### Review of URS Corporation Analysis of Two Documents Provided by North Carolina State University

By

Richard A. McLaughlin, Ph.D. Professor and Extension Specialist Department of Soil Science North Carolina State University
December 6, 20 10 Summary

The following is a review of a Section Seve n of the URS Corporation analysis of the development of the EPA Effluent Limit Guideline 1 . Section seven was an analysis of

three “true” Passive Treatment Systems ( PTS ) f or which information or data were available for use in the ELG calculation. The purpose of this review of that analysis is primarily to correct misinterpretations of data cited in this document which were from

two studies conducted by my group

. The misinterpretations revolved around what data

were include d or not and why. Where data are missing for certain dates in tables, it i s because the sampler failed to obtain a sample and no data were available , not because the PTS failed. The only data that w ere omitted was for samples collected during periods when the PTS was compromised or bypassed as a result of site activities , as observed upon sample collection soon after the storm event

. Data were omitted because they represented poor PTS m anagement, not the capabilities of PTS. To facilitate a review of these misinterpretations, t he relevant section (Seven) was pasted into this document and my comments, in italics , wer e inserted directly after the

erroneous section.

I do not have the data from th e third PTS cited (“Morrisville”) in the URS analysis

, however I did visit that site and saw at least some of the remnants of that attempt at turbidity reduction. In my opinion, the failure of the PTS was most likely due to i mproper inst allation . It appeared that solid flocculants were placed in open, rock

- lined ditches where they likely had uneven interaction with the runoff and were likely inactivated through exposure to the elements between s torm events. This may have been the typical “afterthought” approach to turbidity control, rather than integrating PTS into the overall stormwater management plan. It was not surprising that there was little or no turbidity reduction.

1 URS Corporation, “Discussion of the EPA Calculation and Implementation of a 280 NTU NEL Limit Based on Passive Treatment Technology for the Final C&D ELG,” March 2010 . Accessed

at http://newsletters.wetlandstudies.com/docUpload/PassiveTreatmentCD_ELG.pdf

.In addition, I have added a table of data from a 3 rd site that was very similar to the sites mentioned as “NCR.1” and NCR.2”, which correspond to Site 1 and Site 2 in the publi cation (McLaughlin et al., 2009), in Attachment 1 . This data is included to further illustrate the potential for su ccessful application of PTS. It was not included in the publication because we had few events in which samples were collected from all experimental sections of the site, due primarily to automatic sampler issues or low flow. I have included some very recent data as well from a site we are currently monitoring (Attachment 2).

With p roperly installed PTS, w e have had good success in reducing turbidity by 1

- 2 orders of magnitude in both controlled field testing and on active construction sites. When this does not occur there is almost always a problem with either the installation or maintenance of the PTS or activity that compromises the PTS.

### (The following is **copied from the URS document cited above)** 

VII.A The Data from the 3 True PTSs were I ntensively Screened and Edited by the Authors, yet EPA Undertook Further Editing of Very Limited

Data
Section Summary: The three true examples of PTS included in the limit calculations had very few data points, and were already heavily edited by the authors of the papers to only present the most favorable results. Nevertheless, EPA removed an additional point from

the NC

- RD site for no other reason than the result was higher than the only three other average results available. This removal was inappropriate, because it was a major proportion of the available data, and the authors could not cite a specific problem that would invalidate this data point. The three true PTS systems used by EPA in the NEL calculations were all installed as experiment al BMPs at road construction sites in North Carolina by Professor John McLaughlin and his associates from the University of North Carolina.

Correction: Professor Richard A. McLaughlin, North Carolina State University

URS believes that these BMPs are a useful improvement over standard BMPs on construction sites. Where URS has a disagreement with Dr. McLaughlin is as to whether these BMPs can consistently and reliably meet a legal compliance limit as low as 280 NTU under all conditions,

the violation of w hich can impose heavy civil, and possibly even criminal punishment.

W

e have demonstrated on numerous constru ction sites that a fully functioning PTS will drop turbidity by 1

- 2 orders of magnitude or more. My interpretation of the ELG is that there are exemptions, such as larger storm events with >2 year recurrence.

In comments to the proposal, Dr. McLaughlin joined with NRDC in endorsing a 200 NTU compliance limit for passive BMP controls, but he seemed to forget that in man y of his papers, the data was already highly edited to eliminate a very significant portion of the rain events tested, and only the most favorable results were reported. The papers explained that they eliminated reporting from rain events where the PTS BMP s failed because it was found not to have remained intact at the end of the rain event. But this does not adequately explain what caused the PTS to fail. If they were properly installed, but actually failed during the rain event because they

were overwhelm ed by the specific rain and site conditions, then the failure is an accurate portrayal of problems inherent with setting up PTS BMPs, and these data results should have been included if the data is to be used to evaluate a compliance limit.

This is an un fortunate misinterpre tation of the studies. Data were never “eliminated,” but either the sampler malfunctioned or there was insufficient flow to obtain a sample. This is clearly indicated in the table footnotes. The “failures” were not of the PTS but of the samplers.

In fact, records in the docket show that during rain events at the sites NC

- Rd1 and NC

- Rd2, McLaughlin and his associates, who were operating the systems, were not even at the site during the rain events, but were three hours drive away (Doc ket ID EPA

- HQ

- OW

- 2008

- 0465

- 2057). Not only were they not available to conduct real time interventions (which are not always practical to perform safely with true PTS systems), but they also did not have firsthandknowledge as to what occurred at the site t o cause PTS failure.

The reviewers do not seem to understand that the point of a PTS is that they are passive

– no intervention is supposed to be needed! While we were not often at the sites during storm events (although we were for some), we visited th e sites to collect samples soon after storm events and took pictures and noted what was occurring on the sites.

The three PTSs used by EPA already contained the following self

- edits to the data initiated by the authors:  For the NCR.1 site, the McLaughli n paper (Exhibit 10) eliminated five of the twentyseven rain events (18.5% of the original data) for which the Fiber Check Dam/PAM BMP was initially evaluated.


## SECTION 

# SEVEN

Page 42

S: \ 2010 \ NAHB \ C&D ELG \ C&D Final Rule Reconsideration \ Passive Treatment for C &D ELG final.doc  For the NCR.2 site McLaughlin paper (Exhibit 10) eliminated two of the nine rain events (22% of the original data) for which the Fiber Check Dam/PAM BMP was initially

evaluated.

As noted above, this is apparently a misinterpretation of the tables. No data ere s eliminated, but automatic sampler issues occasionally prevented samples from being collected. Anyone with experience with automatic samplers knows that they can be unreliable for a variety of reasons, but when they are working the y can provide excellent characterization of storm events.

 For the NC

- Road study, the PTS maintenance was supposed to be handled by site personnel, and not by McLaughlin or his associates. This involved polymer blocs upstream from a settling basin. The d ata was reported from 7 sites where the PTS was confirmed to be intact and functioning. However, the data from nine rain events, or 56% of the original data, was not reported. If the rain event or normal construction site activity (that did not directly co mpromise the PTS BMP integrity) was responsible for
the failures, then this data should be included.

The table (Table 3) refers to a single site with seven storm events, not seven sites. The primary treatment was with wattles with PAM applied to them. Installation and maintenance was handled by NCSU; site personnel were merely asked not to compromise the PTS or to notify us if they did, which they di d not. The data not reported were from rain events in which the PTS was compromised by the contractor, no t by runoff. Some examples include cutting a new diversion and inlet into the basin and installing a storm drain pipe that emptied into the basin, all without any soil stabilization or erosion protection. It does not make sense to include that data when evaluating PTS.

Also, from Exhibit 10, this site is described as being an LID site involving three buildings, and the paper suggests that the LID requirements came into conflict with the PTS. This is at odds

with EPA claims in the final TDD that this was another North Carolina Road project. It is very doubtful that Dr. McLaughlin originally wrote these papers with the intent of establishing a numeric compliance limit for an EPA rule. This means there may be reasons forrejecting certain data points whe n experimentally evaluating BMP effectiveness, but these reasons may no longer be appropriate for rejecting data that is being used to calculate a statistically supportable NEL. These PTS systems cannot usually be adjusted during actual rain
events, even i f operators are present to do so. Therefore, if these PTS “failures” occurred during the rain event and are caused by normal circumstances during that event, they should have been

included in the calculation of the NEL.

There also are a number of other inc onsistencies in data that was not collected at sites NCR.1 and NCR.2. For example, at site NCR.2 on 9/05/06, no measurement was taken (by the automated sampling device) due to “low flow” (in the table in the paper there was an entry of “LF” instead

of a value, which keys out to meaning “low flow”). However, this was on a day when there was a 58 mm (2.28 inch) rain event. It would seem impossible to have low flow for such a large rain event. Low Flow was again indicated for the 24 mm (0.94 inch) rain event on 7/21/06. In fact, there seems to have been a problem collecting data for all of the large rain events significantly above 1.5 inches. Most of the time, these are simply explained as “malfunction occurred”. What kind of malfunction? One would expect the se larger rain events to generate the highest turbidity, and these would also be the most likely events to overwhelm a PTS such as a fiber check dam. If that is what occurred, this is not a malfunction; it is merely representative as to how BMPs such

as Fi ber Check Dams/with PAM function in the face of large rain events.

The reviewers apparently did not read the footnotes in this paper. The Low Flow indications for NCR.2 (site 2 in the paper) cited above had a footnote that stated we were not certain that that was what occurred, but either way no samples we re obtained. Ag ain, no data were eliminated, but the automatic samplers did not collect samples. The three remaining LF events ranged from

7

- 17 mm (not “>1.5”, or 38 mm) and LF was highly likely because the wattle/PAM ditches had better vegetation and ground coverage. As indicated previously , a “ malfunction ” indication was for the sampler, not the PTS.

As can be seen, much data was already eliminated from consideration for these sites. However, EPA also intervened to limit the data still further, and in one egregious case completely alte red

the statistics for site NCR.2. NAHB recognizes that some of the EPA deletions were necessary, as in the following

circumstances:  For NCR.1 EPA deleted the 335 NTU result from 7/25/06 because some telephone crews had dislodged some of the fiber check dams (see page 6

- 8 of the TDD).


## SECTION 

# SEVEN

Page 43

S: \ 2010 \ NAHB \ C&D ELG \ C&D Final Rule Reconsideration \ Passive Treatment for C&D ELG final.doc  For both the NCR.1 and NCR.2 sites, there were rain events measured that took place after paving was finished and final vegetative stabilization of the site was underway. EPA deleted values measured after paving was finished. However, EPA had no technical basis for deleting the following points from NCR.2.  In the docket, EPA sent an email concerning two daily a verage turbidity data points from NCR.2, one was at 533 NTU and one was 261 NTU, stating that these were “higher than the rest of the data”. These were two of only seven daily average points for the site. EPA somehow felt that nearly 30% of all the data was somehow due to “outliers”. Dr. McLaughlin responded by email that (Docket ID: EPA

- HQ

- OW

- 2008

- 0465

- 2057) “thesespikes were likely due to site activities, but we don’t have anything more specific.” And “The sites were about three hours away so we couldn ’t keep track of all the activities.” However, these excursions are precisely the type one would expect if a rain event falls outside the narrow range where the PTS is most effective. Even the best PTS operators cannot always anticipate site conditions and rain events ahead of time, and unlike the ATS systems we have discussed, operators cannot intervene during the actual rain event. There are many appropriate site activities that are not a cause for eliminating these data points. EPA had no reason to delet e these points from the data, especially since there were so few points. As it turns out, the 261 NTU data point was measured well after paving was complete, which means that this turbidity was somehow present after the site was stabilized. This point woul d have been deleted anyway due to being collected after paving (see above bullet for explanation). However, EPA did delete the 533 NTU daily average data point. This rain event was an average of two samples, with the higher sample being 553 NTU.

This means the other sample was 513 NTU, so the turbidity was apparently constant over the rain event, and the measurement was no anomaly. The elimination of this data point is a major change, since the 533 NTU day was one of only four days

— 25% of the original data that was

left

— where measurements were taken prior to the road being paved at site NCR.2. The arithmetic average of the three other data points without this 533 NTU was 49.67 NTU. The average with this point included jumps to 170 NTU, along with a similar increase to standard deviation and variability. EPA had no sound technical justification for eliminating this point from the calculation, especially knowing that a similar high NTU happened again at this same site after paving had taken place.

Actually, the 553 in this table is Total Suspended Solids, not turbidity. In reviewing photos from dates near that storm event, it appears that paving activities were occurring. Part of the paving process is laying down a layer of “crush and run” stone, which is a mixture of stone and fines which compact into a stable support layer for the pavement. It is likely the turbidity spike was due to the fines washed from this layer prior to paving. These fines may not have been as responsive to the PAM we used as the local soil.Attac hment 1. Data From a 3 rd Site Near NCR.1 and NCR.2

The project which was the subject of one of the “true” PTS studies (McLaughlin et al., 2009; NCR.1 and NCR.2 in the URS document) had another road construction site which was monitored. This data was not included in the publication beca use there were relatively few storm events in which samples were obtained from all experimental sections of the road and because the PTS was destroyed during part of the monitoring period. However, the data is consistent with the two sites in the publicat ion, with turbidity reductions clearly evident when the PTS was intact (Table 1).

Table 1. Turbidity averages from a third road construction site not included in the cited article (Mclaughlin et al., 2009) because of relative lack of data for direct comparison by storm event. Empty cells in the table are the result of either sampler malfunction or low flow. All aspec ts of the monitoring were the same as described in the publication

.

Date Standard BMPs Wattles Alone Wattles + PAM

2007 Turbidity (NTU), number of samples in parentheses
Background Samples

(gravel road only)

1/4 1,015 (24)

1/5 1,679 (23

3/1 1,199 (24)

3/16 5,319 (24)

Road Construction

Starts

4/15 5,744 (24) 5,335 (24)

6/12 7,310 (2) 254 (24)

6/14 7,915 (5)

Wattles D islodged

6/29 4,771 (1) 10,308 (8)

7/17 3,470 (3)

7/25 3,951 (5)

7/27 5,302 (4) 7,157 (6)

8/26 3,840 (3)

Wattles Reinstalled

9/14 1,613 (15) 5,507 (24) 951 (24)

10/24 667 (8) 36 (9)

Road Paved

12/18 52 (2)

12/23 187 (6)

12/28 521 (11)
1/11 (2008) 171 (1)

1/17 23 (13)Attachment 2. Preliminary Data from a Current Project

We are currently conducting further studies on another NC DOT highway construction
project in ou r area. On two skimmer basins we have installed simple PTS and are

m onitoring at both the inlet and outlet. The site is in mass grading and highly disturbed

, but the BMPs are installed and maintained quite well

. The inlets are 12 ” corrugated
pipe with gravel/stone inlet protection , and each basin has a forebay with 12 ” corrugated
pipe overflow into the second chamber (Figure 1) . Coir netting was placed on the
gravel as a carrier for granular poly acrylamide (PAM) applied to the netting. We also
inserted jute netting into the upper end of each pipe, wetted the fabric, and applied PAM

to that. The storms we have monitored so far have produced flows in the 100

- 200
gallons per minute range, well b elow the design storm flows. However, as you can see

in Table 2, we have had very good results in reducing turbidity in these basins

.

Table 2. Average t urbidity in samples at the basin inlet an d outlet (skimmer) for two
basins on an active highway construction site in Wake County, NC

.

Date (2010) Basin 3 IN Basin 3 OUT Basin 4 IN Basin 4 OUT

Rain total in
parentheses. Average Turbidity (NTU) , number of samples in parentheses.

9/29 (2.1 ” ) 386 (24) 267 (24) 213 (24) 34 (5)

10/14 (0.54 ” ) 5

, 490 (3) 32 (8) 29,500 (6) 175 (24)

11/ 4

- 6 (0.70 ” ) 5,880 (5) 57 (11) 777 (7) Sampler

Malfunction

11/ 17 (0.33 ” ) 17,000 (1) 73 (4) 21,600 (16) 124 (18)Figure 1. Photos of the inlet (top ) and forbay (bottom ) of Basin 3. The rocks with coir
fabric on them are for inlet protection from heavy sediment, which is settling in the ditch. Pipe inlet