The Stormwater Blog 

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

Leave the Bio in BioFilter...Plants Do Matter
Plants provide fresh oxygen to breathe and beautiful aesthetics that can take our breath away, but many people don’t think about the role plants can play in stormwater treatment. The principal notion of Low Impact Development (LID) is founded upon mimicking pre-development conditions. Part of mimicking pre-development conditions includes not just matching pre-development peak flow rates, but also matching the pollutant load discharging from the drainage area.
Hydrodynamic Separation Devices: Online Vs. Offline
The question of whether a hydrodynamic separator should be online vs. offline is something that engineers and stormwater treatment manufacturers deal with on a daily basis.  Online systems allow storm events that are greater than the design storm to be bypassed through the treatment unit, eliminating the need for a separate bypass structure.  This results in fewer structures and a smaller system footprint; which leads to a lower landed cost.  
Designing CMP Detention Systems Part Three – Design Red Flags
In our third and final part of our blog series we will look at design red flags for CMP detention systems. Red flags are design elements that are commonly or easily overlooked and may need extra attention when designing. Considering the red flags upfront will expedite the design and fabrication process, and eliminate delays, installation, and performance issues.
Designing CMP Detention Systems: Part Two – Cost Effective Design and Layout

The goal of any CMP detention system should be to maximize the vertical space available to minimize the overall footprint, to reduce material, excavation, and backfill costs. To do this we recommend using the largest diameter pipe possible.

Designing CMP Detention Systems: Part One – The Value of Going Underground
The two essential functions of a stormwater management system are to control the quality and quantity of runoff leaving a site. There are various ways to do this; a common method is with an above ground system in the form of a detention pond.
Maintenance Resiliency of Stormwater Treatment Facilities
With the passage of time and the placement of stormwater treatment facilities into service in urbanized areas, it’s been possible to observe how these facilities age. All too often, the majority of effort and focus is placed upon the design and construction of stormwater treatment facilities, which are often neglected or forgotten once construction is complete. Depending on circumstances, this often results in deferred (if not nonexistent) maintenance of these facilities, which only worsens with time as the facilities age and accumulate collected pollutants with each passing year.
Categories: Maintenance
Rain Gardens Not Permitted?

Current stormwater design guidance typically recommends starting with preservation of the natural landscape and hydrology wherever feasible. But, even with preservation, new stormwater management facilities are likely to be required to capture and clean runoff from pollution generating surfaces. These new stormwater facilities are likely to include imported soil or soil amendments that add permeability and/or optimize soil structure for vegetative growth. For many years, the industry has characterized media in vegetated facilities generically as soil, sand, compost, etc.

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.

Rainwater Harvesting and Make Up Water: The Why, When, and How

Rainwater harvesting (RWH) stores rainwater for reuse to supply non-potable uses like irrigation, wash water, toilet flushing, and laundry.  During long dry periods the demand will drain the storage cistern down to a critical level where the pressurization pump(s) will need to shut down to prevent dry run damage.  Make up water is typically a potable connection to the rainwater harvesting system to supply water, allowing the RWH system to continue to supply the non-potable end use applications until the next storm event refills the storage cistern.

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