By Courtney Ahnert, Clean Water Institute Intern, Summer 2021
It’s common practice to use fertilizer to help your garden grow to its full potential. However, the components of plant fertilizer that make it work so well also have some detrimental effects when they are used in excess and then allowed to seep into water sources through stormwater drainage and other forms of runoff. Fertilizer contains large amounts of nitrogen and phosphorus, and when these get into lakes and streams, they spur increased algae growth and plant productivity, which can choke out fish and other aquatic life and hasten eutrophication of lakes. However, there are fertilizer alternatives and ways to keep fertilizer out of our water that you can use to ensure the safety of your local watershed.
Compost is a great alternative to store-bought fertilizer, and you can make some at little to no cost! Simply get a bin or other large container and throw in leftover fruit and vegetable scraps, coffee grounds and used-up loose-leaf tea (roses especially love coffee grounds!), and eggshells (great source of calcium- make sure you crush them up before throwing them in your compost bin). Add some soil and earthworms to your compost bin too if you can, because earthworms are good at chewing up and processing scraps in order to turn them into soil faster. Compost helps naturally provide your plants with all the nutrients they need, without the big risk to waterways that excess fertilizer poses.
Raised Beds and Reasonable Fertilizer Doses
If compost is not an option for you and you must use fertilizer, there are a couple of ways that you can minimize the runoff/contamination risk while still having a fruitful garden. One way of doing this is to plant your garden using raised beds, which puts a barrier and a bit of distance between your fertilized soil and potential runoff areas. Another option to use in conjunction with raised beds is a proper dosage of fertilizer. A little fertilizer really goes a long way for your garden. A good rule of thumb is to use fertilizer sparingly, but frequently, because if you pile it on all at once, most of it will get washed away and harm waterways instead of nourishing your plants. Also, if possible, use natural fertilizer like bone meal or blood meal instead of synthetic fertilizers.
By Laura Coup, Clean Water Institute Intern, Summer 2022
According to the EPCAMR, when one inch of rain falls on an acre of impervious surface, such as a parking lot, it results in 27,000 gallons of stormwater runoff. In comparison, when one inch of rain falls on one acre of forest or wetland, it produces only 750 gallons of runoff. Impervious surfaces like roads, roofs, sidewalks, and driveways can result in large amounts of stormwater runoff in residential areas. This runoff carries fertilizers, pet waste, oil, pesticides, viruses and bacteria, and other harmful pollutants down storm drains and then into streams and rivers. The EPA estimates that pollutants carried stormwater runoff makes up around 70% of all water pollution. These pollutants have negative impacts on both the drinking water supply and aquatic life.
Homeowners can help reduce the stormwater runoff from their property by installing rain barrels and/or rain gardens. Rain barrels are a fairly low cost and simple way to reduce your runoff. A rain barrel is typically made using a 50- to 80- gallon plastic barrel and should be installed on a sturdy base platform along your home with the down spout going into an opening on the top of the barrel. There should be a spigot near the bottom to drain water for use and an overflow hose near the top. The average rain barrel costs between 100 to 200 dollars; however, the cost can be reduced when homeowners construct their own barrel.
Rain barrels capture stormwater runoff from the roof of your home and temporarily store it for future use. This rainwater can be recycled and used to water gardens, lawns, or plants or used for outdoor cleaning, among other uses. According to Penn State Extension, lawn and garden care accounts for around 30 percent of our average daily water usage. Rain barrels decrease the amount of household water used for these purposes, and in turn can help reduce water bills. Using rain barrels also allows stormwater to slowly soak in and infiltrate the ground rather than quickly runoff and carry pollutants into storm drains.
Rain gardens are another way to reduce the amount of stormwater runoff flowing from your property. According to the Natural Resources Conservation Service, the size of a rain garden should ideally be between 5- and 10-percent of the area of the impervious surface it is receiving runoff from. Rain gardens are typically planted in depressions or low areas of the ground, and can be located near downspouts, driveways, sidewalks, in yards, or anywhere where they can receive runoff water from impervious surfaces. They should, however, not be placed within 10 feet of building foundations and/or basements. The Groundwater Foundation recommends that your rain garden be longer than it is wide, and positioned perpendicular to the slope of the land so that it is able to catch as much runoff as possible. The deepest part of a rain garden should only be around six inches in order to allow the rain garden to properly drain between rain events. The depth should vary throughout the rain garden to allow water to flow and slowly fill up the garden.
Rain gardens ideally contain native species of flowers, shrubs and other plants. Native plants tend to have root systems better adapted to utilizing the water and nutrients available in local soils. Native plants will also help your rain garden attract beneficial birds, butterflies, and insects. Penn State Extension offers an excellent resource for determining which native plants can be beneficial additions to your rain garden (https://extension.psu.edu/rain-gardens-the-plants). Self-installed rain gardens generally cost between $3 to $5 per square foot, while the cost may increase to near $10 to $15 when using a landscaping company.
Rain gardens collect runoff during rainfall events and allow that water to percolate and slowly infiltrate the ground, rather than entering storm drains. In this process, the rainwater runoff is filtered by the plants and soil and helps recharge groundwater aquifers. The Groundwater Foundation estimates that rain gardens are effective in removing upwards of 90% of chemicals and nutrients and 80% of sediments from stormwater runoff. These pollutants would otherwise enter storm drains and go into our streams and rivers. Rain gardens also allow much more water to soak into the ground than a typical lawn.
One inch of rain graphic by EPCAMR
By Nidhee Seernaum, Clean Water Institute Intern, Summer 2022
Riparian buffers, also known as forested buffers, consist of natural vegetation on the edge of streams or along the shoreline of wetlands. The area, known as the riparian zone, protects and separates the stream, lake, or wetland from human as well as natural interferences.
Among the many benefits that these buffers provide, they are known to trap pollutants from runoff and reduce the amount of sediment entering streams, improving water quality. Herbaceous and woody tree roots allow sediment to settle out and prevent soil erosion. Food as organic material and woody debris as habitat are provided for invertebrates, fishes, and wildlife. The water temperature is also controlled by the amount of sunlight reaching the stream through the trees, meaning riparian buffers help keep streams cool during the summer. The impact of flooding is also reduced by riparian zones that store the water. The wider the buffer, the greater the benefits.
Anthropogenic degradation of riparian zones like residential developments or roads has greatly impacted the important physical, biological, ecological functions that those buffers provide. The USDA Forest Service estimates that over one-third of the rivers and streams in Pennsylvania have had their riparian buffers degraded or altered (DEP, 2006). From our own observations over the years at the Clean Water Institute, we have noticed drastic changes in the stream water quality in streams whose riparian zones have been altered. Some streams near agricultural areas in Lycoming County have recently been stripped of their riparian zones, which has greatly increased the number of E.coli bacteria in the water through animal wastes that get washed away in the water with no barrier to trap it.
Grafius Run, one of the urban streams that our team has been monitoring, shows signs of drastic impacts due to the lack of riparian buffers. The stream has been mostly drying the last few summers we have been monitoring it. In addition, a lack of riparian shading makes it difficult for a thriving aquatic environment to develop.
A study by the Chesapeake Bay Foundation of 16 streams in eastern Pennsylvania found that forested streams were more efficient at removing pollutants from water than non-forested streams. In the case of nitrogen pollution, 200-800 times more nitrogen reached the stream in the non-forested segments than reached the stream in the forested segments.
To preserve the water quality of our streams, it is imperative for people to understand the benefits of riparian zones and to spread awareness about it. Municipalities are allowed by Pennsylvania law to adopt land use regulations that protect riparian buffers and maintain the quality of the streams. Through inclusive civic engagement, any concern about a damaged riparian zone must be reported to the municipality for overview and native grasses, shrubs and trees can be replanted to protect the waters.
By Matthias Noble, Clean Water Institute Intern, Summer 2022
As stated on city of Williamsport.org in their article “Only Rain Down the Drain” swimming pools in the municipality are prohibited to be drained into the street or down a storm drain. Rather, it is suggested that the pool is left untreated with chlorine or any other chemicals over the span of two weeks. Afterward, the pool can be drained into the sanitary sewer system, if given permission by your local wastewater authority, or it can be drained into your property at a maximum of 12 gallons per minute. If you do decide to drain your pool gradually onto your property, be sure that no water runs off your property, into the street, or into a nearby stream.
Above: A Sanitary Sewer Access Point
Why care about what goes down storm drain?
By Joel Noble, Clean Water Institute Intern, Summer 2021
The containers we use for our refuse all have the potential to be environmentally harmful when not used and maintained properly. Water that enters a trash can or dumpster and mixes with its contents is deemed “leachate” which is prohibited from entering waters owned by the state (i.e., every body of flowing water whether it is a stream in pristine condition or your nearest storm drain).
You can help limit damage to public water and wildlife by ensuring that your waste containers are in a covered area that does not accumulate rainfall and by ensuring that your container’s lid fits tightly and is free of any leaks or holes. Additionally, make sure you know the proper disposal methods for the things you throw away: chemicals in the form of batteries, paint, detergents, motor oil, and other home chemicals should not be disposed of with your general refuse. It only takes a small amount of leachate with harsh chemical contaminants to make a serious negative impact on your local water quality. Even if you are not in an area with many impervious surfaces or storm water management systems, proper disposal of waste is important to the environment and your immediate living space. Leachate in an environment with little to stop it from soaking into the earth can easily end up in groundwater. Groundwater in more rural areas is often your primary water source for all things in your home through a well on your property. Your actions towards water management in how you store and maintain your refuse container can go a long way in limiting negative impacts to your local water and wildlife.
By Nathan Wolff, Clean Water Institute Intern, Summer 2021
Every winter, the northeastern US sees many episodes of wintery mixes and heavy snowfalls. To keep people on the roads and traveling safely, state Departments of Transportation work around the clock plowing and salting snow and ice. Unfortunately, keeping the roads safe and clear comes with some negative impacts on the environment. In the entire U.S., 37% of drainage areas have experienced increased salinization in the past five decades (Bennett, 2021). Here in Pennsylvania, PennDot has nearly 40,000 miles of roads and almost 96,000 snow-lane miles to maintain. Over the past five winters, they have used an average of 807,766 tons of rock salt on our roads (PennDot, 2022). Although methods of deicing the roads reduce vehicular accidents by 78-87%, we should still concern ourselves with the damage it does to our environment, particularly when salt is used in excess (Hintz et. al., 2021).
Road salts can contaminate drinking water, cause property damage, and harm wildlife (EPA, 2020). When salt finds its way into sources of drinking water the increased salinity can lead to human health risks like high blood pressure and future cardiac issues. Numerous case studies demonstrate contaminated drinking water exceeding thresholds for human salt consumption (EPA, 2020).
Contrary to popular belief, most modern drinking water plants are not equipped to fully remove all chemical contaminants, including excess salts. The main way these drinking water plants remove salts and other contaminants is by reverse osmosis (RO) (Magnus, 2021). RO filtration is very effective, but there are also many practical disadvantages that come with it. Reverse osmosis systems are expensive, they require costly professional maintenance, there are risks bacterial growth due to chlorine removal, and it can waste as much as six times the amount of clean water produced (Magnus, 2021). Most drinking water plants can’t afford to have big and efficient filtration systems, they are often simple and can lack in some areas of filtration, such as desalination. They are never 100% effective so not all salts are removed before we take a drink. Exceedingly high levels of salt can also damage peoples’ vehicles from its corrosive effects: according to AAA, rust caused by winter road salts costs Americans three billion dollars every year (Edmonds, 2017).
The smallest fractions of dissolved road salts can take months to years to travel from roads to nearby streams (Snodgrass et. al., 2017). Northeast stream studies consistently show increasing trends in salt concentration during both summer and winter months (Snodgrass et. al., 2017). Other studies indicate that not all road salt applied in a particular winter season is exported from watersheds within the same year (Snodgrass et. al, 2017). This means every year when roads salts are applied, they accumulate on top of what remains in surrounding lawns, pavements, and sidewalks from the previous year. Considering the amount of rock salt used in the US has tripled since the 1970s, the salt concentration in our environment must be unfathomable (Hintz et al., 2021). We should all be concerned about this and what it means for the ecosystems and wildlife that suffer because of it.
The most common deicing salts are inorganic chlorides with metals such as sodium, calcium, potassium, and magnesium (Hintz et. al, 2021). These salts do not just disappear after the snow and ice is gone. They are washed away as runoff, leaving behind concentrated residues, or ending up in a nearby water source. This harms both the biggest and the smallest wildlife around. Salt residues attract deer species to roadsides as they enjoy licking the salt and increases the probability of vehicle collisions (EPA, 2020). Salinized runoff also results in plumes of contaminated groundwater that adds salt ions to streams year-round (Snodgrass et. al, 2017). At high concentrations, salt can be fatal to zooplankton and macroinvertebrates, which serve as a critical food resource to many fish species. Salinity has been found to negatively affect the abundance of zooplankton in general (Yuan et. al, 2020). Chloride ions are lethal to macroinvertebrates because they compromise important osmoregulatory processes (Fink 2021). Adult fish can build tolerance to periods of increasing salt concentrations, but sub-lethal effects lead to egg mortality (Summers and Valleau, 2022). Fishermen should be alarmed because egg mortality and lack of food decreases total fish abundance. If they can’t survive at birth or eat as growing adults, they will die. Salt also has negative impacts on abiotic components of stream ecosystems such as water mixing. This can lead to salty dead zones down near the streambed (Summers and Valleau, 2022).
Current salt thresholds for the environment are set by the Environmental Protection Agency (EPA). The goal of these standards is to limit how much salt is used to begin with. There are both chronic and acute salt thresholds. Chronic thresholds are for reducing accumulating salt effects that keep getting worse over time, while acute thresholds are used to reduce the amount of salt that gets applied to the roads each year (Hintz et. al, 2021). Unfortunately, our streams are approaching these thresholds at alarming rates. A study by Kaushal et al. (2005) found that 55% of the urban streams they sampled had chloride concentrations 20-30 times higher than the EPA’s chronic thresholds. Contaminated streams can maintain high salt concentrations throughout the summer months, which heavily contributes to these alarming concentrations (Hintz et. al, 2021). The bottom line is that current thresholds are clearly not enough to reduce this environmental problem. Perhaps we can move in a direction towards new technology to help reduce the amount of salt used on our roads in the winter.
One promising solution to our road salt problem may be porous pavement to reduce the amount of salt used on impervious surfaces like typical roads, driveways, sidewalks, and parking lots. Instead of water pooling on the surface and going through freeze-thaw periods, it can soak into the ground naturally. There would be no need to salt these areas anymore because there would be no residual ice patches. A recent study has shown that annual median snow/ice accumulation on porous pavement led to a 77% reduction in annual salt used for maintenance (EPA, 2020). As homeowners, we have the responsibility of taking care of not only our property but the natural ecosystem around it. Instead of carelessly dumping rock salt on our driveways and sidewalks, we should severely reduce how much we use and look to other ways of dealing with ice. An easy way to reduce the amount of salt we use is to clean up snow and sleet as soon as possible, instead of letting it freeze and turn into an icy mess. At that point there is no option but to get chopping and salting. A cool alternative deicer is grape skin compounds. Researchers at Washington State University extracted chemicals from grape skins and made a solution out of it. Their solution melted ice quickly and effectively, all without damaging roads or harming the watershed (Bennett, 2021). This method is great because it turns waste products into environmental solutions. In general, we should continue to practice reducing salt usage on our properties and implement new deicing technologies to address environmental concerns like salination of freshwater sources.
Bennett, Paige. 2021. 8 Sustainable Alternatives to Sidewalk and Road Salts. https://www.ecowatch.com/sustainable-alternatives-winter-salts-2656111075.html
Edmonds, Ellen. 2017. Road De-Icers Cause $3 Billion Annually in Vehicle Rust Damage. AAANewsRoom. https://newsroom.aaa.com/2017/02/road-de-icers-cause-3-billion-annually-vehicle-rust-damage/
Fink, Kendra. Effects of Salt Runoff on Aquatic Macroinvertebrate Colonies. Masters Program-Bemidji State University. 2021. https://www.bemidjistate.edu/directory/wp-content/uploads/sites/16/2021/05/2021.-Fink-K.-Effects-of-salt-runoff-on-aquatic-macroinvertebrate-colonies.pdf
Garrido, S., Ben-Hamadou, R., Santos, A. et al. Born small, die young: Intrinsic, size-selective mortality in marine larval fish. Sci Rep 5, 17065 (2015). https://www.nature.com/articles/srep17065#citeas
Magnus, Jern. 2021. What are the pros and cons of Reverse Osmosis water filters? https://tappwater.co/en/reverse-osmosis-ro-water-filters/
Snodgrass, W. Joel, Joel Moore, Steven M. Lev, Ryan E. Casey, David R. Ownby, Robert F. Flora, and Grant Izzo. Influence of Modern Stormwater Management Practices on Transport of Road Salt to Surface Waters. 2017. Environ. Sci. Technol. 51. 4165-4172. https://pubs.acs.org/doi/abs/10.1021/acs.est.6b03107
Hintz, D. William, Laura Fay, and Rick A. Relyea. Road salts, human safety, and the rising salinity of our fresh waters. Front Ecol Environ. 20 (1). 22-30. https://esajournals.onlinelibrary.wiley.com/doi/10.1002/fee.2433
Kaushal S.S, Groffman P.M., and Likens G.E. 2005. Increased salinization of fresh water in the northeastern United States. P Natl Acad. Sci USA. 102: 13517–20. https://pubmed.ncbi.nlm.nih.gov/16157871/
Summers, Jamie and Robin Valleau. 2022. Road salt is bad for the environment, so why do we keep using it? Queen’s Alumni Review: The Magazine of Queen’s University. https://www.queensu.ca/gazette/alumnireview/stories/road-salt-bad-environment-so-why-do-we-keep-using-it
United States Environmental Protection Agency. Winter is Coming! And with it, tons of salt on our roads. 2020. https://www.epa.gov/snep/winter-coming-and-it-tons-salt-our-roads#:~:text=In%20addition%2C%20road%20salt%20can,fish%2C%20bugs%2C%20and%20amphibians
By Elisa Dallo, Clean Water Institute Intern, Summer 2022
Stormwater is water from the rain or snowstorm that rushes over impermeable
surfaces like pavements, parking lots, and roofs. Stormwater systems are specifically
termed as Municipal Separate Storm Sewer Systems or otherwise known as MS4. The
“separate” term is due to the system not being part of the sanitary sewer system where
wastes from drains like toilets are destined for treatment plants for filtration. To reduce
flooding, storm drains are established so stormwater is diverted off of paved surfaces
and into watersheds like streams, creeks, and rivers. As more landscapes–like parking
lots, sidewalks, and streets–develop, more stormwater gets sent directly to watersheds.
This elicits a reasonable call of concern as many pollutants flow with stormwaters and
eventually destroy aquatic life when they reach streams.
Surprisingly, a good example of a not-so-obvious contaminant is pharmaceutical
drugs. We may not realize it as we dump used needles on pavements or flush unused
medications down the toilet. Even if the sanitary sewer system is separate from MS4,
drugs can go through sewage-treatment plants undetected and reach the MS4 instead.
As a result, drugs can act as contaminants and end up in waterways. Although the
concentration of pharmaceutical compounds is lower in rivers than the usually
prescribed dose and therefore hardly affects human health, the compounds can
drastically affect aquatic wildlife like fish. Some pharmaceutical drugs contain endocrine
disruptors which alter internal biological processes like hormone regulation. Endocrine
disruptors are usually estrogen found in birth control pills. One study observed that
fish–bass–in the Potomac River are found to be especially vulnerable to these
disruptors as they underwent secondary sexual characteristic changes. Therefore, it
could lead to reproductive failure and population decline. The study is yet to account for
key mutations that cause the intersex phenomenon, but the trends suggested
endocrine-disrupting compounds are responsible. Whether drug compounds affect
aquatic wildlife more than human health remains a serious concern and worthy of
research. It is important to conduct further studies in relation to stormwaters,
mismanaged trash, and proper disposal of medications in order to generate more
aggressive long-term solutions and regulations such as upgrading treatment
infrastructure–which is especially important when considering that most treatment plants
are not currently designed to filter drug compounds in water.
Some of the ways to reduce pharmaceutical waste are already in place. One of
the most obvious examples is to be educated about proper disposal and practice it by
not dumping unused/used medications on pavements and into storm drains. The same
goes with flushing drugs down the toilet. Instead, participate in drug take-back programs
where consumers like us have a safe way to properly and legally dispose of unused
drugs to the right authorities. Another simple solution is to limit bulk purchases to
minimize pharmaceutical footprints in the water. Environmental groups are already
appealing to drug manufacturers to design environment-friendly drugs where
compounds break down upon excretion or are thoroughly metabolized by the body.
A good example of eco-friendly drugs is the ones that react through
“organocatalysis”. Catalysts are molecules or substances that increase the rate of
reactions. Usually, metals are used for catalyzing reactions but metal catalysts are
expensive, rare, and harmful to the environment. Thanks to Nobel Prize winners David
MacMillan and Benjamin List for the development of asymmetric organocatalysis, we
are now able to use organic carbon-based catalysts that are easily handled in
large-scale reactions. In addition, this discovery prevents the use of large amounts of
solvents and can therefore minimize waste. The term “asymmetric” comes from the fact
that only one analog of the two mirror images of the molecule exists. Organic molecules
exhibit a special characteristic called chirality. When the two molecules face each other,
they are a mirror of each other but when laid on top of the other, they do not match. This
pair of molecules is always produced during certain reactions. For example, the
s-limonene is the molecule responsible for the lemon scent whereas its analog,
r-limonene is responsible for the orange scent. A left-handed molecule can only be
pharmaceutically useful but its right-handed partner could cause health issues.
Asymmetric organocatalysis is very efficient as it only produces the desired analog.
Now that there are many ways and simple innovations in place to help minimize
pollution in watersheds, we still have a long way to go. Further research is necessary to
assess whether pharmaceuticals in streams have adverse effects on human health.
More efforts on source control are needed as well in order to strengthen long-term
solutions. But while we are waiting for more long-term solutions, it is no doubt helpful
that we continue to practice basic measures that reduce pharmaceutical pollution in our
By Daisy LeBlanc, Clean Water Institute Intern, Summer 2022
What is Permeable Pavement?
Permeable pavement is a mitigative stormwater management strategy that allows water to pass through the surface of the pavement into a stone reservoir before infiltrating into the ground. Permeable pavement prevents stormwater generation, allows stormwater to infiltrate the ground once it’s created, and removes pollutants from stormwater. As a result, permeable pavements reduce contamination from and in stormwater runoff by reducing the stormwater and pollutant concentrations going into storm drains. This also resupplies the groundwater while circulating water and air into plants’ root systems. They also lead to less salt on the roads, another ecological benefit, because they cause snow and ice to melt faster.
Pervious pavement is designed with three layers for water to move through. First, water meets a layer of permeable surface and drains into the underlying second layer of uniformly graded stone bed which provides temporary storage and promotes infiltration. The water then slowly drains into the third layer of uncompacted soil, which acts as an infiltration bed. This bed is top-lined with geotextile fabric to separate it from the stone bed. From here, water can return to groundwater supplies.
Types of Permeable Pavement
There are a few different types of permeable pavements. The first are porous asphalt and pervious concrete, which both are similar to traditional pavement, but have a reduced sand concentration to create better porosity. These pavements have better traction than traditional asphalt or concrete. Next, Permeable Interlocking Concrete Pavement (PICP) utilizes spaces in the concrete to allow water to infiltrate to the ground.
Homeowners can achieve meaningful environmental benefits by installing pervious structures to areas that otherwise do not allow for drainage (driveways, parking areas, walkways). This can be done by installing impervious materials like asphalt, concrete, or brick with gaps between for pervious materials like gravel, sand, and vegetation. Traditional gravel driveways, though, do no qualify as permutable pavement because they do not allow for infIltration, creating storm water runoff.
Permeable pavement, while more expensive to install, can be very cost effective in relation to traditional pavement. The savings in maintenance and stormwater management costs make up for higher per foot construction. For example, in Pennsylvania, permeable pavement costs about seven dollars per square foot to install, whereas asphalt alone costs about two dollars per square foot. But when considering the full construction costs including stormwater management, typical asphalt construction comes to more that fifteen dollars per square foot. The exact cost of installation depends on site conditions as well as the level of stormwater management needed.
Some limitations of permeable pavement reduce the spaces appropriate for installation. For example, permeable pavement is not as strong as traditional asphalt, so it is not recommended for areas with high volumes of traffic or heavy loads like highways and busy roads. Moreover, permeable pavement is not for “stormwater hot spots” with hazardous material, whether it is being loaded or unloaded, stored, or if there could be spills or leaks.
Permeable pavement can be used by businesses, government spaces, and homeowners to reduce the amount of storm water runoff. Before installing a permeable pavement, one must consider the type, area, and cost. While permeable pavement Is not suited for every location, it can be a cost-effective way to contribute to clean water practices.
Bureau of Watershed Management, “Pennsylvania Stormwater Best Management Practices Manual,” Department of Environmental Protection, 2022, http://www.stormwaterpa.org/bmp-manual-introduction.html
County Conservation District, “Using Smart Growth Techniques as Stormwater Best Management Practices,” United States Environmental Protection Agency, 2022, https://lancasterconservation.org/~lancatd6/wp-content/uploads/Stormwater-BMPs-smart-techniques-1.pdf.
National Pollutant Discharge Elimination System, “Permeable Pavement,” United States Environmental Protection Agency, 2022, https://www.epa.gov/system/files/documents/2021-11/bmp-permeable-pavements.pdf#:~:text=Description%20Permeable%20pavements%20are%20a%20stormwater%20control%20that,pervious%20concrete%20and%20permeable%20interlocking%20concrete%20pavement%20%28PICP%29
State Transportation Innovation Council, ”Pervious Pavement,” Pennsylvania Department of Transportation, 2022, https://www.penndot.pa.gov/about-us/StateTransportationInnovationCouncil/Innovations/Pages/Pervious-Pavement.aspx