Stormwater pond/ wetland - construction inspection checklist.
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Site Status:
Construction Sequence Satisfactory/Unsatisfactory Comments
1. Pre-Construction/Materials and Equipment
Pre-construction meeting
Pipe and appurtenances on-site prior to construction and dimensions checked
1. Material (including protective coating, if specified)
2. Diameter
3. Dimensions of metal riser or pre-cast concrete outlet structure
4. Required dimensions between water control structures (orifices, weirs, etc.) are in accordance with approved plans
5. Barrel stub for prefabricated pipe structures at proper angle for design barrel slope
6. Number and dimensions of prefabricated antiseep collars
7. Watertight connectors and gaskets
8. Outlet drain valve
Project benchmark near pond site
Facility location staked out
Equipment for temporary de-watering
Temporary erosion and sediment control in place
2. Subgrade Preparation
Area beneath embankment stripped of all vegetation, topsoil, and organic matter
3. Pipe Installation
Method of installation detailed on plans
A. Bed preparation
Installation trench excavated with specified side slopes
Stable, uniform, dry subgrade of relatively impervious material (If subgrade is wet, contractor shall have defined steps before proceeding with installation)
Invert at proper elevation and grade
B. Pipe placement
Metal / plastic pipe
1. Watertight connectors and gaskets properly installed
2. Anti-seep collars properly spaced and having watertight connections to pipe
3. Backfill placed and tamped by hand under “haunches” of pipe
4. Remaining backfill placed in max. 8 inch lifts using small power tamping equipment until 2 feet cover over pipe is reached
Concrete pipe
1. Pipe set on blocks or concrete slab for pouring of low cradle
2. Pipe installed with rubber gasket joints with no spalling in gasket interface area
3. Excavation for lower half of anti-seep collar(s) with reinforcing steel set
4. Entire area where anti-seep collar(s) will come in contact with pipe coated with mastic or other approved waterproof sealant
5. Low cradle and bottom half of anti-seep collar installed as monolithic pour and of an approved mix
6. Upper half of anti-seep collar(s) formed with reinforcing steel set
7. Concrete for collar of an approved mix and vibrated into place (protected from freezing while curing, if necessary)
8. Forms stripped and collar inspected for honeycomb prior to backfilling. Parge if necessary.
C. Backfilling
Fill placed in maximum 8 inch lifts
Backfill taken minimum 2 feet above top of antiseep collar elevation before traversing with heavy equipment
4. Riser / Outlet Structure Installation
Riser located within embankment
A. Metal riser
Riser base excavated or formed on stable subgrade to design dimensions
Set on blocks to design elevations and plumbed
Reinforcing bars placed at right angles and projecting into sides of riser
Concrete poured so as to fill inside of riser to invert of barrel
B. Pre-cast concrete structurer
Dry and stable subgrade
Riser base set to design elevation
If more than one section, no spalling in gasket interface area; gasket or approved caulking material placed securely
Watertight and structurally sound collar or gasket joint where structure connects to pipe spillway
C. Poured concrete structure
Footing excavated or formed on stable subgrade, to design dimensions with reinforcing steel set
Structure formed to design dimensions, with reinforcing steel set as per plan
Concrete of an approved mix and vibrated into place (protected from freezing while curing, if necessary)
Forms stripped & inspected for honeycomb prior to backfilling; parge if necessary
5. Embankment Construction
Fill material
1. Fill placed in specified lifts and compacted with appropriate equipment
2. Constructed to design cross-section, side slopes and top width
3. Constructed to design elevation plus allowance for settlement
6. Impounded Area Construction
Excavated / graded to design contours and side slopes
Inlet pipes have adequate outfall protection
Forebay(s) constructed per plans
Pond benches construction per plans
7. Earth Emergency Spillway Construction
Spillway located in cut or structurally stabilized with riprap, gabions, concrete, etc.
Excavated to proper cross-section, side slopes and bottom width
Entrance channel, crest, and exit channel constructed to design grades and elevations
8. Outlet Protection
A. End section
Securely in place and properly backfilled
B. Endwall
Footing excavated or formed on stable subgrade, to design dimensions and reinforcing steel set, if specified
Endwall formed to design dimensions with reinforcing steel set as per plan
Concrete of an approved mix and vibrated into place (protected from freezing, if necessary)
Forms stripped and structure inspected for honeycomb prior to backfilling; parge if necessary
C. Riprap apron / channel
Apron / channel excavated to design cross-section with proper transition to existing ground
Filter fabric in place
Stone sized as per plan and uniformly place at the thickness specified
9. Vegetative Stabilization
Approved seed mixture or sod
Proper surface preparation and required soil mendments
Excelsior mat or other stabilization, as per plan
10. Miscellaneous
Drain for ponds having a permanent pool
Trash rack / anti-vortex device secured to outlet structure
Trash protection for low flow pipes, orifices, etc.
Fencing (when required)
Access road
Set aside for clean-out maintenance
11. Stormwater Wetlands
Adequate water balance
Variety of depth zones present
Approved pondscaping plan in place and budget for additional plantings
Plants and materials ordered 6 months prior to construction
Construction planned to allow for adequate planting and establishment of plant community (April-June planting window)
12. Final Inspection
Construction sediment removed from settling basin
Contributing drainage area stabilized
Vegetation established per specifications
Inlet and outlet structures operational
Actions to be Taken: