Hydrodynamic Separators (HDS) – often referred to as oil-grit separators, swirl devices, or vortex separators – are best management practices often used to remove sediment, hydrocarbons, trash and debris from stormwater runoff.  HDS units are regularly used as either standalone treatment devices or pretreatment systems to detention, infiltration,

When it comes to using hydrodynamic separator (HDS) treatment devices, it is becoming commonplace to integrate them into storm sewer networks without worrying about the hydraulic impact of the device. After all, the majority of these devices are manholes or vaults with flow-through treatment, which are seemingly uncomplicated when compared to those

With stormwater pollutant removal requirements increasing nationwide, the demand for robust filtration has also increased.  Designing and specifying a properly functioning filter extends beyond specifying the correct product (media or membrane filter) and sizing correctly (flow or volume based).  These additional considerations are classified as

For this issue of the Stormwater Blog, I thought it would be beneficial to include a short video to better visually illustrate the durability and general advantages of Aluminized Type 2 (ALT2) corrugated steel pipe (CSP) detention/infiltration systems.The protective coating of aluminized type 2 corrugated steel pipes is composed of a free aluminum

One could argue that plants are the most essential part of biofiltration systems such as bioretention, high performance biofilters, and rain gardens.  However, plant design presents a unique challenge for system designers.  What types of plants should be selected?  Will they work well in the system? Will they be aesthetically pleasing?  Designing a

The International Stormwater Best Management Practices (BMP) Database project website (http://bmpdatabase.org) features a database that includes over 600 BMP performance studies.  This is a tremendous free resource for engineers, scientists, policymakers and others who seek to characterize the pollutant removal and hydrologic performance of various

In a previous post (Don’t Bypass Good Design Part 1: Offline Vs. Online Diversion Structures), I wrote about bypass structures and argued that they deserved more attention. In this follow-up, we’ll do just that by comparing two different ways to divert flow in a precast manhole. Option One: Using a manhole with different elevation outlet pipes With

Over the last 20 years of site-civil design, it has been interesting to see stormwater trends come and go.  Some design methodologies have disappeared, only to return later or in a nearby geography as the “new” approach.  Agency directives can shift based on new leadership or the prevalent regional concerns at the time.  As the construction

Months of design, pages of specifications, and tens or even hundreds of thousands of dollars may go into the design of a single bioswale, filtration basin, or other stormwater treatment system. So why do we spend so little time thinking about the flow control devices that make them work? This article is part one of a two-part series on bypass

Oh stormwater treatment performance lab testing, your time-consuming, methodical steps make me want to pull my hair out. You often leave me with more questions than answers. However, the benefits often counterbalance the challenges. Thank you for answering my questions, even if I must endure the tedious steps of the scientific method; a method that