Soaking up the Rain; Permeable Pavers for Overlook

Overlook Community Pool parking lot in Bethesda has a new look and a new job. Not only is it used for parking cars, but with the completion of the new permeable paver system, it’s providing stormwater management! A portion of the asphalt has been replaced with permeable pavers. This new surface allows the rain to soak into the ground as well as support cars. So, when it rains, the water will infiltrate instead of running off the parking lot, down the storm drain system and into the Little Falls creek. More information about the project is here.

How do the pavers capture rain water?

Permeable pavers are interlocking concrete blocks that rest on a specially engineered subsurface that allows for the rain water to be held in a large gravel bed until it soaks into the ground. The 15-inch uncompacted gravel bed is key to the whole system. The blocks themselves are not permeable, but contain spaces between them for the water to drain through. Once the water goes through the spaces, it flows in the gravel bed where it is stored until it can soak into the ground. The water usually empties within 24 hours. In the Overlook system, the gravel bed is designed not only to capture the rain that falls on the pavers, but also the water running off the asphalt.

How does this help the creek?

Any water that goes into the ground instead of into the storm drain system helps the creek. When it rains, water runs off parking lots, driveways, roof tops, streets and other impervious surfaces and makes its way to the storm drain system. In Montgomery County, the storm drains go directly to the creek via pipes that run under the streets until they outlet into the creek. Everything that is washed into the water by the rain - trash, oil, dirt, chemicals, dog wastes - is dumped into the creek polluting it. In addition, the volume and velocity of the stormwater run-off causes flooding, erosion and loss of vegetation along the creek banks, habitat for wildlife.

When water is captured by the permeable pavement system, there is less water going into the creek. Instead the water goes into the ground where it will help to:

  • Remove pollution as it is filtered and cleaned by the micro organisms in the soil

  • Recharge the ground water creating a reservoir of water for deep roots to access during times of no rain.

  • Control local flooding

  • Protect the local creek from erosion.

Learn more about the project HERE.

where else can pavers be used?

Permeable pavers are a great option for many residential projects, including driveways, walkways, patios, sidewalks, shoulder parking areas and pool decks. If you are interested in learning more about managing rain water on your property and the rebate program offered by Montgomery County and Washington DC, visit our rebate page.

Why the overlook pool parking lot?

The Overlook Pool Parking Lot Permeable Paver Project is the second project in a comprehensive storm water management plan for Overlook, a 99 household neighborhood which abuts the Little Falls Stream Valley Park and overlooks the Dalecarlia Reservoir. It all started in 2017 when the Overlook Homeowners Association noticed that the community pool parking lot needed resurfacing. But they also noticed that the Little Falls creek was experiencing a lot of run-off from the hilly community and erosion was causing serious problems where the storm drain outlets approached to creek. A little research by Overlook Board Member George Clark lead him to believe that they could help with the run-off problem when they redid the parking lot and maybe there were other areas where rain water could be made to soak into the ground. And so, the Overlook Stormwater management project was born.

George contacted the Little Falls Watershed Alliance and we were able to secure a grant to do a stormwater management study for the community which owns 6.2 acres of shared common space - including the community pool. The study identified nine areas where stormwater management could be done to reduce the impact of rain run-off on the Little Falls creek. Rain gardens, curb cuts, conservation landscaping and permeable pavers were on the list of green techniques that the neighborhood could use to manage and treat the storm water. The grant also included moneys to install two demonstration rain gardens. These gardens were sited in a very visible spot near the community pools to help with a considerable erosion problem that created a mud slide on the walkway, but also to show residents just how lovely rain gardens could be. Signage at the site highlights how rain gardens help with stormwater management and how they can be used on residential property.

Overlook projects reduce pollution and run-off

Together, the rain gardens and the permeable paver projects treat over 15,000 gallons of water when it rains. They reduce pollution by keeping 0.284 pounds of phosphorus will be kept out of the creek, 167.31 pounds of silt (TSS) and 5.99 pounds of nitrogen.

next steps for Overlook

The Stormwater management plan developed in 2017, provided Overlook with a road map for future works. If the entire plan is implemented, 11.74 acres will be treated with total removal of 4.26 lbs/year phosphorus and 106.89 lbs/year nitrogen and 3,311.60 TSS.  This would represent a 27% reduction of TP, a 22% reduction TN and 29% reduction in TSS for the neighborhood pollution load and a strong commitment to the environment by the residents. The next step is to revisit the plan and pick another to implement.   We look forward to continuing to work with Overlook on this important project.

The Overlook Stormwater Management Projects are made possible by two grants funded by the Montgomery County Water Quality Protection fund.

Mow Your Leaves for a Better Environment!

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It’s time for our annual appeal: Leave the leaves

Feed your lawn by mowing the leaves. It’s good for the environment and good for your lawn. We’ve been preaching the benefits of mowing your leaves for more than10 years now and it’s beginning to catch on! If you’re skeptical, just try it on a portion of your lawn, maybe a side yard, or behind the garage. To quote Scotts Fertilizer: “When spring arrives, you'll notice something: The leaf litter you mulched up in the fall will have disappeared. Meanwhile, your rake will look dusty and neglected—but your grass will look greener than ever.” Yes, even Scotts Fertilizer is recommending that you mow instead of raking (or blowing)!

Piles of Leaves Cause Problems Downstream

Big piles of leaves by the curb, a certain sign of autumn and lots of fun for kids to jump in. What could be wrong with that? Not to be the Grinch Who Stole Leaf Pile Jumping, but everything. Leaves in the gutter make their way to the creek where they decompose and cause nutrient bloom. Leaves in the gutter mean no leaves around the base of your trees where they provide an organic blanket for the trees during the winter. Leaves in the gutter mean you are wasting valuable nutrients for your lawn.

Mow, Don’t Rake!

So, this year, take a tip from Winterthur, the spectacular DuPont gardens in Delaware and mow your leaves right on the lawn.

From a Washington Post article

For more than 20 years, the gardeners at this expansive and famously leafy estate have been mowing leaves with (...) lawn mowers. The machines inhale the leaves, chop them into shreds and deposit them as the mower moves along. Engine noise is confined to the muted chug of the mower, not the incessant high-pitch whine of the leaf blower.And there are no bags to unhook and drag anywhere, just a confetti-like litter left on the grass. Ripped into morsel-size pieces, the flakes melt away in two or three weeks as microbes and worms do their work of enriching the soil.

It is such a simple system that (Chris) Strand, garden director, and Long, assistant garden curator, wonder why it hasn't caught on. They are certainly converts in their own gardens. "I spend a fraction of the time I used to spend raking and transporting leaves," says Strand.

This process is endorsed by none other than the Scotts Fertilizer Company. On their website, they recommend you

Take the grass catcher off your mower and mow over the leaves on your lawn. You want to reduce your leaf clutter to dime-size pieces. You'll know you're done when about half an inch of grass can be seen through the mulched leaf layer. Once the leaf bits settle in, microbes and worms get to work recycling them. Any kind of rotary-action mower will do the job, and any kind of leaves can be chopped up. With several passes of your mower, you can mulch up to 18 inches of leaf clutter.

So, give your rake a rest, save the local government some money and help the environment all by mowing your leaves. It works for the Winterthur Estates and it will work for you. When spring arrives, you'll see great results. The leaf litter you mowed this fall will have disappeared. And your grass will look greener than ever.

And if your children need a pile to jump it, rake them one and when they're jumped out, put those leaves under your trees and around your shrubs - free and beautiful mulch!

Great Lawn Fertilizer and Winter Habitat

The National Wildlife Federation states "In addition to becoming natural fertilizer for your soil, leaves that stay where they fall create “mini ecosystems,” according to another post by the group. Chipmunks, salamanders, earthworms, turtles and other small creatures live in the leaves or use them for food and nesting material, and butterflies and moth pupae like to spend the winter in the leaf layers."

University of Michigan Study Endorses Mulching

Here's another good article about mowing your leaves that sings praises to the value of mulching your leaves right on the grass.

http://www.mlive.com/homeandgarden/index.ssf/2012/10/mulched_leaves_offer_food_prot.html

The author addresses the problem of oak leaves - hard to mulch, but with patience, they will shred.

Fine Gardening Magazine Encourages Leaving the Leaves

Mowing leaves into your lawn can improve its vigor, and unraked leaves in planting beds don’t smother shade-tolerant perennials
by Terry Ettinger

If you dread the annual fall leaf-raking marathon, I have good news for you: Raking and collecting leaves every autumn is a tradition without scientific basis. Research has proven that mowing leaves into your lawn can improve its vigor, and observation shows that unraked leaves in planting beds don’t smother shade-tolerant perennials. Click HERE to read more.

Permeable Pavers for the Overlook Pool Parking Lot will Reduce Harmful Run-off

The first step in installing permeable pavers is to create a gravel reservoir to capture the rain water.  The pavers will cover the reservoir and rain water will pass through the spaces to be stored in the gravel until it can soak into the ground.

The first step in installing permeable pavers is to create a gravel reservoir to capture the rain water. The pavers will cover the reservoir and rain water will pass through the spaces to be stored in the gravel until it can soak into the ground.

Overlook Community Pool in Bethesda is getting a new look and stormwater management. Work has started on replacing 1,300 square feet of asphalt with permeable pavers so that the rain water can soak into the ground instead of running off the parking lot into the Little Falls creek.

In 2021, LFWA was pleased to received Montgomery County Watershed Restoration and Outreach Program Grant to tackle the problem of stormwater run-off at the Overlook Community Pool. Working with the Overlook Homeowners Association (OHA), the parking lot will be retrofitted so that it can capture stormwater instead of sending it to the creek.

Problem: Too much runoff

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Rain water was running off the Overlook pool parking lot into the storm drain system causing down hill flooding and sending toxic chemicals, trash and other pollution directly to the Little Falls creek. The volume and velocity of the storm water run-off is also causing serious erosion on the creek banks. The resulting silting in the Little Falls creek endangers the small creatures who make their homes under and on the rocks at the floor of the creek, making the Little Falls Branch one of the most impaired streams in the County.

Solution: Install Permeable Pavement!

Areas for pavers are shown in green.  The pavers were placed on the south end of the lot so that the tree roots would not be disturbed.

Areas for pavers are shown in green. The pavers were placed on the south end of the lot so that the tree roots would not be disturbed.

Based on the findings and recommendations of a 2017 stormwater management study for the Overlook community done by the Center for Watershed Protection, we worked with the Overlook HOA to determine how to best prevent rain water from escaping from the 9,000 square foot parking lot. The lot is lightly used by pool goers, but is used as a play space by community residents and for community gatherings. There is also a huge willow oak tree at one end whose roots run under the pavement. After a series of community discussions and a survey of community use, it was decided to install permeable pavement to replace some of the asphalt. Permeable pavement are hard surfaces that are designed to allow rain water to soak into the ground while still supporting cars and other vehicles. The parking lot could still be used as a play/gathering area and the pavers would be located along the east and west sides of the lot, avoiding the end with the oak tree so its roots would not be disturbed.

While there are many different types of pervious pavement, interlocking permeable pavers were selected for Overlook based on their price, ease of maintenance, and appearance.

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How do Pavers Work?

Permeable pavers are concrete paving blocks that rest on top of an 18-inch deep specially prepared reservoir. The reservoir is filled with layers of different sized gravel. When it rains, the water runs through the spaces between the blocks and is stored in the reservoir until it can soak into the ground. This way, not only is the water prevented from flowing into the storm drain system to the creek, but the chemicals and other pollution are filtered out by the gravel and cleaned up naturally by the soil. This infiltration technique also recharges the ground water replenishing the natural aquifers that our waterways depend on for clean water.

faqs

Can the pavers support rescue vehicles and other heavy trucks? Yes - the pavers are being installed at Overlook are rated for commercial vehicles. That was an important requirement for the contract. They can support long term parking too. In fact, in many places permeable pavers are used specifically for parking areas to distinguish the parking spaces from the road.

Are the pavers handicapped friendly? Yes, the pavers are 100% ADA compliant. The surface should not present any problem.

Do the pavers need any special maintenance? Yes, but not that much! The spaces between the blocks must be blown out from time to time so that they do not become clogged. These spaces are critical to the function of the system and if they are blocked, the water cannot soak into the reservoir. Further, snow from plowing and leaves cannot be stored on the pavers. Again, anything that could cause the pavers to clog should be avoided.

Is there a residential use for pavers? Yes, permeable pavers are perfect for stormwater management on residential properties and can be used for driveways, walkways and patios. Use them to prevent flooding in your own yard, or prevent water from flowing into your basement. Visit https://www.lfwa.org/pervious-pavers to learn about area rebate programs.



The project is made possible by funding from the Montgomery County Water Quality Protection Fund.

Creeks have HIGH levels of E. coli bacteria

Board Member Sara Robinson demonstrating how to take a sample during volunteer training session, July 1.

Board Member Sara Robinson demonstrating how to take a sample during volunteer training session, July 1.

In a new program designed to inform the public on the safety of the creeks for recreation,  the Little Falls Watershed Alliance is monitoring the bacteria count of the Little Falls and the Willett Branches. On Wednesday, July 7, LFWA monitored the e.coli levels at four locations in the watershed

Two locations passed, two locations failed

Passed:
Little Falls Branch above the Somerset Pool – (217.8 MPN/100mL)
Little Falls Branch in Brookmont – (275.5 MPN/100mL)

Failed:
Little Falls Branch by the second bench below Mass Ave (648.8 MPN/100ml)
Willett Branch below the Bethesda Pool (579.8 MPN/100mL) 

Pass/Fail interpretations are based on Maryland and the District of Columbia's water quality single-sample standards for E. Coli in surface waters.  Water-bodies with E.Coli levels above 410MPN/100mL  are considered unsafe for human recreation.   

We will be testing sites along the two creeks every two weeks between July 7 and September 15.. Results will be posted on our website and on our Facebook page and shared with community list servs.

Visit HERE for more information.

Thank you to our team of trained volunteers for their commitment to this project. Thank you to the Anacostia Riverkeeper for analyzing the samples in their water quality lab and their help in setting up the program.

Volunteers Needed to Monitor Creek

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Little Falls Watershed Alliance is excited to announce that we are starting a bacterial monitoring program for the Little Falls and Willett Branches. We will be sampling at three sites to determine bacteria (E. Coli), pH, water temperature, and air temperature in order to provide up-to-date water quality information for residents during the recreational season. The results will be posted on our website and Facebook page for the public to access.

Citizen Scientists Needed

The key to the program is volunteers. We have selected three locations for testing and we need two or three people to adopt a location to do the sampling. The samples MUST be taken Wednesday mornings and they are sent to the Anacostia Riverkeeper’s lab for analysis Wednesday afternoons. All volunteers must attend a short training session.

Please contact us at stormwater@LFWA.org if you are interested in helping out.

why Monitor?

While the water of our creeks is mostly odorless and looks sparkly clear, the creek is one of the most impaired in Montgomery County. As an urban creek, located in a heavily paved area, stormwater run-off carries a toxic mix of chemicals, trash and other pollutants into the creek. Dog poop left on lawns or dropped into the storm drain system pollutes the creek with fecal matter. The storm drain system flows directly to the creek and after it rains, the volume and velocity of the water is so high that it causes considerable erosion and collapse of the creek banks. Further, sewer lines located under the creek are often exposed by the erosion and leak or break. By testing the e coli levels in the creek, we will get an understanding of the extent of fecal pollution and how the fecal count is affected by rain events. Most important, we will be able to advise the public about the safety of the creek for wading and other water activities.

What else do we Monitor?

Benthic Macro-invertebrate Survey: Four times a year since 2016, LFWA has taken a census of the macro-invertebrate life of the creek. We look for diversity of species as well as total number. Using the Benthic Index of Biotic Integrity (BIBI), we are able to grade the health of the creek. Despite having some bio-diversity, our creek consistently rates poor, the lowest grade. Learn about our program HERE.

Salt Monitoring: Winter salting can cause the salinity of creek to rise, making the waters toxic to life. Since 2019, LFWA has participated in the Izaak Walton Salt Watch program. Information is HERE. In the winter of 2020/21, the salt levels spiked to lethal twice after snow storms.



Thank You Trash Stewards

With the County restrictions for group activities ending, we will be starting our groups trash pick-ups again. Starting on June 12, we will go back to our once-a-month Saturday morning workdays, meeting at 10:00 at the corner of Little Falls Parkway and Mass Avenue.  As in the past, we will have boots to lend as well as gloves, bags and grabbers. 

LFWA Receives Grants for Stormwater Management and Robots!

Little Falls Watershed Alliances is honored to be the recipient of two grants from the Montgomery County Watershed Restoration and Outreach Grant Program. One $33,000 grant will fund permeable pavement for the Overlook community pool to manage stormwater run-off that is causing considerable erosion and other problems in the Little Falls Stream Valley Park. A second $30,000 grant is for an innovative water quality monitoring project using autonomous environmental robots.

Stream Team Update: Spring Monitoring April 17

It was a beautiful day for being outside and LFWA’s Stream Monitoring team was excited to be in the water looking for the benthic macro-invertebrates that give us an indication of the health of the Little Falls Branch. The weather was beautiful; the results discouraging. We found only 8 different species of organisms - caddisfly larva, damsel fly nymph, sow bug, aquatic worms, black fly larvae, midges, minnow mayfly nymph, an Asian clam, and sow bugs - putting the creek on the upper end of “poor” for bio-diversity.

Plant a Tree for Earth Month

One of the most important things you can do for the environment is plant a tree.  Trees provide habitat for 100s of insects, birds and mammals as well as lower the urban heat index, suck up stormwater and release oxygen into the air.  University of Delaware Professor of Entomology and author of Bringing Nature Home, goes further and identifies trees as keystone plants for the food chain.  He writes “Take a keystone native plant like an oak tree. More than 500 types of caterpillars can eat that oak tree. That allows for a more complex and, thus, more stable food web.” https://www.udel.edu/udaily/2020/december/doug-tallamy-native-plants-food-web-insects-birds-survival-earth/

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As more and more trees are cut down to allow for development, planting trees private property becomes even more important.  Fortunately, the District of Columbia and Maryland recognize the value of trees and offer several programs for homeowners.

In Montgomery County:

  • Free Shade Trees:  Montgomery County will install shade trees and provide aftercare guidance —all for free.  Request a tree at https://treemontgomery.org/request-a-tree/

  • Free Buffer Bundle:  The State of Maryland has bundles of saplings for homeowners who live along or near a waterway.  It can even be a drainage ditch.  https://dnr.maryland.gov/forests/Pages/programs/Backyard-Buffer-Program.aspx

  • $25 Coupon:  The Marylanders Plant Trees program started in 2009 to encourage citizens and organizations to partner with the State to plant new trees. Citizens can still take advantage of the coupon program to receive $25 off the purchase of a native tree at 86 participating nurseries across the State. Find a participating nursery and print your coupon at https://dnr.maryland.gov/forests/Pages/MarylandersPlantTrees/Introduction.aspx

  • Free Saplings for Earth Month:  Montgomery Parks’ Arboriculture division is hosting two free tree seedling giveaways. Attendees will receive a minimum of 2 tree seedlings, one flowering tree and one shade tree. More available upon request while supplies last.  Two locations!

Seedling Giveaway at Black Hill Regional Park
Date: April 10, 2021, Time: 8 am-12 pm, rain or shine, in 15-minute time slots*
Location: Black Hill Regional Park, 20926 Lake Ridge Drive, Boyds, Maryland 20841. This event will be setup in the Shelter J parking area. Follow the posted signs to the event. You must register for a drive-through pick-up time slot by reserving a timed ticket,

Register for a pick-up time: http://mocoparks.org/SeedlingsBlackHill

Seedling Giveaway at Olney Manor Recreational Park|
Date: April 17, 2021, Time: 8 am-12 pm, rain or shine, in 15-minute time slots*
Location: Olney Manor Recreational Park, 16601 Georgia Avenue, Olney, MD 20832. This event will be setup in the Field #1 parking lot area. Follow the posted signs to the event.  You must register for a drive-through pick-up time slot by reserving a timed ticket.

Register for a pick-up time: http://mocoparks.org/SeedlingsOlney

In DC:

Salt in Creek Reaches Toxic Levels

During the past two months, LFWA volunteers have periodically measured salt concentration levels downstream from the Massachusetts Avenue overpass as part of a national Winter Salt Watch program sponsored by the Izaak Walton League.   On two occasions, February 3rd and February 14th, measured concentrations were near acute toxicity levels for biological life (i.e. macro-invertebrates), which the EPA cautions should not occur more than once during a 3-year period. A “fair” level that animals can tolerate is usually from about 90-150 ppm; anything over over 230 ppm means that the water is toxic at some level to animal and plant life. Over 860 is acute toxicity.

Learn more about our program HERE.

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Where Does the Salt come from?

Have you ever wondered what happens to the salt that is spread on the sidewalks, driveways, and roads in our neighborhood during a winter storm?  When it melts or is plowed off, the salt seeps into the groundwater or runs off into local streams and flows into the Potomac River.  While salt helps to melt or prevent the formation of ice and keep these surfaces safe, too much salt, also called chloride-based deicers, damages pavements and inhibits biological life in our streams. Salt is not biodegradable, accumulates over time, and has long-term corrosive effects and environmental impacts. 

In our winter sampling, you can see the effect of salting and winter storms. Both the >600 readings were taken after snow storms. The January 27 reading was done before the storm at a baseline reading. Download the results HERE.

How does this impact the creek?

Salt toxicity is likely to be one reason the Little Falls Branch is currently rated as having poor water quality. At the winter sampling of biological life by out stream monitoring team, not only did were there very few organism, we were also missing the diversity of organisms that are essential to the health of the creek. Results from our recent benthic macro-invertebrate sampling can be found here.

what can you do to prevent salt toxicity?

Salt keeps us safe, but too much salt is a problem. It comes down to spreading the right amount at the right time and sweeping up the excess after a storm.

On your property:

Montgomery County recommends homeowners:

  1. Shovel right away - don’t rely on salt to melt the snow.

  2. Use salt sparingly - More is not better. When applied properly, it doesn’t take much to get the desired results. 12 ounces (a coffee cup full) will do 10 sidewalk squares or a 20 foot driveway.

  3. Sweep up excess after the storm and save it for another day. This saves you money and keeps the unused salt from dissolving and polluting our waterways.

On the streets and public sidewalks:

Sweeping up excess salt is imperative to good salt management. If you notice salt spills, report them by calling 311. The County or DC Government will send someone out to clean them up. If they don’t, let your elected officials know.