Meeting Minutes and Agendas

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What's Happened?

Stormwater Program

A Stakeholders Advisory Committee (SAC) was formed in late 2015 to begin addressing the stormwater needs of the Township and determine an equitable fee structure to fund those needs. The SAC identified over $27 million in stormwater improvement needs and determined a Stormwater Program Fee based on impervious area (IA) was the most equitable way to fund the program. Impervious area is any surface which inhibits infiltration of rainfall into the soil. This includes pavement (asphalt, concrete, etc.), rooftops, patios, sidewalks, and compacted graveled surfaces such as parking areas and driveways. Numerous studies have shown that IA is a strong indicator of both the quantity and quality of stormwater.

Once the Stormwater Program Fee method was determined, an analysis of the Township's IA was conducted. This information was used to calculate a fee. The fee is based on an Equivalent Residential Unit (ERU), which was statistically determined to be 3,800 square feet. The DTMA Board initially set the fee at $6.50/month/ERU. This fee was calculated by taking the monetary costs to run the program and dividing by the number of ERUs in the Township. The DTMA Board set the fee implementation date as January 1, 2017. Beginning in January 2017, property owners in Derry Township with a minimum of 500 square feet of IA began receiving a stormwater program fee bill. For those property owners who already receive a sewer bill, the stormwater fee became a new line item on that bill. Those property owners who were not connected to the public sewer still received a stand-alone stormwater bill. For the typical residential home (1 ERU), the stormwater fee was $6.50 per month ($78.00 annually). For non-residential properties, the stormwater fee was calculated by dividing their total IA by 3,800 square feet to determine the number of ERUs. The number of ERUs were then multiplied by $6.50 to determine the monthly charge. For example, a commercial property with 19,000 square feet would equal 5 ERUs (19,000/3,800 = 5). That property's monthly fee was 5 x $6.50 = $32.50 ($390.00 annually).

With the time that has passed since 2017, costs have naturally risen, and DTMA’s list of projects completed and planned has grown considerably. To meet the ever-increasing commitments of the Stormwater Program, DTMA has seen the need to raise the fee to $9.50/month/ERU.

Fall Fertilization

How You Manage Your Lawn Matters

Did you know that 90% of residents within the Chesapeake Bay watershed live within 0.5 miles of surface water and that turf is the #1 “crop” in the Chesapeake Bay watershed? That means how you manage your lawn matters, as it is highly likely to end up in a nearby surface water that eventually makes it to the Bay. Even if we weren’t in the Bay watershed, our local streams are receiving those pollutants, so it’s important to keep that in mind when conducting lawn maintenance.

Chances are, you only need to apply fertilizer once a year (or not at all), and that time is now. Fall is the perfect time to apply fertilizer. Listen, you aren’t a bad person if you fertilize more than once a year or for that matter if you don’t fertilize at all. Assuming you aren’t bagging and removing the clippings, chances are your lawn may not even need fertilized because those clippings act as a slow release fertilizer. Don’t overdo it when you do fertilize, you shouldn’t apply more than 0.9 pounds of total nitrogen per 1,000 square feet. Speaking of square feet, make sure that area only includes your lawn! If you get some fertilizer on the sidewalk or your driveway, take a broom or use a leaf blower and get it back onto your lawn. If your lawn is adjacent to a surface water body, leave a buffer when you fertilizer of about 15 feet.

Not sure if you need to fertilize? Get a soil test done for your lawn. Besides telling you what nutrients you might need, the soil test will also tell you if your soil is too acidic and needs lime. Lime helps raise soil pH and can make certain nutrients more available for uptake by plants. The only thing a soil test can’t measure well is nitrogen. However, good news, you can do that yourself. Nitrogen helps keep plants looking green, so just peak out your window and see if your turf is looking yellow. Be careful though, we’re not talking about the kind of yellow that develops when the turf goes dormant during dry spells, we’re talking about the kind of yellow that appears when your neighbor’s lawn looks green and lush and yours isn’t. Remember, smart turf maintenance is good for the environment and your wallet!

Stormwater Basins

A Closer Look

We’ve all seen them, the open grassed areas adjacent to development that look like a pond that someone forgot to fill with water. Then it rains, and that dry open area fills with stormwater. Then days later, it’s empty again. Obviously, the basins were designed to hold stormwater, but why do we need to hold stormwater and how do these basins drain once they fill up?

Although basins may all look the same, there are actually several different types. One type is known as a retention pond. Retention ponds are designed to constantly hold water. We’re going to focus on two other types of basins that are designed to momentarily hold water – detention and infiltration. Detention basins are designed to allow stormwater to enter and then exit through a small hole or orifice. The orifice is sized to send the water out at a rate that won’t aggravate downstream flooding and that won’t allow the water to hang around too long and be a breeding ground for mosquitos. The water that leaves a detention basin eventually makes its way to a stream.

An infiltration basin allows water to enter just like a detention basin, but does not have an outlet orifice to allow water to exit the basin. Stormwater that enters an infiltration basin must exit by infiltrating into the underlying soils (hence the name). As we’ve discussed in a past Stormwater Minute, stormwater that enters the soil gets physically filtered by the soil and chemically and biologically filtered by the microbes that live in the soil. That filtered water eventually makes its way into the groundwater, helping to replenish that valuable underground resource. Remember, both detention and infiltration basins hold back a volume of stormwater so that it doesn’t aggravate flooding. Detention basins let the captured water enter a stream at a controlled rate, and an infiltration basin returns that water to the groundwater aquifer. So next time you walk past a stormwater basin, see if you can tell if it’s a detention or infiltration basin.

Water Flow in Soils

Water Flow Through Soils on a Local Scale

We've talked about landscape-scale water movement and how that affects our Stormwater Management Program. Now we’re going to look at how water moves through soils on a local scale and how those mechanics can affect water quality. We’ve mentioned before that soils have pores: space in soils where air and water can go. When it begins to rain, water moves into soil pores through unsaturated flow. Unsaturated flow means the pores in the soil are not completely full of water. As it keeps raining, more and more water moves into the soil pores until they fill up, or in other words, become saturated. At this point, we refer to the movement of water as saturated flow.

The pores in soils come in all sorts of shapes and sizes. Some pores are small and some are big. As you can imagine, big pores can move more water and move it faster than small pores, just like highways move more cars faster than local roads. Water only moves through big pores during saturated flow and does so under the influence of gravity (water flows downhill). In unsaturated flow, water is pulled toward the soil by forces of attraction (not the romantic kind) that are greater than the force of gravity. If you’ve ever stuck a sponge in water and watched it soak “up” the water, you’ve seen this principle in practice and witnessed “water flowing uphill”.

When we concentrate stormwater on a landscape we create conditions that lead to saturated flow, which leads to water quickly moving through soil by gravity, and potentially not having enough time for the soil microbes to help breakdown and retain some of the pollutants. When we spread stormwater across a larger land area, the water is pulled into the soil by attractive forces associated with the soil particles and unsaturated flow occurs. Because the soil is “pulling” the water, the water and associated pollutants are retained in the soil longer allowing microbes time to breakdown the pollutants. Think about that next time you forget to turn off your lawn sprinkler!

Water Movement

Over Landscapes & Time

Have you ever stopped to think about how water moves across a landscape? Some may say, “water flows downhill”, which is often but not always the case (stay tuned next time for more on that). The reality is that when our brains start trying to conceptualize something complex, we tend to find a way to simplify it for easier comprehension. That’s fine for general thinking, but when we start trying to address issues like flooding and water quality, how we frame our solution is dependent on how accurately we conceptualize the problem.

Enter Variable Source Area (VSA) Hydrology, the concept that the majority of runoff exiting a watershed is driven by a relatively small portion of the watershed. When we talk VSA hydrology, we use terms like saturation excess overland flow and infiltration excess overland flow. Stay with me, as it will all become as clear as mud soon enough. Saturation excess flow occurs when the soil becomes saturated and any new precipitation cannot enter the soil because there’s no more room in the soil pores. Think of this as trying to get tickets to a sold-out concert. The venue can only serve so many people that day, all others have to go find something else to do. Infiltration excess flow occurs when the rate of precipitation exceeds the infiltration rate of the soil. This is like trying to go out to eat at a restaurant but there’s a 45-minute wait. The restaurant can eventually feed you, but you’ll probably move on to another restaurant instead of waiting. When precipitation hits saturated ground or falls faster than it can infiltrate into the soil the excess becomes runoff and that’s the focus of a Stormwater Management Program.

What VSA hydrology shows us is when and where each type of flow is dominate on a landscape, just like a schedule of community events tells us when and where traffic might be an issue. Stadium owners don’t staff their parking lots 24/7 because they don’t host concerts and sporting events 24/7. Doing so would be an inefficient use of their resources. The same principle applies to mitigating the effects of stormwater. If we understand how water movement occurs across a watershed we can focus our resources on the areas where they’ll be most effective.

Stormwater & Vacations

Stormwater Ruined My Summer Vacation

Maybe you’re planning a trip to the beach, a lake, or even the Summer Olympics in Rio De Janeiro this summer. Trips like those are a great way to unwind from the stresses of life and partake in some great outdoor fun. Unfortunately, many of our favorite destinations are experiencing the ill effects of inadequate stormwater management.

The Summer Olympics are being plagued by reports of poor water quality in some of the same waters our athletes will be competing. Reports of bacterial and viral concentrations as high as 1.7 million times levels acceptable in U.S. waters have been reported. Additionally, reports on the presence of garbage in the water indicate rowing and sailing teams are having to navigate around such things as couches, television sets, and other discarded items.

Myrtle Beach South Carolina has been under a Long Term Advisory from the State Department of Health and Environmental Control warning people that swimming is not advised in areas around stormwater outfalls because of high bacteria levels. Florida’s “Treasure Coast” is experiencing a massive toxic algae bloom which has caused Florida’s governor to declare a state of emergency in some counties and even ask for help from the Federal Government. The algae bloom stems from Lake Okeechobee, where nutrient- and pollutant-laden runoff caused the formation of an algal bloom that was released to the ocean when the Army Corp of Engineers were forced to discharge water from the lake to avoid the potential for flooding from recent high rainfall events.

Unfortunately, these events aren’t isolated or uncommon. The list could go on and on. The point is that if we don’t focus on the issue of stormwater management when it’s a small problem, we will eventually get smacked in the face when it is a big problem. Big problems are always costlier to repair than small problems. If you don’t believe me, just ask the elected officials in Brazil, Myrtle Beach, and Florida.

The Root of the Solution

The Role of Plants in Stormwater Management

Stormwater is managed for quantity and quality, and plants play a major role in improving both. It’s no secret that plants provide ecological benefits, but sometimes we forget how crucial they can be in an effective stormwater management strategy.

When we employ engineered stormwater strategies, we are really trying to mimic some of the benefits plants provide a watershed when precipitation occurs. Picture in your mind the difference in water quality of runoff coming from a forested tract of land versus a recently plowed farm field. Neither of these land uses contain any impervious features such as houses, parking lots, or sidewalks, but the difference in runoff quality and quantity is striking, and a powerful example of what plants provide in an ecosystem.

In the past, stormwater management strategies attempted to mitigate the effects of plant removal by storing and slowing releasing stormwater from a developed site (think detention pond). Although that type of stormwater best management practice (BMP) can provide some benefits, the beneficial utilization of plants is unfortunately missing. Today, there are many ways site developers can incorporate the power of plants into an overall stormwater management strategy.

The strategic placement of trees, shrubs, and other plantings can help slow down and capture some of the precipitation adjacent to impervious areas of the site as it falls to the ground, eventually returning the water into the atmosphere through evapotranspiration. The placement of vegetated swales can help direct the flow and infiltration of stormwater along portions of the site while also providing an opportunity for nutrient and sediment uptake. The use of rain gardens or bioretention BMPs can replace traditional open detention or infiltration basins, providing similar but much improved water quality function. Beyond all of that, plants provide for an aesthetically pleasing landscape and provide much needed habitat for a whole array of wildlife.

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Meeting Minutes

And Agendas

Meeting Minutes

Agendas

Protecting & Enhancing

The Water Environment

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What's Up Next?

Stormwater Program

What's Happened?

Stormwater Program

Fall Fertilization

How You Manage Your Lawn Matters

Tropical Storm Lee

Extensive Flooding & Property Damage

Stormwater Basins

A Closer Look

Water Flow in Soils

Water Flow Through Soils on a Local Scale

Water Movement

Over Landscapes & Time

Fixing Soil Compaction

"Sometimes You Just Can't Turn Back the Clock."

Soils Need to Breathe Too

Did You Know Soils Breathe?

Stormwater & Vacations

Stormwater Ruined My Summer Vacation

Connecting the Stormwater Dots

Source Versus Transport

Haste Makes Waste

The Role of Time in Stormwater Management

The Root of the Solution

The Role of Plants in Stormwater Management

The World's Largest Filter

The Role of Soil in Stormwater Management