Cost-benefit considerations for infiltration
The section on integrated stormwater management 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 cost estimation worksheet below will allow designers to avoid over or under estimation of fixed costs.
Infiltration trench and infiltration basin 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 | |
| Infiltration area protection - silt fence | lineal foot | $2.00 | $0.00 | |
| Topsoil - 6" depth, salvage on site | square yard | $4.50 | $0.00 | |
| Site Formation | ||||
| Excavation - 6' depth | square yard | $8.00 | $0.00 | |
| Grading | square yard | $1.50 | $0.00 | |
| Hauling off-site - 6' depth | square yard | $10.00 | $0.00 | |
| Structural Components | ||||
| Inlet structure | each | $1,500.00 | $0.00 | |
| Multi-stage outlet structure | each | $2,500.00 | $0.00 | |
| Site Restoration | ||||
| Sod filter strip | lineal foot | $1.50 | $0.00 | |
| Soil preparation | square yard | $5.00 | $0.00 | |
| Seeding - above outlet elevation | square yard | $0.50 | $0.00 | |
| Planting - below outlet elevation | square yard | $30.00 | $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 | ||||
| Replace planting media | square yard | $12.00 | $0.00 | |
| Debris removal | per visit | $50.00 | $0.00 | |
| Mow filter strips | per visit | $50.00 | $0.00 | |
| Sediment removal | per year | $500.00 | $0.00 | |
| Replace plants | per plant | $5.00 | $0.00 | |
| Erosion repair | square yard | $75.00 | $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 | $0.00 | |||
| Minnesota Location Factors | ||||
| Bemidji | 0.963 | |||
| Brainerd | 1.003 | |||
| Detroit Lakes | 0.962 | |||
| Duluth | 0.991 | |||
| Mankato | 0.990 | |||
| Bemidji | 0.963 | |||
| Minneapolis | 1.035 | |||
| Rochester | 0.983 | |||
| St. Paul | 1.000 | |||
| St. Cloud | 1.002 | |||
| Thief River Falls | 1.042 | |||
| Willmar | 0.961 | |||
| Windom | 0.935 | |||
Note: Suggested unit costs are based on RS Means prices for Spring, 2005, then factored into an area basis based on typical design features for Constructed Wetlands BMPs. To be used for preliminary cost estimation
The table below lists the specific site components that are specific to infiltration practices. Not included in this table are those cost items that are common to all construction projects, such as mobilization, traffic control, erosion and sediment control, permitting, etc.
Summary of infiltration practices cost components.
Link to this table
| Implementation Stage | Primary Cost Components | Basic Cost Estimate | Other Considerations |
|---|---|---|---|
| Site Preparation | Tree & plant protection | Protection Cost ($/acre) * Affected Area (acre) | Removal of existing structures, topsoil removal and stockpiling |
| Infiltration area protection | Silt fence cost ($/’foot) * Perimeter of infiltration area | ||
| Clearing & grubbing | Clearing Cost ($/acre) * Affected Area (acre) | ||
| Topsoil salvage | Salvage Cost ($/acre) * Affected Area | ||
| Site Formation | Excavation / grading | X-ft Depth Excavation Cost ($/acre) * Area (acre) | Soil & rock fill material, tunneling |
| Hauling material offsite | Excavation Cost * (% of Material to be hauled away) | ||
| Structural Components | Vault structure (for underground infiltration) | ($/structure) | Pipes, catchbasins, manholes, valves, vaults |
| Media (for infiltration trenches) | Media cost ($/cubic yard) * filter volume (cubic yard) | ||
| Geotextile | Geotextile cost ($/cy) * area of trench, including walls | ||
| inlet structure | ($/structure) | ||
| Overflow structure | ($/structure) | ||
| Observation well | ($/structure) | ||
| Site Restoration | Soil preparation | Topsoil or amendment cost ($/acre) * Area (acre) | Tree protection, soil amendments, seed bed preparation, trails |
| Seeding | Seeding Cost ($/acre) * Seeded Area (acre) | ||
| Filter strip | Sod cost ($/square foot) * filter strip area | ||
| Planting / transplanting | Planting Cost ($/acre) * Planted Area (acre) | ||
| Annual Operation, Maintenance, and Inspection | Sediment removal | Removal Cost ($/acre) * Area (acre) * Frequency (1 time per 5 years) | Vegetation maintenance, cleaning of structures |
| Debris removal | Removal Cost ($/acre) * Area (acre) * Frequency (2 time per year) | ||
| Inspection | Inspection Cost ($) * Inspection Frequency (6 times per year) | ||
| Mowing (for some vegetative filters) | Mowing Cost ($) * Mowing Frequency (6 times per year) |
Related pages
- Overview for infiltration
- Types of infiltration
- Design criteria for infiltration
- Construction specifications for infiltration
- Operation and maintenance of stormwater infiltration practices
- Assessing the performance of infiltration
- Calculating credits for infiltration
- Cost-benefit considerations for infiltration
- Case studies for infiltration
- External resources for infiltration
- References for infiltration
- Requirements, recommendations and information for using infiltration basin/underground infiltration BMPs in the MIDS calculator
- Understanding and interpreting soils and soil boring reports for infiltration BMPs
- Determining soil infiltration rates
- Cold climate considerations for infiltration practices - See [1], [2]