In partnership with Stormwater Awareness Week, Stormwater University hosted this webinar covering green infrastructure, featuring speaker Tom Mortenson, PLA, ASLA – site planner and landscape architect for raSmith.
The presentation reviewed various site planning and design techniques, approaches, principles, successes, pitfalls and roadblocks to designing, establishing and maintaining green infrastructure systems and how these landscapes can integrate with well-designed environments. The historical natural patterns of hydrology and landscape were reviewed and compared to impacted, manmade, designed and manipulated patterns of hydrology and landscape. The content shows how we can learn from history by taking our cues from nature when thinking differently about water when we use the mindset of “rainfall integration” with logical efficiencies and proven design methods.
The webinar is now available to view on-demand here, and below, you will find responses to some of the questions posed by the audience in the Q&A session at the end of the live webinar.
Audience: How do you combat the mindset of developers who are only going to see dollar signs when you use these bigger methods of GI?
TM: I hear you on this question. When GI was first being implemented, private developers treated it like a gnat flying around their heads. Some used a few small elements on their projects just so they could say they were being “green and sustainable” in their marketing. It was all greenwashing.
This has been changing over the past 10 years or so. When/if there are incentives and grants available for GI, developers will take notice (they think “free money”). There are also some mandates and regulations that require the use of GI depending on project size and location. As a design consultant, it is my job to inform them early on of the benefits and realistic expectations and ask the right questions. Do they have the qualified staff to maintain it? Are they aware of the short-term vs long-term costs? Are they committed or are they looking for a quick bling for marketing? I think the more the private development world can see the benefits and outcomes on other projects, they will open their minds and wallets.
Audience: Speaking of salt, what factors should be considered when high levels of chloride are detected in waterbodies due to the use of rock salt during winter?
TM: Salt is an issue, for sure. I often am told that I need to use “salt tolerant plants” -- usually the person telling me that has no clue what they are talking about. When using natives, there are some plants that can handle more salt than others, but like humans, that doesn’t mean they can take a ton of salt. There is no easy button here.
In the upper Midwest, some cities have tried to reduce the use of salt and other chemicals by adding other compounds, like sand, with some success. On some projects, when we know there will be a lot of salt use on the site and they do not want / have a wet pond, we will keep the bottom of the basin as open aggregate stone and sand mix to act as a trap for salt and suspended solids.
Audience: Are there any considerations regarding the surface water's contamination, in permeable pavement development?
TM: Good question. The stone system base below the permeable pavers needs to be designed to a technical standard that includes rate and infiltration. The test studies have shown that the base aggregates perform like a filter by binding many of the compounds to the stone base. That being said, the outfall of these systems also needs to consider whether an oil/water separator or some other device / system is needed to meet the standards.
Audience: How can we engage local government officials to create more flexible or supportive regulations that encourage regenerative design?
TM: I was once involved in a grant funded program to meet with several suburban municipalities around Milwaukee to see how we could incentivize and/or change their codes to allow for more resilient systems to address stormwater. While most of them were open to the idea, we heard from many of them that changing their existing municipal codes would be a costly and lengthy process that would include legal consult and commissioners to embrace this approach. Unfortunately, the people in charge do not always understand or see the value in doing so (until their neighborhood floods or their sewers back up into their basements.)
Audience: How can we get review agencies and civil engineers comfortable with 100% detention on-site, when the site and soils are suitable?
TM: It has been my experience that this approach is typically enforced or mandated by the county, city, planning commission or stormwater agency. Like the Pabst Farms project, I highlighted – the requirements for infiltration of all stormwaters is all on-site. The alluvial / glacial soils are suitable to make that a reality. If it was all hard pan blue clay, that would not be feasible.
Audience: Do you have any other lessons learned about maintenance of permeable pavers - specifically the reality of having to vacuum?
TM: Permeable pavers, like any paving system, require maintenance. Asphalt paving might be cheap going in, but it becomes very expensive to maintain over time when you consider seal coating, crack filling, restriping, mill and overlay and ultimate replacement after 30 years. Permeable pavers last much, much longer, but do require occasional vacuuming / sweeping and sometimes the small aggregate in the void spaces needs to be replenished. Still, if the property owner is intending on holding onto the property for a long time (i.e. a library, government building, nature center, etc.) the upfront investment is well worth it.
Audience: For Stream Management, removal of concrete without increasing width to allow for turns and meandering will wreak havoc. Is the project going to widen to allow curving and meandering? I assume 'no' because it’s already developed.
TM: In the Milwaukee watershed, the agency is looking at all potential options for storage capacity. Yes, some of the properties adjacent to the river tributaries are narrow, but they are looking at options for recreating alluvial areas and floodplain where feasible.
