HomeMy WebLinkAboutCocoran Apmnts Storm Drain 18 Aug 2023 (2)THE DYER GROUP, LLC • 343 E 4th NORTH, SUITE 108 • REXBURG, ID 83440 - 6001
208.390.9700 (VOICE AND TEXT) • wdyer@thedyergroup.com
COCORAN APARTMENTS
STORM DRAIN SYSTEM
Plans
Specifications
Design Calculations
August 2023
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COCORAN APARTMENTS DRAINAGE
SPECIAL PROVISIONS
STORM DRAINAGE
General: It is required to construct storm drain facilities to serve the parking lot and front half of
the new apartment complex building to be constructed. This work includes installation of two
catch basins (one for filtering), connecting storm drain piping, and a storm water infiltration
system as detailed on the Drawings.
Standard Specifications to be used for this project are the Idaho Standards for Public Works
Construction (ISPWC), 2020 edition, as supplemented by the specification information that
follows.
Materials: use the following materials for the storm drainage systems:
• ASTM C-478 precast reinforced concrete structures for Type B catch basins, 30” interior
diameter x 4’ deep as detailed on the Drawings; Precision Precast, or approved equal
• Heavy-duty cast-iron rings and slotted inlet grates on catch basins; East Jordan Foundry
1610, or approved equal
• ASTM D-3034 SDR 26 PVC pipe and fittings for storm drain, including gasketed downturned
90° bend inside filtering catch basin going to the infiltrators; JM Eagle, or approved equal
• PVC glue, washed sand, and non-shrink grout for PVC piping connections to Type B catch
basins
• Nonwoven polypropylene geotextile drainage fabric for enveloping washed rock around and
under infiltrators; Mirafi 160N, Winfab 600N, or approved equal
• 2” minus washed drain rock or crushed stone for infiltrator bed and stone envelope
• Polyethylene subsurface storm water management chamber structures (infiltrators); ADS
StormTech SC-740, or approved equal
Workmanship: Follow the general layout of the storm drainage system as depicted on the
architectural site plan, or modify it as required/desired after discussion with the Engineer.
Determine the necessary grade elevation elevations for the catch basin inlet grates so the
parking lot area can be appropriately sloped to them.
Catch Basins – Furnish and install the catch basin structures in accordance with the Standard
Specifications to the required elevations as determined by the elevations and needed grade in
the parking lot.
Excavate to the required catch basin locations and elevations, compact the subgrade, provide a
layer of washed or crushed gravel under the bottom of the catch basin to facilitate positioning and
leveling, and install the precast catch basin structures.
For the filtering catch basin prior to water entering storm water entering the infiltrators, determine
the elevation for the storm drain piping to leave the structure and properly connect to the storm
drain infiltrator, and then carefully knock out the concrete wall of the precast catch basin structure
to accommodate the piping connection.
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Insert the storm drain pipe into in this filtering catch basin a sufficient distance to be able to install
the downturned 90° bend catch basin as shown on the Drawings so the catch basin can serve as
a storm drain pretreatment structure to separate solids and oils from the water before it enters the
infiltration chamber. The 90° bend is to be a gasketed push-on fitting so it can be removed for
hydraulic cleaning of the storm drain pipeline and infiltration gallery as needed in the future.
To assure a watertight connection and appropriate bond between the PVC piping and the catch
basin concrete, it is necessary to treat the area on the pipe that will be grouted in the wall of the
catch basin. Apply PVC primer and cement on the exterior of the PVC pipe that will be in the
grouted connection area. Then sprinkle clean silica sand on the PVC cement, making sure to
cover the entire perimeter, and allow the application to cure for a minimum of 15 minutes before
placing the pipe in the wall of the structure and then applying the non-shrink grout. This will
ensure a secure and watertight bond between the PVC pipe and the concrete grout.
Furnish and place the required inlet grates and ring frames on the catch basins, assuring the mud
ring on the frame is properly fitted interior to the diameter of the catch basin to hold the assembly
in place and provide sliding resistance.
Place non-shrink concrete grout to fill any remaining holes or voids in the catch basin structure
installations. Thoroughly clean and remove all debris from the floor of the catch basins upon
completion of construction.
Storm Drain Piping – Install the storm drain piping between the catch basins and infiltrators in
accordance with the Standard Specifications and as shown on the Site Plan. Connect the piping
to the storm water management chamber (infiltrator) structure in accordance with the
manufacturer’s recommendations.
Backfill and compact the pipe trenches and around the catch basins to 96% of maximum density,
making special effort to install and thoroughly compact material under the piping connection to
the catch basins.
Storm Drain Infiltrators – Excavate for the washed rock infiltration bed for the storm drain infiltrator
structure to the required dimensions and level grade, scarify the subgrade to enhance infiltration
(do not compact!), place the geotextile drainage fabric, and install the washed rock bed.
Then install the storm water management chamber structure (infiltrator) on the initial washed rock
bed and connect the storm drain pipe in accordance with the manufacturer’s recommendations.
After the storm drain infiltrator structure is installed and properly positioned, place additional
washed rock inside of the separator fabric against the trench walls and around the sides and top
of the chamber to the dimensions and height indicated on the Drawings, capping the washed rock
installation with the drainage fabric.
Place pit run and crushed 3/4" gravel backfill above the fabric to the parking lot subgrade
surface elevation and compact in a manner to avoid damage to the underlying infiltrator
structure. Grade the completed subgrade to match the required parking lot grade and
elevations.
-- End of Special Provisions --