Construction sites are one of the largest polluters of natural waterways in the United States. According to the EPA, construction sites emit sediment runoff at a 10x to 20x greater rate than farm land and 1000x more than forests. Left unchecked, these impacts can damage nearby waterways, violate federal and state regulations, and result in costly fines.
Stormwater Best Management Practices (BMPs) are methods, structures, or controls designed to prevent or reduce pollution from construction activities. Implementing the right BMPs is essential for maintaining compliance under programs like the National Pollutant Discharge Elimination System (NPDES) and ensuring sustainable project outcomes.
This step-by-step guide explains how to select and implement BMPs effectively, helping contractors and developers minimize environmental impact while protecting their project’s schedule and budget.
Examples of Common Stormwater BMPs
BMPs vary depending on site conditions and regulatory requirements. Common examples include:
- Erosion Control: Erosion blankets, temporary seeding, and mulch to stabilize bare soil.
- Sediment Control: Silt fences, sediment traps, filter socks, and sediment basins that capture soil before it leaves the site.
- Runoff Management: Vegetated swales, biofiltration strips, and temporary detention ponds that slow water flow and filter pollutants.
- Non-Structural Practices: Proper material storage, spill prevention measures, and worker training to reduce contamination risk.
Each BMP is tethered to address specific risks. Often, a combination of multiple BMPs is needed for effective stormwater management.
How to Select the Right BMPs for an Active Construction Site
Understanding what common BMPs are available and what problems they address is important to selecting the right stormwater controls. However, controls should be used strategically to make the best use of the local environment and construction site. Here is a step-by-step guide to selecting the right BMPs for your next project.
Step 1: Conduct a Site Assessment
The first step in choosing BMPs is a comprehensive site assessment. Evaluate topography, soil types, drainage patterns, vegetation, and nearby water bodies. Identify areas prone to erosion, sediment displacement, or stormwater concentration.
Understanding your site’s unique conditions allows you to match BMPs to specific risks. For example, steep slopes may require temporary erosion blankets, while flat areas near streams may benefit more from sediment traps or vegetative buffers.
Step 2: Understand Regulatory Requirements
Before selecting BMPs, review federal, state, and local stormwater regulations. Construction projects that disturb more than one acre of soil typically require NPDES permit coverage, including a Stormwater Pollution Prevention Plan (SWPPP).
Regulatory agencies may specify minimum BMPs for sediment control, runoff management, and post-construction stabilization. Compliance is not optional—failure to meet these standards can result in fines, work stoppages, or liability for downstream water pollution.
Step 3: Identify Primary Construction Site Risks
Each construction site presents different environmental challenges, from previously eroded soil to poor drainage. Some common site risks you may encounter include:
- Soil erosion and sediment transport from grading or excavation.
- Stormwater contamination from construction materials, fuels, or chemicals.
- Runoff from impervious surfaces, such as parking lots or paved access roads.
- Disturbance to riparian zones or wetlands, which can increase downstream flooding and sediment loads.
Documenting these risks helps prioritize BMP selection and ensures the most effective controls are implemented.
Step 4: Match BMPs to Site Conditions
BMPs fall into three main categories: erosion controls, sediment controls, and runoff management. Each addresses a specific type of risk.
- Erosion controls prevent soil from leaving the site. Examples include temporary vegetation, erosion blankets, silt fences, and hydroseeding. They’re particularly important on slopes and areas exposed during grading.
- Sediment controls capture soil particles that have already detached, preventing them from reaching waterways. Sediment basins, traps, and filter socks are commonly used in construction and excavation areas.
- Runoff management BMPs regulate the quantity and flow rate of stormwater. Detention basins, swales, and vegetative buffers help slow water, promote infiltration, and filter pollutants.
Selecting the right BMP requires matching the control to the site’s specific erosion, sediment, and runoff risks.
Step 5: Prioritize BMPs by Effectiveness and Feasibility
Once potential BMPs are identified, they should be evaluated for effectiveness, cost, and practicality. The goal is to determine how well each option reduces sediment, erosion, or pollutants while fitting within project timelines and budgets.
It’s also important to assess whether a BMP can be installed quickly, endure severe weather, and be maintained easily throughout the project. For instance, a sediment basin may be highly effective for large construction sites but requires more space and labor than a simple silt fence.
Step 6: Integrate Temporary and Permanent Controls
Construction sites require both temporary and permanent BMPs. Temporary measures are used during active construction to control sediment and runoff, while permanent BMPs remain after project completion to ensure ongoing stormwater management.
Temporary controls might include:
- Silt fences along slopes or property boundaries
- Erosion control blankets over bare soil
- Sediment traps in drainage channels
Permanent controls could involve:
- Vegetative buffers around streams
- Stabilized swales and detention ponds
- Landscaping with deep-rooted plants for long-term soil stabilization
Combining temporary and permanent BMPs ensures both short-term compliance and long-term environmental protection.
Step 7: Develop a Maintenance Plan
Site maintenance and inspections are an integral part of any SWPPP. Sites should be inspected every seven days or after storms to remove sediment buildup, clean inlet filters, repair damage, restore crops, and ensure proper function.
Documenting inspections and maintenance is often required for NPDES compliance.
Step 8: Train Staff and Contractors
Even the best BMPs fail without proper installation and adherence. Train on-site staff and subcontractors on proper BMP installation and maintenance procedures to ensure that they can identify risks or problems before they occur.
Step 9: Document Everything
Maintaining thorough records is a core component of regulatory compliance. Document all BMP selections, installations, inspections, and maintenance actions.
Proper documentation not only demonstrates compliance during audits but also provides a reference for future projects, helping contractors refine BMP selection and implementation strategies.
Stormwater erosion controls are only as effective as you make them, so choosing the right BMPs and maintaining them after installation is key to ensuring proper regulatory compliance.
FAQs
What are BMPs in construction?
BMPs, or Best Management Practices, are techniques, structures, or methods used to reduce pollution and control stormwater on construction sites. Common BMPs include silt fences, ripraps, erosion control blankets, and sediment basins.
Do all construction sites require BMPs?
Most sites disturbing one acre or more require BMPs under NPDES permit regulations, though smaller sites may also benefit from BMPs to prevent erosion and sediment loss.
How often should BMPs be inspected?
BMPs should be inspected after major rainfall events and at least once a week during active construction, with documentation maintained for compliance.
What is the difference between temporary and permanent BMPs?
Temporary BMPs control sediment and runoff during construction, while permanent BMPs provide long-term stormwater management after project completion.