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New S r k State Department of ~nvironmyntal Conservation

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MEMORANDUM

TO: Bob Schick FROM: Gardiner Cross SUBJECT: Newburgh Ecological Risk Assessment DATE: August 15,2001

The purpose of this memo is to present and document my interpretation of the background sediment data recently presented to us for Central Hudson's Newburgh MGP site. The interpretation presented in the report submitted to us in July is, in my opinion, significantly flawed. Rather than trying to force Central Hudson to do the right thing with this data (and incurring another delay of several months) I have examined the data in detail and prepared this alternative interpretation.

As you know, Central Hudson submitted a revised Ecological Risk Assessment in July (several months late) for the Newburgh MGP site. The principal ecological issue at the site concerns the presence of contaminated sediments in the Hudson River offshore from the site. Even Central Hudson has acknowledged that some remediation of these sediments will be required. However, the geographic scope of the remedy is still open to question, due to the likely presence of other PAH sources in the area.

A primary goal of the additional field work in the river during the 2000 field season was to determine background levels of PAH compounds in sediments. To this end, CHGE collected 37 samples between the north end of the MGP site and the Beacon-Newburgh bridge, located north of the city. In addition, we requested that they collect a series of additional samples to the east of the known contaminated zone, in order to better define a "clean line" which could be agreed as the boundary of the contamination.

Statistical Approach

We agreed prior to the initiation of field work that we would use the EPA's "95 percent upper confidence limit (UCL)" approach to determine a background value from the data collected in this study. Stated briefly, this technique determines a conservative estimate of the mean concentration value for a population using a set of random samples collected from that population. It is NOT the same as the 95Ih percentile of the sample concentration data. Rather, it is an estimate of the mean-a value derived from a group of samples, which will be equal to or greater than the true population mean 95 percent of the time. Basically, we're saying "we're quite certain that the mean is at or below this level."

Central Hudson's Presentation

It is essential that the sample data be normally distributed (or that the data can be normalized by a log transformation) in order to apply this technique. It is also essential that any statistical outliers

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from the nominally "backg;und" data set be excluded prior to ~ t a r t ;~ the calculation. The simplest way to evaluate this is with a histogram. Two histograms are presented in this report: Figure 8 shows the relative distributions of "background data" and "site data" while Figure 3-1 shows only the distribution of the background data, but on an expanded scale. Both of these histograms are significantly distorted in the report. Rather than use an arithmetic scale or a logarithmic scale on the X-axis, as is standard procedure, the scales on both figures start out as arithmetic at the left end of the scale, and then change to nearly-logarithmic at the right end. The effect is to understate the extent to which the "background data" is skewed, and thus to understate the extent to which the "background" data set contains outliers.

In 13 years of environmental work, I have never seen a histogram distorted in this way before. Rather than argue with the utility on how to redraw it, I have taken their data and done it myself and attached it to this memo. Note that at one level, the distortion is unnecessary, in that the data appears to be roughly lognormally distributed anyway.

Outliers

I have attached histograms of the background data set, using both arithmetic and logarithmic scales. I have also attached two maps showing the spatial distribution of PAH values: one showing the background data, and the other an enlarged view of the most contaminated area near the MGP site and the sewage treatment plant.

The report concedes that the two highest PAH values in the background data set "could be considered potential outliers." These two concentrations (348 and 689 ppm) are more than twice as high as the next highest value, and clearly stand out on a box-and-whisker plot of the log- transformed data. Ln addition, one of them is from the only sample which contained visible asphalt debris. As you know, asphalt commonly contains very high levels of PAH compounds. These compounds are tightly held in a solid matrix-unlike the MGP derived contaminants, PAHs in asphalt chunks should not be bioavailable. The report fails to discuss the presence of asphalt in this sample, and presents UCL calculations both with and without these two samples included. I would argue that both of these samples should be considered to clearly be outliers, and accordingly removed from the dataset.

Two other samples should be removed from the "background" data set as well. The two southernmost samples in the background data set were collected in the area immediately north (nominally upstream) from the MGP site. Samples BS-1 and BS-2 were collected less than 100 feet from previous sample location RS-9. All three of these samples contain elevated levels of PAH (59, 159, and 123 ppm, respectively). Fairly extensive "upstream" redistribution of tar impacts by tidal currents has already been demonstrated at this site. Since these two samples are affected by site-related contamination, they cannot be considered as background.

Calculation of UCL

The report calculates two alternative values for the 95 percent upper confidence limit: 87.9 ppm including the two recognized outliers, and 45.6 ppm without. Due to the inclusion of site-related contamination in samples BS-1 and BS-2, both of these values are high. Removing these two values results in a far more defensible UCL value of 30.7 ppm.

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t,, Applicability of the UCL-

It could be argued that even this adjusted value is a spuriously high estimate of background. High PAH values are not randomly distributed throughout the background sampling area. Rather, they are clearly clustered in two easily identified areas which correspond spatially with likely sources of PAH contamination. The first, at the north end of the survey area, is shown on USGS maps as a former petroleum terminal. The second is located at the foot of the hill below downtown Newburgh, in an area where several storm sewer outfalls are know to exist. I have attached a map showing the locations of these areas.

Every background sample which exceeds 20 ppm is located in one of these two areas. It could easily be argued that what this survey has found is three distinct areas of PAH contamination (the MGP site, plus the other two identified above) and that the true "background" value for this area is found in the spaces in between.

Given the overall proportion of the Newburgh waterfront represented by these samples (roughly a third of the background dataset), I don't plan on arguing that they should be excluded from calculation of background. Like it or not, the City of Newburgh is there, and ordinary human activities in the city are likely to continue contributing relatively low levels of PAHs for the foreseeable future. Contaminant levels at the MGP are several orders of magnitude higher than the values under discussion here.

Additional Concerns

A secondary objective of this study was to "close off' the extent of sediment contamination along the eastern boundary. A series of five additional samples was collected in the hopes of defining a "clean line" beyond which there was little or no MGP impact.

The additional sampling failed to do this. Rather, if showed pretty clearly that site-related PAH contamination extends beyond the limits that Central Hudson has presented to us in the past. Combined with the two southernmost "background" samples discussed above, the areal extent of sediment contamination is nearly twice as large as originally defined in the RI, and is not yet fully defined. Note that this is true even if Central Hudson's (very unconservative) background value of 87.9 ppm is accepted. One of the new "clean line" samples contained 177 ppm PAH.

The logical response to this would be to require yet another round of sediment sampling farther out into the river. However, water depths will increase rapidly as we do this and we'll be in the main shipping channel in another few hundred feet.

How to Proceed

I think we have enough data now to proceed to a rational and defensible decision on a remedy for this site, albeit one that Central Hudson won't like much. Rather than going back in the field yet again, I would propose going into the FS with five sediment cleanup levels:

1) Removal of visible sheens and tar only 2) Restoration to Central Hudson's lower background estimate (45 ppm) 3) Restoration to a very generous interpretation of site background (30 ppm PAH)

0 4) Restoration to 2 G P m PAH, corresponding to a "natural b%ak" in the background data 5) Restoration to PAH screening levels (4 ppm PAH)

Combinations of dredging, dry excavation, and capping would be considered under all three cleanup levels. However, a capping-only remedy has already been rejected by DFWMR (and us) because of the change in river bottom elevations involved and also due to concerns that the NAPL might move to the edge of the cap and enter the river at a new location.

Prior to beginning the FS, we need to examine the question of altering river bottom elevations in greater detail. Clearly, their initial proposal (in which the cap would have raised part of the contaminated area above mean low tide) is unacceptable. This would have amounted to restoring bottom habitat by destroying it altogether. Is this still true farther out in the river? Would a two foot clean sediment cap be acceptable if it raised the bottom elevation from -20 feet to -1 8?

Sample Location

BS1 BS2 BS3 BS4 BS5 BS6 BS7 BS8 BS9 BSlO BSl I BS12 BS13 BS14 BS15 BS16 BS17 BS18 BS19 BS20 BS21 BS22 BS23 BS24 BS25 BS26 BS28 BS29 BS30 BS31 BS32 BS33

Total PAHs ( P P ~ ) 59.42 158.79 2.09 11.4 19.93 8.58 10.05 12.27 10.04 8.92 6.84 7.87 9.34

Table 3-2

Newburgh Project Ecological Assessment

95% Upper Confidence Limit for All Data

Natural Log 4 . 0 8 4 2 sjt 1( p~,d& 5.067 % a WCLL 0.7372 2.4336 2.9922 2.1494 2.3076 2.5072 2.3066 2.1883 1.9228 2.0631 2.2343

data with screamers removed

BS3 BS4 BS5 BS6 BS7 BS8 BS9 BSlO BSl I BS12 BS13 BS14 BS16 BS17 BS19 BS20 BS21 BS22 BS23 BS24 BS25 BS26 BS28 BS29 BS30 BS31 BS32 BS33 BS34 BS35

Page 1 of 1

Mean (Trans. Data) (x): 2.4760 Standard Deviation (Trans. Data) (s): 1.564725

Hatatistic (H) (from Gilbert, 1987): %79tget 3.101 from the table) Number of Samples (n): 37 2.979

95% UCL: 87.9 90 (vr ln5 = %lo$

Page 1 of I

mean 2.1234 std dev 1.21 0045 H stat 2.6719 N samples 33

95 UCL 30.77348

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ER-M = 35 to 44.8 ppm 1 95% UCL of Background I I (Without Potential Outliers) = 45.6 ppm

ER-L = 4 ppm I I I 95% UCL of Background

I (With Potential Outliers) = 87.9 ppm

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I I I I I I I I I I I I

0-2 2-4 4-10 10-20 20-40 40-80 80-160 160-250 250-500 500- >lo00 1000

Total PAHs Concentration (ppm)

04/01 SYR DS~-DJH, MRC 20528001120528g02 CDR

NEWBURGH PROJECT ECOLOGICAL ASSESSMENT

FREQUENCY DISTRIBUTION OF TOTAL PAHS IN

HUDSON RIVER SEDIMENT

BBL B@SyD, BOUCK & LEE, INC. e n g i n e e r s & s c ~ e n t ~ s t s 1

Newburgh Background PAH Distribution Entire Dataset 1

log (PAH)

Total PAH Distirbution in Background Sediment Samples

69-1 37 138-206 207-275 276-344 345-41 3 4 1 4-482 483-551 552-620 621 -690

Total PAH's

Ranges 0-68 69-1 37 138-206 207-275 276-344 345-41 3 41 4-482

log ranges

1-2

32 2 1 0 0 1 0

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natural log ranges - 1 0-1 1-2 2-3 3-4 4-5 5-6 6+

1 6 4

16 4 3 2 1

TREES & BRUSH

RS-07

SE-008 RS-05 SE-010

RS-10 L ~ E D 374 FEET NORM OF Rs-09 d l 4

RS-l2 LQC4rED 6% T E T NORTH OF RS-09 RS-1' t.CUT3 1%' Y E T NCRTH OF RS-09 : E m

SE-026

Rs-03 B SEDIMENT SAMPLE

APPROXIMATE SCALE

m?-040

HUDSON RIVER

7w I \ I V C I U ~ I G nuau

Riverdale, New Jersey 07457 (973) 6 16-9700 FAX (973) 6 16- 1930

'L---" LETTER OF TRANSMITTAL

To:New York State Department of Environmental Conservation Date:August 1,2001 Bureau of Western Remedial Action Project No.CINEW007 625 Broadway, 1 lth lo or Albany, New York 12233-7017

Attention: Mr. Gardiner Cross

Subject:Sewage Outfalls from the City of Newburgh

We are sending you ( I( Attached) or ( - Under Separate Cover) the following:

Drawing No.

1

2

Remarks:Attached are figures showing the approximate location of the NPDES outfalls for the City. These locations were established based on descriptions provided in their pennit. Also included are photocopies of part of the City sewer map from 1941. edited in the 1950's. Based on the older map nearly all streets terminating near the river had discharged to the river. Another notable feature on the 1941 map is the presence of two pipes discharging from the end of South William Street, both cast iron (C.I.), one 72-inch and one 24-inch diameter. These were observed during sampling, with the smaller pipe sitting on top of the larger pipe. The presence of the 72-inch pipe may be significant due to its age as its origins may be traced back to the construction of a brick sewer (56 X 60) shown on the plan continuing up South William Street.

Signed: -.s- Timothy B. Egan V Project Hydrogeologist

cc: Clifford Case Esq.

Report No. Spec. No. Description

Location of NPDES outfalls for City of Newburgh Historic locations of discharge locations from -1941 for the City of Newburgh

No. of Copies

Copyright (C) 1997. Maptech. Inc.

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Copyright (C ) 1997, Maptech, Inc.