Please ensure Javascript is enabled for purposes of website accessibility

WQMP: Protecting Waterways from Urban Runoff


“Our primary objective when designing stormwater management systems is to ensure cost-effectiveness for our clients while simultaneously satisfying permit requirements,” said Hannah Lancaster, P.E., Project Manager at CDR. “We always focus on providing the most efficient and cost-effective solution possible. Our priority is to provide practical and affordable solutions that meet the specific needs of our clients.” 

Local creeks, rivers, and lakes can be negatively impacted by urban runoff containing harmful pollutants that degrade our water supplies and contaminate the habitat of many aquatic creatures. With new land development projects commencing every day; an increase in the concentration of new and pre-existing contaminants is to be expected, but there are also downstream ramifications like erosion, and to contend with. Hydromodification refers to human activities that alter natural water flow and quality, leading to ecological, economic, and social impacts. This may sound ominous, but there are ways to responsibly mitigate the impact of these urban improvements, which is why we have Water Quality Management Plans.  

What is WQMP?

WQMP stands for Water Quality Management Plan. If your project requires a grading permit from the city, there is a high chance that you will be required to provide a WQMP. These are special plans typically prepared during a project’s entitlement phase that need to be approved by the city before a project can move on to getting any necessary permits. These plans are used to ensure the health of local waterways and beaches through the prevention and abatement of stormwater runoff pollution.

The WQMP specifies Best Management Practices (BMPs) the property will be required to implement and maintain to guarantee clean stormwater compliance.

What is in a WQMP?

Basically, the information contained within a WQMP will describe the efforts being made to minimize the impact stormwater runoff will have on downstream bodies of water. In other words, information describing the efforts planned to mitigate any potential pollutants as they pertain to your local rivers, lakes, and oceans. These plans will examine every hydrological impact your land development project could generate that affects the surrounding area. As such, information compiled in this plan ranges from detailed site characteristics like project site slope and soil quality to listing structural and non-structural Best Management Practices (BMPs) and Low Impact Development (LID) features and how they will be incorporated.

We have another blog post that breaks down the different pieces involved in the submittal and approval process for WQMP in more detail, called “Streamlining the Stormwater Permitting & Application Process.

Woodland Hills Porsche 

The Woodland Hills Porsche project in LA County is an example of a project that required a unique approach to comply with the regional water quality board’s stormwater management plan. The site had a significant elevation difference from east to west, which made it difficult to incorporate traditional BMPs (like biofiltration basins) in the landscaping or planters. Additionally, the groundwater level was too shallow to allow for underground percolation or a dry well.

To overcome these challenges, the project team used a hybrid capture and re-use and biofiltration treatment system to satisfy stormwater requirements. The system included tiered planters along the perimeter of the site, with each tier sized and designed to overflow into the next. This created a cascading waterfall effect that not only treated stormwater but also provided an aesthetically pleasing feature for the site.

The project is under construction, and when complete, it will demonstrate the importance of considering the site’s specific characteristics when developing a WQMP and implementing effective stormwater management strategies despite limitations in space and infrastructure.

Best Management Practices (BMPs) 

BMPs refer to techniques or measures used to control land and activities to minimize contamination of nearby surface and groundwater. These methods may involve the use of structural and nonstructural equipment, along with maintenance procedures, and can be applied at any stage of development that has the potential to cause or produce pollution.

  •     Structural BMPs

Structural BMPs are designed to remove pollutants from stormwater runoff and/or reduce the volume of stormwater runoff.

  •     Non-Structural BMPs

Non-structural BMPs are focused on pollutant reduction, management of pollutants, and preservation of natural features.

Maserati of Anaheim Hills

The Maserati of Anaheim Hills project successfully met the requirements of water quality management using Filterra tree wells for biofiltration and solid CMP (corrugated metal pipe) for underground detention. The Filterra tree wells are four by four and five feet deep concrete tubs with a tree planted in special soil media layers. Project site runoff surface flows into the top of the system and percolates down through the layers, with some being used by the tree and the rest leaving through the bottom of the box and flowing into a solid CMP detention system with a small outlet and overflow weir for hydromodification flow control. Finally, the treated runoff and system overflow discharges to the public street. This project demonstrated an efficient and innovative approach to meeting water quality management requirements while still being cost-effective and meeting the needs of the client.

WQMP Commercial Development Resources Maserati Filtera Tree Well
WQMP Commercial Development Resources Maserati Filtera Tree Well Construction

Low Impact Development (LID)

Low Impact Development (LID) principles aim to replicate the natural hydrology of a site through techniques such as infiltration, filtering, storage, evaporation, and runoff detainment. This is done to maintain pre-development runoff rates and volumes. LID techniques are mandatory to comply with the regulations of the National Pollutant Discharge Elimination System (NPDES) set by the State’s Water Quality Control Board for commercial and industrial site plans. The compliance requirements are outlined in documents like the MS4 permit (PDF), WQMP Template (DOC), and Technical Guidance Document (PDF). To incorporate LID principles into a design, recommended methods include permeable pavements, vegetated filter strips, cisterns, rain barrels, grass swales and channels, bioretention or biofiltration facilities, and vegetated rooftops.

Popeyes Lemon Grove

The Popeyes restaurant in Lemon Grove is an example of a project that was designed to minimize the need for a full Stormwater Water Quality Management Plan (SWQMP); San Diego’s naming convention for a WQMP. The project site incorporated both permeable asphalt and concrete surfaces, allowing stormwater runoff to infiltrate into the ground and reducing the amount of runoff generated. As a result, a modified stormwater report was sufficient to meet the stormwater management requirements for the site. 

 In contrast, a newly constructed BMW dealership at a different site features basins and an underground detention system to control the flow of stormwater entering the public storm drain system. Both of these projects demonstrate different approaches to managing stormwater runoff and meeting the requirements of a WQMP.

When it comes to designing stormwater management systems that comply with Low Impact Development (LID) and Water Quality Management Plan (WQMP) requirements, the primary goal is to balance cost-effectiveness with meeting the needs of the permit and client. Innovative solutions that meet these requirements are always desirable, but cost considerations are paramount. These solutions can take many forms, such as the use of permeable asphalt and concrete surfaces to minimize runoff or the creation of tiered planters to capture and treat stormwater on-site. Ultimately, the goal is to meet the MS4 Permit requirements in the most cost-effective manner possible while still providing effective stormwater management for the site. In California, the MS4 permit stands for Municipal Separate Storm Sewer System permit, which is issued by the State Water Resources Control Board to regulate stormwater discharges from municipal stormwater systems in order to protect water quality in rivers, lakes, and other water bodies.

What is the difference between WQMP and SWPPP?

The management of stormwater runoff and erosion control are essential components of any construction or development project. Two common approaches to managing these issues are through the use of a WQMP and a Storm Water Pollution Prevention Plan (SWPPP).

A WQMP is a stormwater management plan that is designed to collect and treat stormwater post-construction permanently. It involves the use of Best Management Practices (BMPs) to treat water quality and sometimes to control water flow volume. Before implementation, these BMPs must be approved by the relevant authorities and undergo city plan checks. A SWPPP focuses on controlling erosion during construction only, whereas a WQMP is designed to manage stormwater runoff in perpetuity and must be maintained to ensure its continued effectiveness.

Overall, WQMPs and SWPPPs are important tools for managing stormwater runoff and erosion control during construction and development projects. By implementing effective BMPs and erosion control measures, developers can help to protect water quality and minimize the impact of their projects on nearby waterways.

CDR has an excellent history of achieving timely permit approvals. To learn more about CDR’s cost-effective design of stormwater management systems contact us to see how we can help you save time and money!