Cost-benefit considerations for stormwater ponds

Costs for ponds typically include costs for embankment, riser and spillway structures, outfall protection, vegetative stabilization, excavation, and grading. Additional costs for site preparation can include soil amendments, precision grading, plant materials and creation of occluding layers in coarse-textured soil types if wetlands systems must be created on upland sites due to project constraints. Project costs can be lowered if existing pre-construction site conditions are carefully considered and isolated areas with hydric soils contained within the footprint of the project are utilized as stormwater management facilities.

Additional maintenance costs will be incurred until the establishment of the wetland ecosystem. Invasive plants must be culled and dead plants replaced. The outlet structure may have to be adjusted, based on seasonal observations, to achieve the proper water surface in the pond.

Construction and maintenance costs

The Introduction to stormwater BMPs section outlines a cost estimation method which site planners could use to compare the relative construction and maintenance costs for structural best management practices. These curves are excellent for purposes of comparison; however, it is recommended that construction and maintenance budgets should be based on site specific information. Utilizing the table below and the cost estimation worksheet for stormwater ponds, will allow designers to avoid over or under estimation of fixed costs. The table below lists the specific site components that are specific to stormwater ponds. Not included in this table are those cost items that are common to all construction projects, such as mobilization, traffic control, erosion and sediment control, permitting, etc.

This table shows Cost components for stormwater ponds
(Link to this table)

Implementation Stage	Primary Cost Components	Basic Cost Estimate	Other Considerations
Site Preparation	Tree & plant protection	Protection Cost ($/acre) x Affected Area (acre)	Removal of existing structures, topsoil removal and stockpiling
	Topsoil salvage	Salvage cost ($/acre) x Affected Area (acre)
	Clearing & grubbing	Clearing Cost ($/acre) x Affected Area (acre)
Site Formation	Excavation / grading	8-ft Depth Excavation Cost ($/acre) x Area (acre)	Soil & rock fill material, tunneling
	Hauling material offsite	Excavation Cost x (% of Material to be hauled away)
Structural Components	Inlet structure	($/structure)	Pipes, catchbasins, manholes, valves
	Outlet structure	($/structure)
Site Restoration	Seeding or sodding	Seeding Cost ($/acre) x Seeded Area (acre)	Tree protection, soil amendments, seed bed preparation, trails
	Planting / transplanting	Planting Cost ($/acre) x Planted Area (acre)
Annual Operation, Maintenance, and Inspection	Debris removal	Removal Cost ($/acre) x Area (acre) x Frequency (2 / 1yr)	Vegetation maintenance, cleaning of structures
	Sediment removal	Removal Cost ($/acre) x Area (acre) x Frequency (1 / 5yr)
	Gate / valve operation	Operation Cost ($) x Operation Frequency (2 / 1 yr)
	Inspection	Inspection Cost ($) x Inspection Frequency (2 / 1 yr)
	Mowing	Mowing Cost ($) x Mowing Frequency (4 / 1 yr)

Stormwater pond cost estimate worksheet
Link to this table

Project Title
Owner
Location
Project Number
Date
Description	Units	Quantity	Unit Cost	Total Estimated Price
Site Preparation
Tree removal - up to 12" diameter	each		$350.00	$0.00
Clear and grub brush	square yard		$1.50	$0.00
Tree protection - temp. fence	lineal foot		$3.00	$0.00
Topsoil - 6" depth, salvage on site	square yard		$4.50	$0.00
Site Formation
Excavation - 8' depth	square yard		$10.00	$0.00
Grading	square yard		$1.50	$0.00
Hauling off-site - 8' depth	square yard		$10.00	$0.00
Structural Components
Inlet structure	each		$2,000.00	$0.00
Overflow structure	each		$3,500.00	$0.00
Site Restoration
Sod - above vegetative bench	square yard		$4.50	$0.00
Soil preparation	square yard		$5.00	$0.00
Seeding - vegetative bench	square yard		$0.50	$0.00
Mulch	square yard		$2.00	$0.00
Subtotal				$0.00
10% Contingencies				$0.00
Subtotal				$0.00
Apply MN Location Factor				$0.00
TAL CONSTRUCTION COST				$0.00
Annual Operation and Maintenance
Debris removal	per visit		$100.00	$0.00
Remove invasive plants	per visit		$500.00	$0.00
Replant wetland vegetation	per plant		$10.00	$0.00
Repair erosion	square yard		$75.00	$0.00
Sediment removal and disposal	cubic yard		$10.00	$0.00
Mow	per visitt		$150.00	$0.00
Gate / valve operation	per visit		$125.00	$0.00
Inspection	per visit		$125.00	$0.00
Subtotal				$0.00
Apply MN Location Factor				$0.00
TOTAL ANNUAL O&M COST				$0.00
Minnesota Location Factors
Bemidji		0.963
Brainerd		1.003
Detroit Lakes		0.962
Duluth		0.991
Mankato		0.990
Bemidji		0.963
Minneapolis		1.035
Rochester		0.983
St. Paul		1.000
St. Cloud		1.002
Thief River Falls		1.042
Willmar		0.961
Windom		0.935

Note: Suggested unit costs are based on RS Means prices for Spring, 2005, then factored into an area basis based on typical design features for Constructed Wetlands BMPs. To be used for preliminary cost estimation

Related pages

• Overview for stormwater ponds
• Types of stormwater ponds
• Design criteria for stormwater ponds
• Design considerations for constructed stormwater ponds used for harvest and irrigation use/reuse
• Construction specifications for stormwater ponds
• Assessing the performance of stormwater ponds
• Operation and maintenance of stormwater ponds
• Cost-benefit considerations for stormwater ponds
• Calculating credits for stormwater ponds
• Stormwater wet pond fact sheet
• References for stormwater ponds
• Requirements, recommendations and information for using stormwater pond as a BMP in the MIDS calculator