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Enjoying a spectacular fall in Portland, Oregon leads me to talk about street trees and leaves.As we all know the value of trees extends well beyond stormwater management.  Urban trees provide numerous benefits including providing wildlife food and habitat,  reduction of the heat island effect (up to 4 degrees C)  and reduction in CO2 emissions and

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

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As a volume based stormwater control measure, bioretention systems are providing beneficial use in that they reduce runoff volumes and peak flows. In areas where combined sewers are an issue, bioretention can reduce CSO frequency while increasing evapotranspiration and helping with groundwater recharge via infiltration processes. Common design

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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

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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,

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System hydraulics refers to how water flows through a stormwater filtration system. The following three steps should be part of the hydraulics evaluation process.1. Evaluate the hydraulic grade line (HGL) at the design flow rate. Typically, a backwater calculation from the point of downstream control should be performed to ensure the system can

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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

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As the need for effective stormwater treatment and volume control grows, so does the number of available stormwater control measures (SCMs) such as filtration systems, hydrodynamic separators, bio-retention  systems, green roofs and pervious pavement. As part of their due diligence, engineers go through an evaluation process to determine if the

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Having worked in the field of stormwater management for almost 20 years, and seeing the conceptual and technological development of stormwater management and BMPs, it is clear we have had successes and failures.We need to learn from both, especially with USEPA’s national rulemaking activities to establish a program to reduce stormwater discharges

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The removal of site-specific pollutants can be maximized with the variety of filtration media available. Understanding the hydraulics of the media you choose is a key, albeit misunderstood, factor in determining the effectiveness of the filtration system. Here are five things you should consider.1) Evaluate the specific flow rate (q) through the

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