Preserving Water Quality

Until fairly recently, residents of southern coastal South Carolina took for granted the abundance of blue crabs, shrimp and numerous sport fish that occur in local rivers and salt marshes. Today, however, these waters are showing signs of stress that have been created by development. The question now has become: “Are we destined to lose our seafood and sportsfishing like all the other coastal communities have experienced rapid density development?”

The answer is “not necessarily - there is still a slowly closing window of opportunity to keep what we have.” The LowCountry Institute is working with staff of municipalities and county governments, as well as with local residents and developers, to understand how development degrades water quality and possible solutions that new scientific information is providing. A critical part of this process is making sure that everyone is asking the right questions. This includes understanding how our region is similar - and different - from other coastal regions that have been studied.

Four Key Questions:

1) Who is responsible for passing laws that protect local water quality?

If Beaufort County and local municipalities rely on state or federal laws for protection, they will lose most of their oyster beds and quality seafood nursery areas. An important lesson learned from decades of work trying to improve water quality in the Chesapeake Bay is that once you lose your water quality, you can never return it to its original state.

Current state and federal regulations are designed to keep the waterways from becoming more polluted, but the standards in coastal South Carolina are based on water conditions that already exist in developed areas, such as Myrtle Beach and Charleston. Since water quality in these areas had already been degraded, the state legislature will not approve standards that would require counties to clean their water to pre-development levels. Similarly, the Environmental Protection Agency provides funding to clean up polluted (impaired) waters, but not to protect waters that have not yet been polluted, even though this is obviously more cost effective.

A study by the S.C. Sea Grant Consortium showed that only local governments have the ability to protect local water quality because zoning stormwater ordinances provide the greatest protection for local waterways. Thus, protecting the water quality of Port Royal Sound and its tributaries is the responsibility of Beaufort County and Jasper County and their municipalities.

2) How does stormwater runoff from developments damage water quality?

Natural, undeveloped landscapes and developed landscapes handle rainfall very differently. In nature, much of the precipitation never reaches nearby rivers and salt marshes because rainfall soaks into the ground and or taken up by trees and returned to the atmosphere (up to 70% in the summer). Rainfall that does reach the salt marsh does so by moving slowly through the soil, resulting in it reaching percolating into the marsh slowly over a period of days or weeks.

In contrast, rainfall falling on developed areas is called stormwater runoff because large volumes run off quickly into creeks and ponds due to large areas (roofs, parking lots and roads) being impervious to water. In a typical community approximately 65% of the impervious surface is associated with transportation, which includes parking lots and roads.

When water accumulates on impervious roofs and parking lots and large volumes run off into creeks and other waterways, the water washes pollutants with it and the rapid flow rates erode the banks of drainage ditches and the tidal creeks into which they flow. The pollutants associated with stormwater runoff thought to damage local waterways are (in decreasing order) excessive fluctations in fresh water, coliform bacteria, pesticides, nutrients and heavy metals.

3) How do these pollutants damage the environment?

A. Fresh water

The Port Royal Sound system is now probably the most productive area for seafood species in the United States. It is a high salinity embayment containing 50% of the state of South Carolina’s salt marsh. It has the largest unpolluted nursery areas for crab and shrimp larvae in the Southeast. These nursery areas are located in the blind-ending creeks and tributaries that branch off Port Royal Sound. The key to Port Royal Sound’s productivity is that it has very little freshwater runoff entering it. Human development can significantly alter this natural condition by channeling stormwater runoff from paved areas directly into a small saltwater creek. This causes dramatic changes in salinity in a short time which stresses small marine organisms, such as larval shrimp, crabs and fish, living in the creek. Continued mortality of the earliest stages of these desirable species will eventually result in dramatic reductions in numbers of adults present.

B. Coliform bacteria

Coliform bacteria are the type of bacteria that live in the intestines of mammals (including humans), waterfowl and even alligators. Fine straining devices that oysters and clams have also remove bacteria from the water. A conventional test by the health department is to check to see if oysters have coliform bacteria in them. If they do, the health department regulations assume that these bacteria came from human waste that entered the waterway. If coliform bacteria are present, the assumption is pathogens such as viruses might also be present in the oysters. Therefore, elevated counts of coliform bacteria in oyster beds results in the oyster bed being closed to protect human health.

During the past decade scientists have documented that coliform bacteria counts in water may be high due to coliform bacteria that originated from wildlife (raccoons and deer) or from pets. This is very evident where waste from people’s dogs is washed down storm water drains directly into a waterway. The level of threat created by coliform bacteria coming from non-human sources remains a topic of debate.

C. Pesticides

Insecticides are highly toxic to the larvae of crustaceans (e.g. crabs and shrimp) if they enter local waterways. Insecticides can be long-lasting (such as those used under houses to kill termites and on lawns to kill fire ants) or short-lived (such as those purchased at the store to kill lawn and garden pests). When used properly, long-lasting insecticides remain in the soil where they were initially applied and the short-lived insecticides break down before they are washed into the waterways. These “non-water soluble” pollutants are transported into local salt marshes when the sediments to which they bind are swept away by eroding streams of poorly managed stormwater .

The closer a home is to the water, the greater the likelihood that the termiticide placed under a house’s foundation will leach into the waterway and pose a serious threat to crab and shrimp larvae. Similarly, the closer a lawn is to the shoreline, the greater the likelihood that a summer rainstorm will wash a recent application of insecticide into the waterway.

Insecticides used for lawn care often pose a greater threat than do insecticides applied on golf courses. Homeowners and lawn care companies typically apply insecticides at greater concentrations than golf course superintendents and therefore are much less likely to check weather forecasts before applying. These two conditions significantly increase the likelihood that insecticides will be washed into adjacent waterways before they degrade.

D. Fertilizers

Fertilizer in a waterway can stimulate the growth of excessive algae. When the algae dies and sinks to the bottom, it decays, removing oxygen from the water and stressing other aquatic life, especially fish.

In the Port Royal Sound system the impact of fertilizer depends on the location. In the headwater areas, fertilizers are a serious pollutant because there is no flushing. The same water moves back and forth up into these blind headwater areas. In areas adjacent to main waterways, the sound’s large tidal amplitude dilutes fertilizer and will have less effect.

E. Heavy Metals

Metals such as mercury, lead and arsenic are serious pollutants because they never decompose, they are toxic at very low doses, and they are fat soluble and therefore they accumulate in a person’s body throughout their life. Fortunately, most sources of these metals have been taken off the market.

4) What can be done to prevent stormwater from polluting local waterways?

A. Design new developments so that stormwater retained onsite.

1. Minimize the amount of impervious surface (pavement and roofs) that exists on the site. This gives more opportunity for water to percolate into the soil.
2. When possible avoid curb and guttering that channel large volumes of water offsite. A system of swales leading to a natural isolated wetland is an alternative to curb and guttering.
3. Plant young trees along areas with swales to increase water transfer directly to the atmosphere via tree “evapotranspiration.”
4. Send stormwater into shallow stormwater detention wetlands that can be managed as vegetated wetlands. These dry out during extended dry periods, and therefore can be mowed so that the vegetation is kept in a grassy, early successional state.
5. Maintain retention ponds which remove bacteria and some nutrients from the water.
6. High density developments (= “new urbanism”) should only be built on sandy, non-hydric soils that have high infiltration capacity.

B. Maintain vegetative buffers along the edges of waterways.

During heavy rain events a significant percent of stormwater runoff moves across the ground surface as “sheet flow.” This surface level runoff carries sediment and pollutants with it. A dense vegetative buffer of tall grasses acts as a filter to slow down sheet flow thereby trapping sediments. Maintaining an effective buffer along a shoreline requires keeping lawns away from the shoreline. The larger the uphill area creating the sheet flow, the wider the vegetative buffer should be. The most effective vegetative buffer consists of woody, deep-rooted plants bordered a swath of tall grassy and herbaceous plants, which is mowed annually in the spring.

C. Minimize the amount of insecticides and other organic pollutants (such as oil residues) present.

This is difficult when working with a residential community because so many different people are applying chemicals to their own property. This makes it almost impossible to control the quantity of insecticides being used unless they are taken off the market. Minimizing the amount of turf grass present reduces the need for insecticides. Having a well-educated community is essential to ensure that used oil and other toxic substances are disposed of onsite.

D. Restrict development density in areas with poorly drained soils.

Keep in mind that human development has occurred in this county for over 200 years. All suitable areas for development have already been used at least once in the past. Therefore, sites should show signs of previous inhabitation. Low-lying areas that have no evidence of past dwellings may indicate special problems associated with drainage, and projects in these areas should be scrutinized closely. The conventional practice of trucking in soil to elevate a site can create water quality problems if these are not sandy soils or are placed near the marsh. Initially, fill dirt does not contain the beneficial fungi and bacteria of natural soils, which absorb or break down fertilizers, pesticides and pet waste. Development of low-lying areas with saturated soils results in increased sheet flow across the surface of the ground. (Low-lying areas are characterized by clay soils which have low permeability.) Therefo requires wider vegetative buffers along shorelines and less onsite impervious surface area.

E. Require community associations to manage stormwater ponds and marsh edge buffers effectively.

Stormwater ponds should not be kept filled to capacity since this prevents them from being able to retain additional water from storm events. Ideally, marsh edge buffers in new developments should be owned by the community association which makes it easier for accountability of how they are managed.