What is a Stormwater Management Plan?

What is a Stormwater Management Plan?

It’s no secret that mankind has a significant impact on the environment, especially in construction. Reshaping the land affects local ecosystems and more. And even after a project has been completed, it will continue to clash with nature.  

One of the ways this occurs is through the flow of stormwater and melted ice or snow. Whatever water contacts, and the rate of contact, are two primary considerations during any construction project. And a stormwater management plan is an essential part of any project.

What is a Stormwater Management Plan (SWMP)? In simplest terms, it’s a plan that helps reduce pollution and contamination during construction projects by controlling runoff of rainwater or melted snow into streets, lawns, rivers, and other sites. 

We’re here to answer any questions you may have regarding that exact subject.

Why it’s Essential to Manage Stormwater?

Whenever we develop the land, we are disrupting nature. That’s not exactly a surprise, but one of the factors we cannot overlook is how disrupting the land affects stormwater flow.

The fact that the shape of the land disrupts the natural flow of water and its ability to soak into the ground is nothing to take lightly. Limiting and impeding these abilities can create various problems for the surrounding ecosystem and infrastructure, but it’s not the only issue.

Contamination of water runoff is just as, if not more, pressing as the flow. Regardless of whatever is in the way, water will find a way to continue its flow to a natural body of water. As it rolls over rooftops, sidewalks, and other imperviable surfaces, any harsh chemicals in these places will pollute the water.

If those chemicals reach local natural water bodies, they can harm and potentially kill any plant or wildlife within or even nearby. And because those water bodies may be a source of drinking water, nearby people are at high risk.

Even the smallest construction projects are bound to create some significant water runoff problems. These are a few examples of why every construction project is responsible for eliminating its impact on rainwater from beginning to completion and after that.

 Below you will find a list of the problems stormwater runoff can create:

  • Pollution: As water flows over the top of the surfaces in place, it will collect chemicals on top. Construction sites are the host of countless harmful substances that can cause severe damages if they enter a natural body of water. The ecosystems within will suffer, and it can even cause contamination of drinking water.
  • Erosion: As the water flows off impervious surfaces, it will find new paths. When water moves over land, it never has before. It can cause deterioration that may also be detrimental to ecosystems and the local community.  
  • Flooding: Without proper management in place, runoff stormwater will overflow drainage ditches, sewer systems, and storm drains. In any case, the excess flow of water is likely to lead to flooding.
  • Turbidity: If the water makes its way to the ground that can absorb it, it too may be in excess. When this occurs, it can cause turbidity or muddiness, ruining nearby land.
  • Infrastructure Damage: Flooding, erosion, pollution, and turbidity can wreak havoc on the local infrastructure. It’s not uncommon for a construction site without stormwater management plans in place to damage or even destroy it.

What’s the Difference between SWPPP and SWMP? 

Your involvement with construction projects likely has you dealing with a Storm Water Pollution Prevention Plan (SWPPP). However, you should not confuse an SWPPP with an SWMP, even if they relate to each other in many ways. 

The fundamental difference between the two is that an SWPPP is temporary while an SWMP is permanent. The SWPPP is intended to solve any potential issues regarding the flow and quality of stormwater during a project’s construction. Simultaneously, the SWMP is a permanent solution dealing with the matter once the project reaches completion. 

The plan you develop requires a few critical bits of information. The necessary details regarding the size, location, and primary point of contact include all the required details. Other than that, you also need to fill in the details of any streams or tributaries, lakes, water tables, and major rivers that the site is nearby and may impact. 

As with an SWPPP, the SWMP requires you to detail any methods by which you intend to manage the flow and quality of water runoff using minimum control measures and Best Management Practices, or BMP’s. After completion, the plan must be submitted and reviewed for approval to obtain a National Pollution Discharge Elimination System permit. 

Water Quality 

We might have mentioned pollution already, but it’s essential to keep in mind that these systems do more than ensure the excess water flow is under control. Even if the water is directed in the proper location, it likely isn’t clean. Remember, it’s carrying along with any debris or chemicals that it can collect along the way. Therefore protection of water quality is just as crucial to the process as any other.

Filtration of pollutants is critical to ensure drinking water and local ecosystem sources of drinking water are not contaminated.

How filtration is achieved is ultimately dependent on the system in use. MS4’s, for example, put filters into use throughout the system to prevent any chemicals or debris from following the water to its final destination. On the other hand, biofiltration swales use biological filters such as grass to perform the same task.  

What System Do I Need?

During the 1990s, the Environmental Protection Agency amended the Clean Water Act. Under this act, a national two-phase program is in effect to deal with water pollution caused by runoff stormwater.

Phase one of the program is in place to deal with stormwater discharges, while phase two regards smaller Municipal Separate Storm Sewer Systems (MS4s). In short, this act determines what systems you must put in place to deal with runoff. 

Exactly how you manage stormwater to satiate the Clean Water Act is dependent on a few factors. It’s tempting to believe that because there are already MS4’s in place, all you need to do is tap into them. 

However, these systems can only handle so much. An excess of water runoff can quickly lead to flooding or damage to the infrastructure, which is why there is a limit to how much water you can direct to them. That means you likely must come up with additional ways to manage stormwater. 

Below is a list of other forms of stormwater management systems you can include in your plan:

  • Bioretention Areas/Rain Gardens
  • Constructed Wetlands
  • Curb and Gutter Elimination
  • Drainage Ditches
  • Green Roofs
  • Permeable Pavements
  • Rain Barrels and Cisterns
  • Riparian Buffers
  • Sand and Organic Filters
  • Vegetated Filter Strips
  • Vegetated Swales/Dry Swales

But which of these solutions are acceptable for your project? How big do they have to be? There is room for creativity, meaning you can implement systems that complement your project’s layout or theme. 

However, the fact is that it depends on the project and your location—meaning it’s hard for us to provide you with any hard numbers. However, your local county or city will have different requirements than others, and you need to follow the guidelines they can provide you with.

Beyond Installation

It’s important to remember that the effectiveness of an SWMP goes beyond the implementation of water management systems. Upkeep is essential to their function and efficiency. Periodic maintenance is necessary to ensure they can continuously deal with water runoff.

It goes with saying that maintenance, like all other things, is specific to the system(s) you are using. Stormwater drains and drainage ditches, as an example, are subject to collecting debris as water flows to them. You must ensure you clear the waste and other deposits to prevent the system from clogging up and failing to perform its job.

Another example of maintenance is dealing with overgrowth in rain gardens, and biofiltration swales are essential to prevent similar debris will cause in other systems. No matter the method you use, regular inspections to ensure proper maintenance is in effect will likely occur.

These inspections can result in penalties and fines if you do not keep up with maintenance. However, that is usually a last-ditch effort to protect water flow and quality. The inspectors are likely to advise ways to improve maintenance long before taking other measures.

In the end, your stormwater management plan is a detailed document about your efforts to mitigate the impact of stormwater on a work site. It’s on you to implement the document’s systems and keep up with them. 

But you should view these systems as more than requirements to keep a project moving. Putting these efforts into effect is how we can reduce our impact on the environment, effectively protecting the local land, wildlife, and residents.

Have any further questions? Contact Path Light Pro to talk with a trusted consultant today.