Saint-Gobain Stormwater Sample Data Submitted

Saint-Gobain recently submitted data for samples collected as part of the Stormwater and Surface Water Source Investigation. The submittal can be viewed here:

http://www4.des.state.nh.us/IISProxy/IISProxy.dll?ContentId=4744493.

[The blog post “Elevated Levels of PFAS in Stormwater at the Saint-Gobain Facility (Fourth Post in a Series)” posted on September 27, 2018, provides a general overview of the Stormwater Investigation and includes links to relevant documents, including earlier analytical results.]

The purpose of the sampling was to assess potential sources of the PFAS previously detected in the stormwater. To that end, samples were collected from the roof down spouts and catch basins / manholes close to the facility, as well as from the stormwater outfall and the Merrimack River.

Most of the samples were collected on September 10, 2018, during the “first-flush” portion of the storm when stormwater first started to flow early in the storm. “First-flush” stormwater often contains the highest concentration of contaminants.  Additional “late-storm” samples were collected from the two manholes and the stormwater outfall to evaluate how PFAS concentrations change over the duration of the storm.

Of note, HFPDOA (“Gen X”) was detected in the samples, although at concentrations significantly less than PFOA, PFOS, and other PFAS analytes. These detections represent the highest detections of GenX in samples of environmental media collected from around the SGPP facility.

Some highlights of the results include:

Stormwater from Roof Drains

PFOA and PFOS ranged from 1,400 to 52,000 nanograms per liter (ng/L), (equivalent to parts per trillion, ppt) and 320 to 6,300, respectively.  6:2 Fluorotelomersulfonic acid ranged from 490 – 89,000 ng/L.  HFPODA (GenX) ranged from 10 to 150 ng/L. 

Stormwater from Manholes

PFOA and PFOS ranged from 1,000 to 20,000 ng/L and 460 – 4,200 ng/L, respectively.   6:2 Fluorotelomersulfonic acid ranged from 97 – 14,000 ng/L.  HFPODA (GenX) ranged from 4.6(J) to 110 ng/L. 

Stormwater from the Outfall on the Merrimack River (SGPP-Outfall 001)

The first-flush sample from Outfall 001 contained PFOA and PFOS at 2,500 and 53 ng/L, respectively. PFOA and PFOS concentrations were greater in the late-storm samples at 7,900-9,400 and 1,600-1,800 ng/L, respectively.  HFPODA (GenX) ranged from 1.7 in the first sample to 57 ng/L in the second sample. 

Surface water from the Merrimack River

Total PFOA and PFOS ranged from 4.5 to 350 ng/L and 1.8 – 35 ng/L, respectively. HFPODA (GenX) was not detected in any of the river samples included in this data submittal. 

Looking Ahead:

Saint-Gobain completed repairs to the stormwater system this week and will be evaluating the effectiveness of these repairs. The purpose of these repairs was to address dry weather flow and compromised section of pipe where stormwater could potentially leak out of the stormwater system.  After the stormwater sampling program is complete and the laboratory data has been validated by an independent validation company, Saint-Gobain’s consultants will submit a report to NHDES with recommendations to address the PFAS present in the stormwater.

Tips for reviewing the report:

Results of the laboratory analyses are presented in Table 1 of the data submittal and sample locations are depicted on Figures 3 and Figure 4 (Attachment D).  The wet-weather and stormwater source samples were collected from five roof drains (RD-MB-NW, RD-MB-NE, RD-MB-SW, RD-MB-SE, and RD-NMB), two manholes (MH-5 and MH-23), one catch basin (DI-34), two surface drainages (Drainage-001 and Drainage-002), the stormwater outfall (SGPP-Outfall-001), and from five locations in the Merrimack River (SW-MERR-101W, etc).

Many of the laboratory results have qualifying notes (qualifiers) associated with them.  These qualifiers convey important information about the lab results.  For example, a “U” notation after a value in the Result column of a lab report indicates that the chemical compound was not detected above the sample method detection limit.  For example, consider a result reported by the lab of “0.86 U” for PFOA.  The value 0.86 is the method detection limit and the “U” indicates the results were below this value.  A complete list of the laboratory qualifiers used in this data submittal is presented at the bottom of Table 1.