• When you are talking about hard roofs, are you referring to asphalt shingle roofs or steel?
  • Can you define a brown roof?
    • Brown roofs are similar to green roofs but have a primary goal of encouraging biodiversity. They often are constructed using locally sourced materials as the soil base, starting out with a brown, soil color and often allowed to populate with local flora and/or fauna, and are designed to accommodate a wide range of plants and animals. For more information, see 1, 2, and 3.
  • Could a system to harvest/clean gas station runoff be proposed as optional for a period of 5 yrs then mandated...the runoff of hydrocarbons is much more serious from the source points than imagined.
    • The Construction Stormwater General Permit prohibits infiltration when the infiltration system will be constructed in areas that receive discharges from vehicle fueling and maintenance. Stormwater harvest systems used for irrigation are not specifically mentioned in the current permit, but the irrigation water may infiltrate through the soil and into underlying groundwater. Treating runoff from gas stations is therefore not advisable. Some situations might be considered where a very carefully designed system is used. An example could be where advanced filters are part of the treatment system that remove hydrocarbons. A strategy used in industrial sites is diverting runoff generated from uncontaminated surfaces (e.g., rooftops) away from the contaminant source hot spots thus lessening the amount of runoff to manage and risk of contaminants being moved off sitre. In a harvesting & use situation it might be capturing roof runoff at the source and directing it to a beneficial use away from any contaminant hot spots. The manual does not discuss treatment methods for hydrocarbons.
  • Was groundwater recharge considered as a beneficial use?
    • Groundwater recharge is mentioned as a potential benefit of harvest systems due to reduced withdrawls. See here. However, harvest systems are unlike other stormwater infiltration practices in that infiltration occurs over a broader area rather than being focused, and water application may occur over a broader time period or be driven by plant demand. It is therefore likely that harvest systems, unless otherwise designed, will have a limited impact on groundwater recharge. In parts of the country such as arid or semi-arid areas, groundwater recharge has been described as a “use” where water supplies are limited and recharging aquifers is highly managed, most often with treated wastewater. In this case, it is usually referred to as Aquifer Storage and Recharge (ASR) with the aquifer serving as a “reservoir” and part of a constrained water supply system. Water is recharged for later withdrawal, often within a matter of months or just a year or two. The withdrawal could be for potable uses or agricultural irrigation. In our region, this ASR approach is not common. Wastewater from off site has not been a focus of recharge management, nor is an aquifer used as a short-term storage facility.
    • On a local scale and from a stormwater perspective, if a site has good recharge/infiltration potential, it likely is best to approach the project as an infiltration project (see Manual for Infiltration) and not try to create a harvest and use system that may be costly and challenged to hold and store water.
  • Are there any grant or assistance programs for this system?
  • Is there a tax benefit or rebates associated with this system?
  • How easy is it to get the maintenance supplies like the bulbs and filters?
    • It should be relatively easy to obtain these materials from vendors, but it is best to determine this during the design phase.
  • How is the waste stream handled from backwashing filters?
    • Unless deemed hazardous or restrictive for some other reason, wastes are typically returned to the sanitary sewer system.
  • We are working with a local historic business here in New Ulm right now who has approached us about the potential for a permeable parking lot, or something like water capture and re-use on site - all vs just paving the parking lot...is there anything or anyone we can talk to about comparing costs before taking on the cost of an engineer?
    • Unfortunately the cost information in the manual is fairly general. Costs will vary depending on several factors. Some of the studies included on the case studies page include cost information. The manual lacks information on costs for permeable pavement. There is likely some good information in the literature, however. For example see here. Searching the web and looking at appropriate case studies should provide sufficient information to get a general idea of costs to determine if harvest and use or permeable pavement are cost effective approaches. You may also want to consider your physical site, the goal/standard you are trying to meet, and what fits the situation better. Typically porous asphalt is best for sites with permeable soils/subsoils, since no vegetation is involved to take up or filter the water. Conversely, harvest and use is well suited if soil permeability (or contamination) is a constraint. A best management practice (BMP) put in a setting or situation not suited to that BMP can be costly and not very effective.
  • Does your cost analysis take into account reliability of the system? At what reliability do these become viable? Reliability = amount of water supplied by system instead of the city or treated water
    • If we understand the question correctly, a properly designed system, including sizing, does consider reliability, as defined above. A back-up water supply (called makeup water supply) is needed to meet demand when harvested water is not adequate to meet demands. see here.
  • Since reuse ponds aren't in operation all year, how do you justify meeting treatment requirements for the remaining months? Is it necessary to supplement treatment during these times?
    • It is true that some systems are taken off line during winter months, including some pond systems. Consequently, these systems may meet a performance goal during part of the year but not throughout the year. This is a problem we are currently discussing. For now, see this guidance in the manual.
  • Where is this treatment going to take place? Is it at existing Reclamation sites or is this something that would have regional sites to specifically treat the stormwater?
    • If we understand the question correctly and this is about scale, local vs. regional, harvest and use has been used well at a small, local sites as well as larger, regional scales, so scale alone is not necessarily a constraint.
  • Can you reiterate what portion of the presentation is updated information to the manual, vs existing? (I missed the audio from the start of the presentation.)
    • All of the information presented during the webinar is new or updated information.
  • Should a general amount of 1" be used for irrigation calculations, or should irrigation demand be based entirely on Potential Evapotranspiration?
    • The amount of water to be applied for irrigation should be determined in the planning and design phase. During the summer, potential evapotranspiration is greater than 1 inch per week (see here), so limiting irrigation to 1 inch per week during the summer would decrease the volume of water that could be retained. Because the calculator restricts use to the smaller of PET and the user-specified irrigation rate, except on A soils, the only reason for inputting a weekly irrigation rate would be to limit the amount of water applied during the summer. Therefore, to maximize water application on B, C, and D soils, it is best not to enter a weekly application rate.
  • Will the MIDS calculator account for the amount of water supplied by harvesting versus supplement by the City distribution system?
    • It is assumed that all water in storage is from stormwater. That water may be used for irrigation or nonirrigation purposes. The calculator does not account for other sources of water.
  • Item for consideration: Potential daily application of stormwater via irrigation should not be interpreted to dictate that the potential application be administered daily regardless of storm events. It is better to administer water related to a specific event and to dispose of the corresponding amount. Between rain events, application should return to supplemental water only (horticultural practice). ...when a system is used for both stormwater management and horticultural purposes.
    • Agreed
  • For those that are using a cistern on a small scale for farming in particular (if you have an accessable cistern underground), during the winter months the tank can be emptied and used for crop storage and season extension. That is an added benefit of this type of system that has a high dollar value for a farm.
    • Thanks.
  • How do you forsee the proposed DNR Appropriation permit affecting the use of these systems in private developments?
    • The DNR Stormwater Use Water Appropriation General Permit is still in development, however, any entity (public or private) may apply for a permit authorization under the DNR Stormwater Use General Permit if the project is located within a MS4 Permit – regulated entity. This is a change based on comments received by the DNR during the comment and review period in November 2016 about limiting the General Permit eligibility to only local government units. The DNR agreed and has changed the eligibility to any stormwater use projects within a MS4 Permit – regulated entity. The DNR Stormwater Use General Permit will be available for stormwater use projects that use more than 10,000 gallons per day or 1 million gallons per year. For more information about the draft DNR Stormwater Use General Permit contact Dan Miller, DNR Water Use Consultant, at 651-259-5731 or dan.w.miller@state.mn.us.
  • Does the manual include any updates on the draft DNR appropriations permit for stormwater use?
    • The manual does not include updates on the draft permit.

This page was last edited on 8 February 2017, at 17:12.

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