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50 Fort Avenue SESD IRA Completion 7-1-20 RECEIVE® J U L 0 6 2020 ID Emir =UlServices,Im CITY OF SALEM SIMMONS ENVIRONIVIENTAI,SERVICIES, INC. BOARD OF HEALTH 213 EI,m STREET SALISBURY, MA 01952 July 1, 2020 David Greenbaum,Health Agent City of Salem Salem City Hall 93 Washington Street Salem, MA 01970 RE: Notice of Phase I Initial Site Investigation, Tier Classification, IRA Completion South Essex Sewerage District Sodium Hypochlorite Release Release Tracking Number(RTN)#3-35700 Dear Mr. Greenbaum; Please disregard our previous correspondence regarding this matter dated June 18, 2020 that contained grammatical and typographic errors. In its place, please accept the following. We are pleased to submit notice that an Immediate Response Action(IRA)Completion Statement, Phase I Initial Site Investigation, and Tier Classification have been filed concerning a release of sodium hypochlorite from a broken underground chemical distribution pipeline at the South Essex Sewerage District treatment plant property at 50 Fort Avenue in Salem, Massachusetts (the Site). A copy of these documents can be reviewed online at MassDEP's website http//public.dep.state.ma.us/Searchable Sites2/Search.aspx. Alternatively, these documents may be viewed and/or copied at MassDEP's Northeast Regional Office at 205B Lowell St., Wilmington, MA 01887 by appointment by calling 978-694-3200 IRA Activities The initial release discovery was in June 2019 with detection of"bleach odor"from seepage at the base of a headwall on the shore of Cat Cove during an outgoing tide. The Massachusetts Department of Environmental Protection (MassDEP) was informed of the release of a reportable quantity and the Condition of Substantial Release Migration into a surface water. The initial response actions identified the ruptured pipe as the source of the release and its proximity to the alignment of a deep force main sewer that crosses Cat Cove and enters the Site at the headwall location. The force main trench was serving as a preferential pathway for flow of the bleach and contaminant movement was influenced by daily tidal flushing of ground water. Sampling of Seep A at the base of the headwall was conducted daily for free chlorine residual and by the end of July 11Page 978-463-6669-Fax:978-463-6679 LSPES:_____.. .'ASIMMONSLAW.COM KRSIMMONS @SIMMONS21 E.COM SIMMONS EmimnMCrkW Saviors.Inc. SIMMONS IENVIRONIVIENTAL SERVICES, INC. Z13 ELA/i STREET ,SALISBURY, MA 01952 it was estimated that the majority of the contaminant mass had already escaped into surface water and dissipated with no evidence of Readily Apparent Harm to the environment. By the fall of 2019 we concluded that the residual sodium hypochlorite had reacted within soil and ground water and been transformed into degradation products consisting primarily of chlorate with some chloroform and lesser concentrations of other tri-halomethanes and bromate that were also appearing within the discharge to Cat Cove in Seep A even though there was no residual free chlorine. Assessment of extent was complicated by the congested network of electrical, sewer lines, chemical piping, and drainage utilities within the densely developed Site. Later in the fall, a number of wells were carefully installed with the finding that a remaining mass of chlorate appeared to be concentrated in an area near the Odor B Building, situated over 200 feet from the sea headwall. IRA Plan Implementation Beginning in January 2020 and continuing through March 2020 we implemented pumping of groundwater in the area near the Odor B Building from IEI-102 to remove residual chlorate and halomethane mass to the extent feasible. After three months of pumping chlorate and VOC concentrations in IEI-102 had decreased by a full order of magnitude and had approached an asymptotic decline. However,VOC concentrations at IEI-102 remain above the applicable GW-2 Standard which is protective for vapor intrusion. Odor B Building is an unoccupied structure where sodium hypochlorite is used in air scrubbers to control odors from the sewage treatment process. Sampling of sub-slab soil gas beneath the Odor B building detected concentrations of chloroform above MassDEP screening criteria. Sampling of indoor air at Odor B Building would be confounded by the presence of hypochlorite reaction byproducts from the process operations. Thus. an Imminent Hazard Evaluation was conducted using the MassDEP default vapor intrusion attenuation factor with the finding that there is no Imminent Hazard for current use of the building or to utility repair workers for active utilities in the vicinity. Ecological risk characterization was conducted to develop the No Significant Risk target concentration for chlorate in the Seep A as an average of 6 mg/L of chlorate. Since the ground water pumping,dry weather discharge concentrations are below that target and analytical detection limits. However,chlorate concentrations in Seep A after rain events are above that concentration; and the average concentration in the past months is about 10 mg/L of chlorate. These conditions do not pose a Substantial Hazard to the environment in Cat Cove. 2 1 P a g e 978-463-6669-Fax:978-463-6679 LSPES 1QWASIMMONSLAW.COM KRSIMMONS @SIMMONS21 E.COM Emironmrnul5crvices.mc. SIMMONS ENVIRONMENTAL SIERVIC0, INC. 213 EI,1vi STREET SA.I,ISBURY, 1ViA 01952 IRA Completion Summary Immediate Response Action(IRA) activities were initiated at the Site to assess and control the sodium hypochlorite release. At this point we conclude that there is no Imminent Hazard or Substantial Hazard posed to human health,public safety, or the environment, and IRA activities are complete. As Permanent Solution has not yet been achieved,the Site will enter Phase II Comprehensive Response Actions as a Tier II Disposal Site. Phase II Scope of Work The scope and schedule of proposed Phase II activities is described further within the report and will focus on characterization of post-storm event sampling of Seep A, characterization of the vapor intrusion pathway at the Odor B Building, and whether it may be feasible to address the chloroform vapors in the ground by removal through a soil vapor extraction pilot test. Please contact our office at the letterhead address or by email at lspesgl@wasimmonslaw.com should you have any question regarding the information presented in the IRA Completion Statement, Phase I Initial Site Investigation, or Tier Classification. Very truly yours, �'A?42Z'Ifl�� William A, Simmons, LSP CC: Mayor Kimberly Driscoll 3 1 P a g e 978-463-6669-Fax:978-463-6679 LSPESQ1 L&WA SIMMONSLA W.COM KRSIMMONS@SIMMONS21 E.COM