The Stormwater Blog 

Contech Stormwater experts discussing Low Impact Development, Onsite Water Management, Rainwater Harvesting and all things Stormwater.


Regulations


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Manufactured Stormwater Treatment Devices (MTDs) Frustrations, Misperceptions, and Concerns.  Part 2: Crossing the MTD Divide

The initial wave of manufactured treatment devices (MTDs) were generally simpler than options available today.  With few exceptions, early MTDs were comprised predominantly of swirl/vortex and other types of gravity separators that targeted solids and floating pollutants.  State and local stormwater programs were in their infancy and were predominantly focused on reducing suspended solids loads.  Our knowledge of particle size distributions and other common pollutants carried by stormwater paled in comparison to what we know today.  MTD testing protocols were non-existent leaving early MTD providers to devise their own and make their case for acceptance.  Regulators recognizing the need for underground solutions, especially in urban areas, implemented crude MTD performance criteria typically rooted in demonstrating removal of coarse solids in the laboratory.

Manufactured Stormwater Treatment Devices (MTDs) Frustrations, Misperceptions, and Concerns.  Part 1: Frustration is a Two-Way Street
Having spent the last sixteen years immersed in the world of stormwater best management practices (BMPs), with particular emphasis on manufactured treatment devices (MTDs), I’ve repeatedly borne witness to the frustrations, misperceptions, and concerns raised by all walks of stormwater professionals relative to MTDs.  
Categories: Regulations
Limited Parking
This month’s blog post comes from Janice Kaspersen, editor of Stormwater magazine.

Did you drive to work this morning? Was a parking space waiting for you when you arrived? Many cities require developers to provide a minimum number of parking spaces for office, retail, and residential buildings; sometimes the number is based on the square footage of the building, sometimes on occupancy. Many calculate the required number of spaces based on peak demand. 

Categories: Regulations
How to Size a Hydrodynamic Separator
Hydrodynamic Separators (HDS) have been used in the stormwater industry for over 20 years.  They are effective at removing TSS, hydrocarbons, and trash and debris from stormwater runoff and are often used for standalone treatment or pretreatment to filtration, detention, infiltration and rainwater harvesting system.  With the varied applications for HDS units comes a multitude of sizing options. 
All Stormwater Particles Are Not The Same Part 2: Particle Shape And Density

EPA selected a removal standard of 80% total suspended solids (TSS) removal as the target pollutant of concern due to high TSS concentrations ubiquitous impact on water quality and degradation to aquatic habitat. Many other pollutants of concern are particle-bound, and TSS is thereby a surrogate for other pollutants. Testing methodologies for stormwater control measures (SCMs) in respects to TSS can vary greatly. There are many sediment characteristics that should be considered when evaluating a SCM for TSS removal performance to ensure apples and apples are being compared among removal efficiencies for SCMs.

All Stormwater Particles Are Not The Same. Part 1: Particle Size And Composition

The EPA selected a removal standard of 80% total suspended solids (TSS) removal as the target pollutant of concern due to high TSS concentrations impact on water quality and degradation to aquatic habitat. Many other pollutants of concern are particle-bound, and TSS is thereby a surrogate for other pollutants. Testing methodologies for stormwater control measures (SCMs) in respects to TSS can vary greatly. In part two, we’ll continue our look at stormwater sediment and discuss particle shape and density and their affect on TSS removal.

Bioretention Part Three: Lessons Being  Learned – Siting Issues and Inlet Design

Not done with siting issues yet, maybe this becomes five parts? One issue on siting and design is the hydraulic grade lines. Recall from your road drainage days the equations that were used to space catch pits and throat openings? The equations allowed for you to estimate gutter efficiency and top width for specified design storms. Well, these equations still apply, and I am thinking maybe even more considerations for very low flows.

Bioretention Part One: Lessons Being Learned

As bioretention becomes more popular, many types of designs are being deployed throughout the U.S.  Though relatively simple in concept, many are finding that the devil is in the details with respect to maintenance and performance.  These issues are driving newer designs and improving criteria for use. Over my next few posts, I will be sharing some of the experiences and lessons learned with bioretention design. 

 

Top 11 Acronyms Every Stormwater Engineer Should Know

We are an industry of abbreviations and acronyms. The terms we use on a daily basis can sometimes hold a general or broad meaning in our minds, but the actual definition of these terms may leave our thumbs hovering over the game-show buzzer. To help ease the furrowed brows, we have collected and defined the top 11 terms every Stormwater Engineer should know:

Categories: Regulations
EPA Guidance Provides New Options for Meeting TMDL Goals

The goal of the TMDL program is arguably simple - to develop watershed level conservation plans designed to restore impaired waters and attain applicable water quality standards – but its development and implementation has not been simple. In an attempt to bring new clarity to the process of incorporating TMDLs into stormwater permits, the EPA issued a revised guidance document last November entitled “Establishing Total Maximum Daily Load (TMDL) Wasteload Allocations (WLAs) for Storm Water Sources and NPDES Permit Requirements Based on Those WLAs”.

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