Calculating credits for stormwater ponds Revision as of 21:54, 15 February 2013 by PLeegar (talk | contribs) (→Construction and maintenance costs)
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 in Appendix D, 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) |