The Stormwater Blog 

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

What Kind of Trash and Debris is in Stormwater Runoff?

We all know that stormwater runoff carries trash and debris into our water ways, but have you ever wondered what kind of material this runoff picks up?

A Contech Continuous Deflective Separation unit (CDS) was installed on a site in California and the performance of the unit was monitored over a 12 months.  During a maintenance event, the trash and debris that was captured by the CDS was removed, and the contents were separated and characterized. 

Stormwater in the west: Use it or lose it!

At about 2.5% of the total water volume on the planet, we’ve always had roughly the same amount of freshwater. Unfortunately, it seems that, at the local level, the amount of fresh water made available through precipitation is increasingly erratic, with the last year featuring historic floods in the eastern US and historic drought in the west. In my adopted home state of California, 2013 was officially the driest year on record and snowpack, groundwater and reservoir levels throughout the state are critically low. Although we’ve undertaken extensive engineering feats in the form of reservoirs, diversions and water supply pipelines, local water management decisions provide our greatest leverage on local water supply.

Stormwater Infiltration Explained

Stormwater infiltration is defined as the process by which water enters the soil and recharges streams, lakes, rivers, and underground aquifers. Stormwater infiltration is a fundamental component of the water cycle and is quickly becoming the centerpiece of stormwater management strategies across the United States. Stormwater infiltration is an effective means of managing runoff because it allows practitioners to address both water quality and water quantity concerns.

Stormwater Control Measures:  Are We Capturing All the Costs?
Most models and approaches toward cost accounting of Stormwater Control Measures (SCMs) use standardized engineering economics. These models use the first cost and annualized O&M costs, brought forward to present value using assumed interest rates, etc. Models that are more sophisticated will break the first costs down to show engineering design, project administration, land, and construction costs. O&M costs can be segmented for minor and major operations. In some models, costs are estimated from a statistical database based on costs from other projects. For example, the cost of pond maintenance is estimated on data from ten case history’s which are normalized to the area of the pond. Others are based on unit costs of labor, equipment, disposal costs, administration, etc. Each method has its advantages and drawbacks. However, my guess is that both methods lack the precision that people are looking for, and is some cases, are underestimating or overestimating costs.
Phosphorus Leaching from Bioretention and Green Roofs: The “Dirty Little Secret”

Bioretention and green roofs have become the centerpieces of Low Impact Development (LID) initiatives throughout North America. The well-publicized benefits of these two types of stormwater management practices focus on runoff reduction, stormwater quality treatment, and landscape aesthetics. Promotional literature provided by various regulatory agencies and environmental organizations typically highlights the processes and mechanisms within bioretention and green roofs that provide desirable outcomes. Normally, one finds mention of evapotranspiration, filtering, and adsorption characteristics of the vegetation and soil mix as beneficial mechanisms for the purposes of runoff reduction, particulate and hydrocarbon removal, and dissolved pollutant capture, respectively.

Three Steps to Evaluate Stormwater Filtration System Hydraulics

System hydraulics refers to how water flows through a stormwater filtration system. The following three steps should be part of the hydraulics evaluation process.

Categories: Treatment
When Conventional Bioretention is Not Feasible, Consider Tree Box Filters
Perhaps the most recognized Low Impact Development technique, bioretention, incorporates landscaped features to slowly percolate stormwater runoff through plants and engineered soil prior to infiltrating that water into native soils.
Evaluating Media for the Filtration of Stormwater

During the past decade, a number of different media have been used for stormwater filtration and more recently for bioretention. Media such as sand, peat, and compost have been used successfully. Uses of perlite, zeolite, carbon, and other "exotic" media have expanded the choices for targeting specific pollutants. Media are now being used to target TSS, Petroleum Hydrocarbons, Dissolved Phosphorus, dissolved metals and even bacteria. More recent research in biofiltration adds elements of biological uptake of nutrients and metals by plants, conversion of Nitrogen into ammonia in anaerobic zones.

Categories: Treatment, Filtration
Is Green Infrastructure Diminishing Innovation?

Since the Environmental Protection Agency, and in turn state and local regulators, have gone all in on green infrastructure (GI) and low impact development (LID) concepts a seemingly regrettable consequence has emerged.  Topics specific to the broader adoption and implementation of GI have monopolized our collective dialog on stormwater management of late.   The predominantly positive press and barrage of GI heavy conference agendas seemingly suggest that if we apply GI far and wide then water quality impairments caused by urban runoff will soon be a thing of the past.  GI provides stormwater practitioners with invaluable tools to aid in the stormwater fight, but many site specific challenges can’t be surmounted with GI solutions alone.  To that end, should we be concerned that overemphasis on GI is discouraging innovation?

Three Maintenance Tips For Your Rainwater Harvesting Cistern
All stormwater systems need to be maintained to continue operating effectively, and rainwater harvesting (RWH) is no exception. Unfortunately, many owners do not care that their stormwater BMP is not functioning due to lack of maintenance. Maintenance of RWS systems is critical for owners that depend on their continued operation and associated utility savings. Proper maintenance of a RWH cistern helps protect water quality and ensure system performance.
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