)percent from the design capacity.
All permanent stormwater control devices shall have any silt removed from them, and generally
updated to their full function prior to ceasing construction activities on the site. Once construction
has been completed on the site, the operator shall inspect the basins on a routine basis. If the
inspection determines that the functional volume/capacity has been lost due to siltation, damage,
etc. the device(s) shall be cleaned and/or repaired to their intended function.
Construction Phasing & Sequencing
Phasing is not currently planned. (Planning for future development is shown on site plans).
Construction is assumed to begin in Fall/winter 2013±. See Drawings for Construction Sequence
Schedule.
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A-1 Treeworks November 2013
"Stormwater Control Report"
Pollution Prevention/Waste Storage,
Construction chemicals will be stored in construction trailers or other secured sheds/cabinets, or
off-site away from stormwater runoff. All litter and construction debris outside of building(s) will
be cleaned up after each day's work.
Inspection Requirements
The applicant shall have a designated representative monitor construction and inspect all erosion
and sediment control practices as well as stormwater management devices for 1) effectiveness, and
2) compliance with the approved site plan. Inspection frequency and documentation requirements
shall be in accordance with Town of Queensbury requirements.
Maintenance Agreement Requirements
The Town shall approve a formal maintenance agreement for stormwater management facilities
binding on all current and subsequent landowners and recorded in the office of the County Clerk as
a deed restriction on the property prior to final plan approval.
SWPPP Prepared by:
JARRE'IT Engineers, PLLC
P,c,oV New
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H. Thomas Jarrett, P.E.
Principal
Appendices:
1. Stormwater Comparison chart
2. WQv&Pretreatment
3. Pre-Construction Conditions(PRE)
4. Post-Construction Conditions (POST) (with mitigation)
5. Pre &Post-Construction Hydrocad Calculations (50 yr storm events)
6. Stormwater Report(sample)
7. Stormwater Maintenance Agreement
8. NRCS Soil Resource Report for Warren County,New York
9. Jarrett Engineers Site Plans
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