b.To construct concrete riser, cast the concrete in place or use pre-cast concrete elements. Use
lifting lugs to lift and transport pre-cast concrete risers. Do not use the top slab to lift the riser structure. Fill space between pipes and the pre-cast riser walls with non-shrink grout. The largest allowable dimension for the opening in the riser of connection of the outfall pipe is the outfall pipe diameter plus 4-inches.
c.To construct anti-seep collars, excavate the subgrade to the dimensions of the bottom half of
the collars. Use the excavation as the form for the bottom half of the anti-seep collars. Place formwork for the top half of the anti-seep collars.
d.Construct flow channel in accordance with Section 602.3.B.12 when applicable.
e.Construct principal spillway outfall pipe in accordance with Section 601 and the following:
i.Use Class A concrete in accordance with Section 1022. Place as shown in the Standard
Construction Details. Use concrete shims to establish grade and alignment of the pipe. Do not use lumber, masonry bricks, or any other non-concrete material for shims. ii. When placing the principal spillway outfall pipe partially or completely in fill, construct the fill embankment 24-inches above the proposed top of pipe. Excavate the trench once the fill is in place.
f.Maintain the outlet structure until project completion by removing accumulated sediment and
trash, stabilizing eroded areas, maintaining watertight joints, and as determined by the engineer. Dispose of sediment in accordance with Section 106.8.
C.Stormwater Management Pond
1.Before constructing the dam foundation and reservoir, clear and grub the area of trees, logs,
stumps, roots, brush, boulders, sod, topsoil, and rubbish. Grade all surfaces under the foundation to remove irregularities.
2.Construct the outlet structure in accordance with Section 910.3.B and as noted in the Contract.
3.Excavation
a.For a wet or dry stormwater management pond, excavate to the lines and grades shown in the
contract.
b.Excavate for an infiltration basin to within 2-feet of the designed bottom elevation, while
maintaining the slope required as shown on the plans. Do not allow construction equipment to travel within 2-feet of the designed bottom of an infiltration basin. Do not stockpile within the bottom footprint area of the infiltration basin. Install silt fence of compost filter logs between stockpiles and the top of bank.
c.Obtain the concurrence of the stormwater engineer before removing the last 2-feet of
material to the bottom of an infiltration basin. Remove the material by working from the middle of the facility to the outside edges or from 1 side to the other. Limit the amount of ingress and egress points to as few as possible. Upon removal of the last 2-feet of material, scarify the bottom elevation. Immediately stabilize ingress and egress points when no longer needed in accordance with Section 908.
4.Construct the foundation, embankment, and slope in accordance with Section 202, except for
the infiltration basin bottom elevation. If the engineer allows, deposit the materials unsuitable for use in the dam foundation and embankment on slopes. Otherwise, use excess material meeting the requirements for embankment to construct other embankments on the contract. Remove excess and unsuitable material. Excavate rock in accordance with Section 202.
a.Key the foundation cut-off trench into original ground in accordance with the contract.
Excavate the foundation cutoff trench to a minimum bottom width of 4-feet before placing the dam embankment. Construct side slopes for the cut-off trench no steeper than 1 to 1.
b.Construct the pond liner in accordance with Section 202 and to the lines and grades shown in
the contract.
5.Dewater in accordance with Sections 902 and 906.
6.Stabilize in accordance with Section 908, and in accordance with the Contract.
7.Maintain the stormwater management pond until final project acceptance. Maintenance
includes:
a.Annual mowing of side slopes;
b.removing accumulated sediment and trash;
c.stabilizing eroded areas in accordance with Section 908;
d.removing noxious or invasive plant species listed by the Delaware Department of Agriculture;
and
e.disposing of sediment in accordance with Section 106.8.
D.Construct the infiltration trenches to the dimensions shown in the contract after concurrence
from the stormwater engineer. Do not allow construction equipment to travel within 2-feet of the infiltration trench bottom area. Do not stockpile within 10-feet of the infiltration trench area. Install silt fence or compost filter log between stockpiles and the infiltration trench.
1.Subgrade establishment
a.Excavate to the design subgrade elevation. Do not allow construction equipment to run within
2-feet of the designed bottom elevation.
b.Prepare the foundation in accordance with the contract.
c.After completing the excavation, line the sides of the stone reservoir with geotextile. Place the
geotextile with a 12-inch minimum overlap on the trench sides. Provide enough geotextile to completely cover the stone surface with a minimum of 2-feet overlap. Secure in place using excess infiltration stone or other methods approved by the engineer. Remove excess geotextile covering the stone surface after a satisfactory stand of permanent vegetation establishes itself, as determined by the engineer, and with concurrence of the stormwater engineer.
2.Aggregate placement
a.Construct an inspection port consisting of a 6-inch diameter schedule 40 PVC pipe with 4 rows
of 3/8-inch diameter holes evenly spaced around the pipe and 6-inches on center vertically. Place a removable cap on the top and place an 18-inch length of rebar through the pipe from side to side and secure on the bottom to serve as an anchoring system. Extend the inspection port from the bottom of the trench to 1-foot above the top stone elevation.
b.Place No. 3 infiltration stone in accordance with the contract.
c.Place HDPE pipe in accordance with the contract, making sure to have solid non-perforated
caps on both ends.
3.Maintain the infiltration trench until final project acceptance. Maintenance includes:
a.Annual mowing of side slopes;
b.removing accumulated sediment and trash;
c.stabilizing eroded areas in accordance with Section 908;
d.removing noxious or invasive plant species listed by the Delaware Department of Agriculture;
and
e.disposing of sediment in accordance with Section 106.8.
E.Construct bioretention areas to the dimensions shown in the contract. Do not allow construction
equipment to travel within 2-feet of the designed bottom of the bioretention area. Do not stockpile on or within 10-feet of the bioretention area. Install silt fence or compost filter log between stockpiles and the infiltration trench.
1.Construct outlet structures in accordance with Section 910.3.B and in accordance with the
contract.
2.Excavate to the design subgrade elevation and scarify. Do not allow construction equipment to
travel within 2-feet of the designed bottom elevation.
3.Prepare the foundation in accordance with the contract.
4.Bioretention Area Components Placement.
a.Place the inspection port using 6-inch diameter schedule 40 PVC pipe with 4 rows of 3/8-inch
diameter holes, evenly spaced around the pipe and 6-inches on center vertically. Wrap perforated pipe with a metal screen with openings no bigger than 1/2-inch and no smaller than 3/8-inch. Place a removable cap on the top and place an 18-inch length of rebar through the pipe from side to side and secure on the bottom to serve as an anchoring system. Extend the inspection port from the bottom of the trench to 1-foot above the top biosoil mix elevation.
b.Place No. 8 infiltration stone in accordance with the contract.
c.Place underdrain using 6-inch diameter schedule 40 PVC with 4 rows of 3/8-inch diameter
holes, evenly spaced around the pipe and 6-inches on center vertically in accordance with the contract. Wrap perforated pipe with a metal screen with openings no bigger than 1/2-inch and no smaller than 3/8-inch. There are no perforations in the cleanout pipe.
d.Place biosoil mix in accordance with the contract.
e.Place a minimum of 4-inches of triple shredded mulch over the entire surface of the biosoil
mix.
5.Dewater in accordance with Sections 902 and 906.
6.Stabilize in accordance with Section 908 and the contract
7.Maintain the bioretention area until final project acceptance. Maintenance includes:
a.Annual mowing of side slopes.
b.Removing accumulated sediment and trash.
c.Stabilizing eroded areas in accordance with Section 908.
d.Removing noxious or invasive plant species listed by the Delaware Department of Agriculture.
e.Disposing of sediment in accordance with Section 106.8.
F.Construct bioswale to the dimensions shown on the contract after concurrence from the
stormwater engineer. Do not allow construction equipment to travel within 2-feet of the channel bottom areas. Do not stockpile within 10-feet of the bioswale area.
1.Subgrade establishment
a.Excavate to the design subgrade elevation. Do not allow construction equipment to run within
2-feet of the designed bottom elevation.
b.Prepare the foundation in accordance with the contract.
c.After completing the spreader excavation, line the sides of the stone reservoir with geotextile.
Place the geotextile with a 12-inch minimum overlap on the trench sides. Provide enough geotextile to completely cover the stone surface with a minimum of 2-feet overlap. Secure in place using excess infiltration stone or other methods approved by the engineer. Remove excess geotextile covering the stone surface after a satisfactory stand of permanent
vegetation establishes itself, as determined by the engineer, and with concurrence of the Stormwater Engineer.
d.After completing swale excavation apply soil amendments and install plantings.
2.Stone Check Dam
a.Install stone check dam as shown on the plans and in accordance with Section 907.
3.Maintain the bioswale until final project acceptance. Maintenance includes:
a.Annual mowing of side slopes;
b.removing accumulated sediment and trash;
c.stabilizing eroded areas in accordance with Section 908;
d.removing noxious or invasive plant species listed by the Delaware Department of Agriculture;
e.disposing of sediment in accordance with Section 106.8.
G.Submit to the engineer all required post construction verification documentation required for
BMP approval, in accordance with DNREC regulations. All stormwater BMPs must be approved by the Department prior to Final Acceptance.
910.4Method of Measurement.
A.The Department will measure the quantity of:
1.Infiltration stone by the cubic yard of stone.
2.Clay borrow by the cubic yard measured in accordance with Section 209.4.
3.Concrete outlet structure by each or lump sum.
4.Stormwater management pond as the number of cubic yards of material used to construct the
A.The Department will pay the quantity of infiltration stone at the contract unit price per cubic yard.
Price and payment will constitute full compensation for subgrade preparation and providing and placing all materials.
B.The Department will pay the quantity of clay borrow at the contract unit price per cubic yard.
Price and payment will constitute full compensation for stripping, excavating, hauling, placing, and compacting borrow material.
C.The Department will pay the quantity of concrete outlet structures at the contract unit price per
each or lump sum. Price and payment will constitute full compensation for excavating, dewatering, ground preparation, providing and placing all materials, placing and curing PCC, and welding.
D.The Department will pay the quantity of stormwater management ponds at the contract unit price
per cubic yard. Price and payment will constitute full compensation for:
1.Clearing and grubbing;
2.disposing of obstructions;
3.excavating;
4.placing embankment;
5.grading;
6.compacting;
7.removing and disposing of unsuitable material;
8.salvaging and stockpiling soil for re-use; and
9.dewatering.
E.The Department will pay the quantity of infiltration trench at the contract unit price per cubic
yard. Price and payment will constitute full compensation for:
1.Excavating;
2.foundation preparation; and
3.providing and placing all materials including geotextile fabric not paid for with infiltration stone.
4.The Department will pay for infiltration stone in accordance with Item 910001.
F.The Department will pay the quantity of bioretention area at the contract unit price per cubic
yard. Price and payment will constitute full compensation for:
1.Excavating;
2.foundation preparation;
3.providing and placing all materials; and
4.dewatering.
5.The Department will pay for:
a.Infiltration stone with Item 910002.
b.Biosoil mix with Item 910011.
G.The Department will pay for biosoil mix at the contract unit price per cubic yard. Price and
payment will constitute full compensation for preparing the subgrade and providing and placing material.
H.The Department will pay for bioswale at the contract unit price per cubic yard. Price and payment
Delaware revises spec sections through supplementals and new editions. We check this one every week and email you the day it changes. Free, no account.
Source: Delaware Standard Specifications for Road and Bridge Construction, 2026 Edition. Pages 624–0 of 786. View official source ↗
Scoped to Delaware Standard Specifications for Road & Bridge Construction, Section 910 — STORMWATER MANAGEMENT FACILITIES. Every answer cites the section it came from, with a verification date — don’t trust a percentage, click the citation.