Sediment Limits: Not Always by the Numbers

A draft of EPA’s new stormwater rule is scheduled to be released in June 2013, with finalization (after the public comment period) projected for December 2014. The rule, initially scheduled for implementation in November 2012, is expected to include such provisions as integrating green infrastructure into project design; viewing stormwater as a resource; and generally slowing the flow of runoff to allow more infiltration, which will not only reduce the volume of runoff but also the amount of pollutants reaching receiving waters.

For several years, EPA had also been considering numeric turbidity limits for construction-site runoff. However, the agency suspended its efforts and when it released its new national Construction General Permit in February 2012, the CGP did not include a numeric limit. EPA stated at the time that even if it established a numeric limit within the next five years-the term of the current CGP-it would not modify the CGP to include the limit but would instead incorporate it into the next iteration.

In the absence of any federal limits, some states have implemented limits of their own-whether to anticipate future federal limits, or to protect their drinking and recreation waters, or both.

Michigan: a State and a Lake
Television commercials for the state’s tourism use the tagline “Pure Michigan.” Most of the ads include shots of sparkling blue waters.

Michigan’s Department of Environmental Quality (DEQ) is responsible for keeping the state’s waters clean, and it achieves this goal through a “narrative” turbidity standard, not one with a numeric limit. Michigan’s DEQ refers to these as “Part 4 Rules-Water Quality Standards,” under Part 31, Water Resources Protection, of the Natural Resources Environmental Protection Act (NREPA):

R 323.1050 Physical characteristics. Rule 50.

The surface waters of the state shall not have any of the following physical properties in unnatural quantities that are or may become injurious to any designated use:

• Turbidity
• Color
• Oil films
• Floating solids
• Foams
• Settleable solids
• Suspended solids
• Deposits

“DEQ staff evaluate these standards on a site-by-site basis, and determine how we will respond, based on characteristics of the discharge and the receiving water,” explains Sarah VanDelfzijl, soil erosion and construction stormwater program specialist. “I think the challenge with all regulations is that ultimately people want flexible certainty. They want a fixed compliance point that they can have as a target and be certain they are in compliance, but they also want the flexibility to deal with their unique situation in different ways than what that fixed compliance point might allow. That’s really tough to achieve. I think what we’re doing works, and it allows us to build upon local regulation of soil erosion, which we already had in Michigan.”

She continues, “Michigan established an erosion control law [Part 91, Soil Erosion and Sedimentation Control] in the 1970s, creating soil erosion enforcing agencies at the county level, and allowing municipalities to opt into running a SESC permitting program. Part 91 requires any earth change within 500 feet of a lake or stream, or a site greater than one acre, regardless of risk for a discharge, to get a soil erosion permit. The DEQ requires a certified stormwater operator for sites of an acre or more. The certified operator evaluates the site and the SESC measures weekly, and within 24 hours of a rain event.”

Both Part 91 and Michigan’s “permit by rule” policy, which implements the federal construction stormwater program, requires that the permittee establish a plan. “We don’t specify BMPs that must be in the plan; we just require that sediment is removed from runoff water before it leaves the site. This is even more restrictive. Counties regulate stormwater runoff so that no discharge is occurring. The DEQ stormwater program builds from the local program with additional requirements, and can partner in oversight and compliance activities. Part 91 has other generic plan requirements, such as including soils, slope, limits of earth change, and so on that must be included in a site’s plan.”

Plans are reviewed at county and municipal level by the Part 91 soil erosion control agencies to ensure that permittees are effectively planning, implementing, and maintaining measures in conformance with Part 91. “The Part 91 agency also independently inspects earth changes to ensure the site is complying with its permit and plan,” VanDelfzijl says. “When the earth changes get big enough-over one acre with a point source discharge to waters of the state-Michigan’s permit-by-rule comes into play. Permit-by-rule implements the federal construction stormwater programs. Sites that meet these size thresholds then must have a certified stormwater operator inspect the site weekly and within 24 hours of a rain event that results in a discharge from the site. DEQ staff also spot-checks sites to ensure compliance with Part 91 and Michigan’s permit-by-rule.”

Michigan’s DEQ has nine regional offices, with one Part 91 agency for each county; a large number of municipalities elect to run Part 91 programs of their own. “Michigan’s geography varies, as does its local economies; therefore permit volumes vary from county to county and region to region. Any given numeric turbidity standard may be right for a particular stream, but not quite right for a stream of a different size. Plus, after a rain event, streams will have a natural turbidity. The narrative standard allows us to evaluate discharges on site-by-site and stream-by-stream basis.”

Will Michigan standards change if EPA announces a turbidity limit? “We’re watching what the EPA does, and will evaluate then, if we have to change something when it decides,” she says.

Waterways that border two states, or rivers that wander out, and back into, a state, requires interstate cooperation. “A prime example is the St. Joseph River, which flows down into Indiana, then returns to Michigan,” notes VanDelfzijl. “If any discharge originates from Michigan, we cover it. If it comes from Indiana, they cover it. We work cooperatively with them to solve issues. A good example of this cooperation is the St. Joseph River Watershed Planning Project.” (More information on this project is available at http://www.fotsjr.org.)

Florida: Sun, Surf, Sand, and Clay
Say “Florida,” and most people think of its coastline’s beautiful sandy beaches. The state’s soils vary, however. Silty muck is found in swamp areas, and the panhandle contains clay soils. All these conditions must be taken into account when establishing turbidity levels. Eric Livingston, program administrator for MS4 permits for Florida’s Department of Environmental Protection, NPDES Stormwater Section, explains.

“Florida’s had water protection rules in place since 1982,” he says. “As every program, we’re technology based, with three cornerstones of these programs: performance standards, design criteria for BMPs for those goals, and the task of constantly improving those criteria.”

The state water implementation rule, 62-40 of Florida Administrative Code, contains the performance standards for Florida’s program. “For erosion control, one must retain property on one’s own site, and discharges cannot exceed 29 NTU [nephelometric turbidity units] over background.”

Livingston’s office doesn’t perform monitoring. “If we can see turbidity, it’s a violation. However, in the southern part of the state, you seldom see it, due to the sandy soils, which filter it out. With its clay soils, northern Florida has more of a problem with turbidity. Mostly, taking care of this problem is basic common sense. You have to get an environmental resource permit that integrates erosion control and stormwater control during and after construction for virtually any project. You have to lay out what you’re going to do during construction, and first thing, a stormwater system must go in. If we go out and inspect and see turbidity, that’s a violation, which we determine by grabbing samples up- and downstream of a specific site.”

Most of Florida is flat and sandy, with hilly conditions and clay soils in the panhandle. In addition to being surrounded by the Atlantic Ocean and the Gulf of Mexico, the state contains more than 8,000 lakes and 29 major estuaries.

“The “˜29 NTU over background’ rule varies, because the background varies,” Livingston explains. “As I mentioned, sandy soils clean up; clay soils are more of a problem. If a river has mud base, it has lots of natural turbidity. Many waters are highly colored, due to tannins in the water that drains from wetlands-so the limits have to be variable. Especially in clay soil areas, we’ve been using some coagulants for many years, mainly PAM, which has to be tailored to the soil at the site. It’s safe to say that in clay soils, chemical treatment will probably be needed.”

Florida isn’t waiting for EPA to establish a numeric limit. “The EPA has been talking about this for years and hasn’t settled on guidelines,” he concludes. “In conjunction with Florida’s DOT and the University of Central Florida, we recently updated our state erosion and sediment control BMPs in the Florida Designer and Reviewer Manual, which includes the latest, greatest BMPs. When we want to test some BMPs, we can always use the world’s best rainfall simulator at the University of Central Florida.”

California: Taking a Step Back
A few years ago, California issued turbidity limits, but they didn’t last long. “We made turbidity limits in 2009 in our reissued statewide construction general permit,” says Greg Gearheart, P.E., senior water resource control engineer for California’s Water Boards, Division of Water Quality, Storm Water Program-Industrial and Construction. “That 2009 version of California’s CGP contained numerical effluent limits, or NELs, on high-risk sites (or Risk Level and Type 3): pH less than 6; pH greater than 11; and 500 NTU. However, those limits and lots of other permit issues were challenged by the building industry in court. In December 2011, the court agreed on removing the NELs. We had a choice to either redo our rationale or remove the NELs; we removed the pH and turbidity limits in July 2012.”

But that might not be the end of the story: “Now environmentalists are challenging the decision to remove the NELs,” he notes.

Gearheart and the State Water Resource Control Board oversee such issues for the entire state, and the turbidity issue isn’t quite dead yet. “One other sort of de facto limit: Water-quality standards still have to be met. California has nine different water-quality board regions, which all have turbidity standards-which could be applied at the point effluent discharges-contained in their basin plans.”

Although he says it’s unlikely that small localities, through an ordinance, have turbidity limits in place, Gearheart points out the exception: “San Diego has lower levels instream; for example, 20 NTU for all inland surface waters.” He notes that construction permits don’t establish that level, but the permits do enforce it, along with all other basin plan standards and prohibitions. “The limit is not just for construction sites; it applies to possible types of discharges, like agricultural and industrial.”

He adds, “Nationally, all NDPES permits for construction-site stormwater contain both effluent limitations, which could be narrative or numeric limits, and a requirement to not cause or contribute to an exceedance of water-quality standards. Other basin plans say “˜turbidity can’t be more than X% above background’-so one has to know what local streams carry in the background.”

In California, which contains clay soils throughout the state, background estimates can be fairly easily determined. “You can somewhat estimate what turbidity will be from the 1950s soil conservation guidelines and the uniform soil loss equation, or the revised USLE, RUSLE. Key factors are length of slope, how much and what type of soil you lose, and rainfall intensity.”

Maryland: Controlling but not Counting
Maryland’s Department of the Environment recently rewrote standards for sediment control, construction permits, and NPDES, but turbidity limits weren’t included.

“We didn’t put a numeric limit for sediment,” says program manager Brian Clevenger. “We’re not going to do it until EPA moves on this issue. Just about everything from Maryland drains to the bay, so our sediment control program was founded in 1970 and has been focused on minimizing deposition off construction sites. Requirements for new development must meet our specs for runoff control; anything over 5,000 square feet must have a sediment control program submitted and approved.”

Clevenger’s office inspects state and federal construction projects; local entities handle their own enforcement. “In the early 1980s, the laws were changed to make us responsible for these plans. But if a local entity wanted to enforce, it could be delegated the authority, so long as there’s consistent inspection during the construction.”

He outlines the procedure: “When an inspector finds problems on a site, a report is written: “˜You have to fix this by such a date.’ If the inspector finds the practices put in are not doing the job, he’ll tell the permit holder, “˜What you’re doing’s not enough; get an engineer in here to fix this.'”

Although everything south and east of the I-95 corridor is mostly coastal and sandy, clay soils abound in the state, and that’s “almost impossible to get out,” he notes. “Often, a PAM treatment will be used to take care of the microparticles in watered clay. Our office has discussed the turbidity issue, suggesting polyacrylamides be used, but care must be taken. If you use the wrong PAM, the runoff will kill fish, and if the user doses the stream or basin too heavily, it can kill downstream. But the chemical is effective.

I’ve seen sites use a cleaning method in which they’ll hang a brick of PAM in a 55-gallon drum, using it for a filter for runoff. There’s a discernable difference in what went in and what came out. Of course, you’re never going to get “˜drinking water’ off a construction site, but you must minimize damage downstream.”

What the future holds is uncertain. “USEPA had been throwing around ridiculously low limits that even nature couldn’t meet,” Clevenger says.

“We’re not unsympathetic to either view-the environmentalists and the construction business-but reasonable standards must be set. We don’t get that much rain; 90% of our rainfall events are one inch or less, and sediment basins are based on that 1-inch storm. Of course, then, something like Hurricane Sandy comes by and dumps about a foot of rain on the state-then you have problems. After big storms, we get complaints about sediment off construction sites.”

A Maryland “Do-Over”
During the construction of a Super Wal-Mart in Denton, MD, Sterling, VA’s RIV Construction Group ran into a problem with runoff. Influent storm water contained 700 to 900 NTU, and the controls RIV had put in place failed to clean it up.

“One problem-the groundwater levels were high, about 3 feet below the surface,” says RIV Superintendent John Raum Jr. “Due to this, we had to over-excavate the site and put in stone. Also, right behind the site, there’s a retention pond for sewerage treatment plant, which is about 10 feet higher than the Wal-Mart site. Add to this the very sandy and some clay soil, and Denton sited about an hour from the ocean and Chesapeake Bay, and water was quite a problem.

“Our project, run in conjunction with Elite Construction, began in November 2011. A retention pond and system went in for the construction period. The pond was there to catch any rainwater before it left the system. Our original plan had an outfall; gravity should’ve made the sediment fall, but it wasn’t working that way. As this pond was supposed to drain into a nearby creek, we had to block it off until we didn’t have any sediment in the discharge. While working on a better solution, we blocked it off with a rubber ball in the pipe and a piece of plywood staked against the opening. At that point, it was mid-January, and the spring rains were right around the corner.”