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Stormwater as a resource

  • 1.  Stormwater as a resource

    Posted 07-03-2019 03:28 PM
    Hi!
    Has anyone come across any examples of stormwater being used as a resource (e.g. for irrigation, energy generation, or non-potable uses) rather than something to get rid off? Or is it too polluted to be easily used? I know of some small-scale implementations, mostly rain barrels.

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    Natalya Sokolovskaya P.E.,M.ASCE
    Wynnewood PA
    (323)382-6176
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  • 2.  RE: Stormwater as a resource

    Posted 07-04-2019 07:20 PM
    Substantial amounts of stormwater are diverted into artificial groundwater recharge facilities in Southern CA.

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    Andrew Sienkiewich P.E.,M.ASCE
    RETIRED
    Long Beach CA
    (213)4589627
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  • 3.  RE: Stormwater as a resource

    Posted 07-04-2019 07:22 PM
    If we think about stormwater on a macro scale, it is used as a resource everywhere.  But, I think that you are limiting your question to just run-off from urbanized areas.  There are many examples of stormwater being used for irrigation and other uses.  I am hoping to steer the conversation to a slightly different tack, so, please excuse me if I am not giving you information you are looking for.

    I feel that it is crucial that we think of stormwater as a resource in this period of climate change to help protect our streams and rivers.  Everyone has heard that rainfall patterns will change to a more intense and less frequent rainfall events.  With this change, isn't it likely that our streams and small rivers will see a reduction in the base flow levels?  Because of that, it would appear that more of our perennial streams will have drought like flows in the periods between rainfall events between flood level flows.  This situation would likely leave these watercourses with lower "normal" water levels making like more difficult for the current residents and users of those watercourses.

    My opinion is that storage of water in watersheds to help maintain base flows will be critical to preserving what we see as a healthy environment.  Infiltration is a method of storage that is currently favored by most regulation and standards.  But,  I am not sure that reliance on this measure alone is up to to the task since it will be applied to just developed/urbanized areas.

    Storage of water behind dams to support stream flows and provide water for other uses seems as if it will be a necessity.  There is a movement to abandon/remove dams to re-establish a normal flow pattern and normal migration of wildlife through watercourses.  There are dams do more harm than good and should be candidates for removal; however, I think it is time that we gave some thought to encouraging dam maintenance and construction as a resource to cope with some of the impacts of climate change.

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    Bart Clark , PE
    Warren, CT
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  • 4.  RE: Stormwater as a resource

    Posted 07-05-2019 10:18 AM
    Houston has a lot of examples of using wet stormwater detention ponds for local irrigation.  We call these the purple pipe systems because we require the pumped stormwater to be placed in purple pipes.  In order to use this source of irrigation, we need to:
    1. have a community committed to allow their water level in the wet detention pond to fluctuate.  This requires engineers to consider what the ponds look like in various states of empty.
    2. have a good source of stormwater storage.  You need about 40" of storage in Houston to irrigate on a normal year.  In wet years, we would need less, in dry years we would need more.
    3. have a community that is willing to pay some utility costs in return for not paying for others.  This requires the utility provider (generally a Municipal Utility District (MUD) to consider the benefits associated with selling stormwater for irrigation instead of treated groundwater or surface water.  In an area in which groundwater has a big surcharge (up to $3.00 per 1,000 gallons) it is often a no-brainer.
    4. unlike treated water, stormwater irrigation systems don't need as much redundancy, because if we don't irrigate for a couple days, while the system is down for unscheduled maintenance, no one really suffers.  It is generally an easy decision when the MUD has to upgrade their water system.  Double redundancy plus backup power supply verses single system pumping and no backup power supply but some extra "storm water line" generally sells pretty easily when the MUD is required to upgrade.
    5. Baseflow in Houston is all mostly shallow groundwater and wastewater now anyway, so except in a couple big watersheds (Lake Houston, Brazos), we have limited need to regenerate baseflow.  I understand California's needs too.  Perhaps if they stopped routing their surface water supply through the hottest part of the US in open channels, we could achieve higher efficient use of their water from Nevada/Arizona.  I know pumping it expensive, but 85-90% of the water from Arizona not making it to the end users should not be an acceptable standard.  I understand it is an acceptable legal standard based on western states water law, but should it be?

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    Dwayne Culp, Ph.D., Ph.D.,P.E.,M.ASCE
    Culp Engineering, LLC
    Rosenberg TX
    (713)898-1977
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  • 5.  RE: Stormwater as a resource

    Posted 07-06-2019 09:43 PM

    Dwayne, thank you for the detailed reply!

    I've seen purple pipes used to carry recycled wastewater in California. Do you know if the stormwater needs to meet any water quality criteria before it's used for irrigation?

    On No.4, why is it less of a problem if a stormwater irrigation system breaks vs. the treated water? Is it because something different is being irrigated, or because of the existing backup system?



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    Natalya Sokolovskaya P.E.,M.ASCE
    Wynnewood PA
    (323)382-6176
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  • 6.  RE: Stormwater as a resource

    Posted 07-07-2019 07:57 PM
    Natalya:
    In Houston, irrigation water is treated for bacteria by either UV or chlorine.  After chlorine you need dechlorination.

    If we do no irrigate for 2-3 days while fixing the pump, its not generally a big deal because plants don't expect to be irrigated on a schedule.  So, we do not generally required duplex or triplex systems.   For treated domestic water, backup systems are always required, because people die without drinking water, and when the pressure gets below 20 psi, it requires a boil water notice because the bacteria levels spike and chlorine levels drop off the map, it can cause systems to backflow, and it makes fighting fires difficult.

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    Dwayne Culp, Ph.D., Ph.D.,P.E.,M.ASCE
    Culp Engineering, LLC
    Rosenberg TX
    (713)898-1977
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  • 7.  RE: Stormwater as a resource

    Posted 07-07-2019 11:19 PM
    Dwayne,
    Thank you for the clarification. I just wasn't thinking about the 'treated water' in the context of domestic potable water, which, of course, it is.

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    Natalya Sokolovskaya P.E.,M.ASCE
    Wynnewood PA
    (323)382-6176
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  • 8.  RE: Stormwater as a resource

    Posted 07-06-2019 09:52 PM

    Bart, thank you for replying.

    The question came to my mind while driving by stormwater retention ponds in a new development, so urban and suburban environments were what I was thinking about. I was also thinking about stormwater that ends up in combined sewers. You are also right that the stormwater becomes a part of the hydrologic cycle, especially if it infiltrates into the groundwater or is released back to the receiving water.

    I came across this article on the future Sites reservoir in California in May issue of the Civil Engineering Magazine. Is it something similar to what you had in mind when talking about collecting wet weather flows to supplement dry weather base flow?

    https://www.civilengineering-digital.com/civilengineering/may_2019/MobilePagedArticle.action?articleId=1485526#articleId1485526



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    Natalya Sokolovskaya P.E.,M.ASCE
    Wynnewood PA
    (323)382-6176
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  • 9.  RE: Stormwater as a resource

    Posted 07-09-2019 10:06 AM
    ​I'd like to emphasize again, particularly in southeastern PA, stormwater from treated roadways and pavement surfaces should not be used for irrigation or infiltrated into soil.  Salts are harmful to crops and soil in the long term and infiltrating salt into groundwater increases salinity of streams year-round, degrading environmental conditions for native stream wildlife and promoting growth of invasive species (particularly Phragmites).

    Water contaminated with salts is better desalinated, or flushed directly to streams where it is at least conveyed more quickly to the ocean.

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    John Zollers EIT,A.M.ASCE
    Engineer
    AECOM
    Philadelphia PA
    (215)606-0408
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  • 10.  RE: Stormwater as a resource

    Posted 07-09-2019 01:13 PM
    John,
    Salt in the roadway runoff is definitely an issue. I've heard a presentation on PennDOT studying green stormwater infrastructure to treat runoff from I-95, and de-icing salt was one of the major contaminants, and a major issue affecting plant health in these systems.

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    Natalya Sokolovskaya P.E.,M.ASCE
    Wynnewood PA
    (323)382-6176
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  • 11.  RE: Stormwater as a resource

    Posted 07-05-2019 10:22 AM
    Do you have a particular context in mind?

    Pollution in stormwater is a concern for some uses - for example, street runoff in winter in southeast Pennsylvania tends to have high concentrations of road salt, and infiltrating that into the ground contaminates both groundwater and stream flow with salt year-round (an issue that appears to be completely ignored by design engineers and regulators alike).

    Water collected off rooftops doesn't have that problem and can sometimes be used as "gray water" supplies for flushing toilets and the like.  I suspect there's a lot of room for untapped creativity with stormwater management as long as those being creative are clear-eyed about the potential for unintended consequences.  I've wondered if collected rainwater could be used as a heat source / sink for building HVAC systems, but in the summer that could be course be a source of thermal pollution to water bodies, etc.

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    John Zollers EIT,A.M.ASCE
    Engineer
    AECOM
    Philadelphia PA
    (215)606-0408
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  • 12.  RE: Stormwater as a resource

    Posted 07-05-2019 04:51 PM
    Rainfall water harvest is the term frequently used. Climate change is making us think more on how to retain rainfall in urban areas to augment resilience in drought periods . Detention ponds, infiltration pits, permeable pavements help keep water underground storage to be used when needed. Roof collecting is also used in some parts with storage of these waters in tanks above or underground. There is, of course, concern for using it as "potable." It would have to go through a treatment process to ensure safety.

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    Jose Ochoa-Iturbe A.M.ASCE
    Dir/ School of CE
    Caracas
    58 582124074361
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  • 13.  RE: Stormwater as a resource

    Posted 07-06-2019 08:32 AM
    In Maryland, I have seen a number of different uses for rainwater including irrigation, steam generation for co-gen facility, and non-potable restroom use.  For any use other than irrigation, some processing of the water is required, typically some type of storage, filtration and disinfection.  Some regulations also require that dye be added to the system for restroom usage to indicate that it is non-potable and signs be posted.
    There have also been numerous applications through the the US in rural areas for potable use at single family homes.  These systems usually have large cisterns,  membrane filtration system, and UV disinfection.
    The EPA has a document available on-line, Managing Wet Weather with Green Infrastructure Municipal Handbook: Harvesting Rainwater Policies, that lists examples and high level descriptions.

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    Rosanna La Plante P.E.,M.ASCE
    Eng
    Columbia MD
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  • 14.  RE: Stormwater as a resource

    Posted 07-09-2019 01:13 PM
    Thank you, Rosanna,
     It's good to hear that rainwater reuse is prevalent in our wetter climate as well as drier regions.

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    Natalya Sokolovskaya P.E.,M.ASCE
    Wynnewood PA
    (323)382-6176
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  • 15.  RE: Stormwater as a resource

    Posted 07-08-2019 11:54 AM
    I am currently working on a project where we are collecting rainwater from roof runoff so that it can be reused for toilet flushing, washing machines, and irrigation.  My local jurisdiction doesn't have specific requirements for treatment, but Los Angeles County Department of Public Health does, and it is a helpful resource.  http://publichealth.lacounty.gov/eh/docs/ep_cross_con_AltWaterSourcesGuideline.pdf
    It outlines the different treatment requirements based on the source of the water and the intended re-use of it.

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    Susanne Cooper P.E.,M.ASCE
    Engineering Manager
    Jensen Design & Survey Inc
    Ventura CA
    (805) 654-6977
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  • 16.  RE: Stormwater as a resource

    Posted 07-08-2019 05:00 PM
    Some municipalities give reductions in stormwater fees for onsite stormwater capture/usage (rain barrels, irrigation, etc), but that gets a bit tricky.  In TN, there would only be 9 months of usable irrigation (don't irrigate in winter month).  Rain barrels have been geared more to the homeowners as a cheap, environmentally friendly way to irrigate, but they have their own set of issues (mosquitos, etc).  Rain gardens (and bioretention areas) are aesthetic (vegetated) stormwater features, which (when properly maintained), are a definite stormwater resource/perk.

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    Maria Price P.E.,M.ASCE
    Engineering Manager
    City of Chattanooga
    Chattanooga TN
    (423)643-5961
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  • 17.  RE: Stormwater as a resource

    Posted 07-09-2019 01:13 PM
    Susanne,
    Thank you for the link. There are some useful references in these guidelines.  Best luck with your project!

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    Natalya Sokolovskaya P.E.,M.ASCE
    Wynnewood PA
    (323)382-6176
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  • 18.  RE: Stormwater as a resource

    Posted 07-09-2019 01:17 PM
    Great questions and I like your line of thinking.  Rainwater can absolutely be a resource.  We work on many Living Building Challenge projects which require net zero water usage, which often means utilizing rainwater for toilet flushing, potable use, ornamental irrigation, urban ag irrigation, car washing, and/or maintenance wash down water.  The end use typically dictates the level of treatment necessary and the state or city often limit what end uses are allowed.  The Los Angeles reference already provided is a great one for both rainwater and greywater.  I would also check out the ARCSA manual for rainwater reuse.  Based on experience, don't let the fact that a given city/county/state not having a regulation on the books allowing certain uses of treated rainwater stop you from working with them to allow for it (that was poor grammar, but what can I say, I work with numbers).  Good luck!

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    Justin Lyon P.E., LEED AP M.ASCE
    Biohabitats
    Philadelphia PA
    (973)262-1819
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  • 19.  RE: Stormwater as a resource