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HomeMy WebLinkAboutPSD-052-15 (I ilaring ,ton Planning Services Report If this information is required in an alternate accessible format, please contact the Municipal Clerk at 905-623-3379 ext. 2102. Report To: General Purpose and Administration Committee P C> Date of Meeting: October 5, 2015 PD- 03G_�S Report Number: PSD-052-15 Resolution: PO - 03A`l,5 PO - O3S - 15 File Number: PLN 26.14.1 By-law Number: Report Subject: Clarington Transformer Station Peer Review, Annual Update Recommendations: 1. That Report PSD-052-15 be received; and 2. That all interested parties listed in Report PSD-052-15 and any delegations be advised of Council's decision. Municipality of Clarington Report PSD-052-15 Page 2 Report Overview Council accepted funding from Hydro One to retain a hydrogeologist to peer review the Surface and Groundwater monitoring program imposed as part of the approval of the Environmental Assessment by the Minister of Environment and Climate Change. The Municipality's hydrogeologist is providing his annual update on the peer review. 1 . Background 1.1 Clarington Council and staff have been very involved with the proposed Clarington Hydro Transformer since March of 2012 including public information meetings, the Environmental Study Report review, and numerous discussions. The Minister of Environment approved the project in January of 2014 after consideration of the objections/comments of various agencies, Clarington Council and residents. 1.2 To address ongoing concerns from community members and residents, Hydro One proposed to Clarington to fund a peer review of their Surface and Groundwater monitoring program. Council accepted this offer at their meeting of June 16, 2014 by Resolution C-267-14. The peer review consultant, Mr. Steven Usher of SLR Consulting (Canada) Ltd. was retained in accordance with the Purchasing By-law and has been working with the residents, staff and Hydro One consultants since late October, 2014. 1.3 Council also approved a road use agreement contingent on the drilling of a deep monitoring well. In November/December of 2014 the deep monitoring well was drilled to bedrock (beyond the Thorncliffe Aquifer). The hydrogeologists (CLOCA, G360 Group, Stantec, SLR)jointly agreed that the MW-15 site on Hydro One property was the most relevant location for this borehole and monitoring well. The MW5-14 site already has monitors at 4 metres, 7 metres and 40 metres; the deep borehole monitor at 112 metres and another monitor at 52 metres were a result of drilling the deep borehole. This provides multi-level monitoring (or a nested cluster of boreholes and monitors). 2. Summary of the Peer Review Findings 2.1 The SLR report reviews the present state of the existing information and purposely does not address the process by which it was achieved. Their review included information from all parties, including Hydro One, Stantec, G360 Group, Enniskillen Environmental Association, the Conservation Authority, Clarington, the Ministry of Environment and Climate Change and the Oak Ridges Moraine Coalition YPDT-CAMC. The results are outlined below, their more detailed report is Attachment 1. 2.2 Drilling of the deep borehole confirmed the absence of a shallow sand lens at location MW5-14 which to the east hosts local wells. It also showed that the dense aquitard soils extended down some 76 m to the Thorncliffe Aquifer where several local wells draw their water. An intermediate layer of sand was found in the aquitard at 52 m, and is consistent with the depths of a second grouping of local Municipality of Clarington Report PSD-052-15 Page 3 wells. A groundwater monitoring well was placed in this layer. The borehole was extended into bedrock, found (as predicted by CAMC-YPDT) at about 129.5 m depth. 2.3 The Site Conceptual Geologic Model was refined as further drilling information was obtained. Figure 1 in Attachment 1, page 4, shows the current understanding. Based on the deep borehole it is now clear that there is a thin secondary aquifer embedded in the Newmarket Till and tapped by several residential wells in the area. The difference between the SLR conceptual model and the one proposed by Stantec in their Addendum Report #2, is that the consistent layer of sand lenses is connected. The work by 360 Group on the assessment of formational boundaries would be a helpful input but it has not yet been received. 2.4 The deep Thorncliffe aquifer, and the thin embedded sand layer in the Newmarket Till host many local wells. These aquifers appear to get their water from a greater distance to the north, probably the Oak Ridges Moraine. These deep wells are protected by the thick low permeable Newmarket Till, as anticipated by Hydro One, and are not at risk from the Transformer Station. 2.5 The more shallow Mackinaw wells derive their water locally, and not from the moraine. This is based on their depth, and the now documented tritium levels in the two sampled wells from this layer. Based on the water well records, wells tapping this layer are present along Winchester Road, and along Langmaid Road, but none exist south of the TS site. Further to this, cored boreholes drilled by Stantec show this layer is not present west and south of the site. The presence of a strong groundwater divide exists between the site and the closest Mackinaw wells in the Farewell Creek tributary near Langmaid Road. SLR concludes those wells are not at risk, and has suggested further monitoring will confirm this. 2.6 The ground and surface water monitoring program is comprehensive and typical of other programs in similar settings. 2.7 The water balance presented in the Addendum 2 to the Baseline Report by Stantec has been derived by acceptable methods. It has determined that the bulk of recharge water moves laterally through a surficial sand and the weathered till soils at surface. Thus discharge to surface water in low lying areas is important to continue to monitor. 2.8 The Permit to Take Water process put in place a rigorous daily water monitoring program for water handling procedures, with weekly reporting mechanisms. SLR has reviewed these results as they became available. Water quantities have been much lower than anticipated, and very little ground water contribution has been seen. SLR also conducted a site visit on September 11, and reports that water handling procedures are operating as anticipated with no obvious signs of vegetative distress or uncontrolled discharge. 3. Concurrence Not applicable. Municipality of Clarington Report PSD-052-15 Page 4 4. Conclusion 4.1 The purpose of retaining a peer review consultant was to assist with understanding the technical information and to have an independent advisor monitor the practices and methodologies being employed during the construction of the Clarington Transformer Station. To date, the observations, recommendations and conclusions by Mr. Usher of SLR Consulting (Canada) Ltd. have required additional work by Hydro One and their consultants to demonstrate that the conclusions of the Environmental Assessment and Permit to Take Water are reasonable and conservative. 4.2 Council and residents were concerned for the safety of private residential wells in the vicinity of the transformer construction and Farewell Creek. To date the transformer construction has had no adverse impact on residential wells and discharge to the creek as demonstrated by the recent monitoring report. 4.3 Much has been learned about the hydrogeology of the site over the past year, providing additional scientific knowledge for the G360 Group researchers, and the Oak Ridges Moraine Coalition, YPDT-CAMC. 5. Strategic Plan Application Not applicable. Submitted b y: Reviewed by: Da6id trome, MCIP, RPP FrEinklin Wu, Director/of Planning Services `/ Chief Administrative Officer Staff Contact: Faye Langmaid, Manager of Special Projects, 905-623-3379 ext. 2407 or flangmaid(@clarin_ toq n net Attachments: Attachment 1 — Clarington Transformer Station Peer Review The following is a list of the interested parties to be notified of Council's decision: Brad Bowness, Hydro One Clint Cole, Enniskillen Environmental Association Drs. John Cherry and Beth Parker, Group 360, University of Guelph Dr. Rick Gerber, YPDT-CAMC Chris Darling, CLOCA Steven Usher, SLR Consulting (Canada) Ltd DJC/FL/sn/df Municipality of Clarington Attachment 1 to Report PSD-052-15 SLR September 28, 2015 Municipality of Clarington 40 Temperance Street Bowmanville, ON L1 C 3A6 Attn: Faye Langmaid RE:SLR PROJECT NO: 209.40261.00000 CLARINGTON TRANSFORMER STATION PEER REVIEW 1.0 INTRODUCTION SLR Consulting (Canada) Ltd. (SLR) has been retained (November 2014) by the Municipality of Clarington (Clarington) to provide peer review services of the Hydro One Clarington Transformer Station (TS) ground and surface water monitoring programs. SLR also provides technical advisory services to Clarington staff and Council, and for the local residents as well. The TS was approved by the Ministry of Environment and Climate Change (MOECC) in January 2014 and pre-construction of roads and tower relocations began in the autumn of 2014. As part of the background information, Hydro One provided both the Enfield TS and Clarington TS EA documentation, however a peer review of that information is beyond the scope of SLR's contract. There are several groups of stakeholders, with which SLR has had close contact as part of reviewing the monitoring program. Hydro One retains Stantec to provide technical expertise. The Municipality of Clarington has jurisdiction over the road allowances, but does not have approval authority over proposed site activities. The Central Lake Ontario Conservation Authority (CLOCA) has provided technical review as the site falls within their jurisdiction. Local residents fall into two groups, neighbours who are part of the well monitoring programs, plus those affiliated with the Eniskillen Environmental Association (EEA), a group of concerned citizens including both neighbours and local people concerned with the potential effects of the facility. The EEA retained Group360 of the University of Guelph (Dr. John Cherry) as a hydrogeological peer reviewer. CLOCA has also relied on Dr. Rick Gerber of the Oak Ridges Moraine Hydrogeology Program (YPDT-CAMC) to provide regional hydroge000gic information. The MOECC is the approving authority of the environmental assessment (EA) and other approval instruments, such as the Permit to Take Water (PTTW). Mr. Steven Usher, P.Geo., P.Eng, a senior hydrogeologist with over 35 years experience in Ontario and specifically this terrain, has been the primary reviewer for SLR on behalf of Clarington. Ms. Dale Leadbeater, B.Sc.,R.P.Bio, a senior ecologist, has provided support on ecological issues. Mr. Usher has been the primary contact with the stakeholders. SLR Consulting(Canada)Ltd. 200-300 Town Centre Boulevard,Markham,ON L3R 5Z6 T:905.415.7248 F:905.415.1019 www.slrconsulting.com Municipality of Clarington Project No.: 209.40261.00000 Clarington Transformer Station Peer Review September, 2015 2.0 METHODOLOGY SLR was retained on October 30, 2014. As a preliminary step, the existing technical documentation was reviewed to become familiar with the site specific information and that in the immediate vicinity. This included the following documents: 2013 EA Application documents by Stantec • 2013,2014 correspondence between MOE (now MOECC) and the proponent • 2014 EA approval, dated January 2014. • November 2015 Updated hydrogeological technical appendix • EEA submissions • Group 360 technical review by John Cherry • 2012 CLOCA review • 2014 Addendum 1 to Baseline Conditions (Stantec) • 2015 Addendum 2 to Baseline Conditions (Stantec) • 2014 PTTW Application (Stantec) This information was reviewed on an ongoing and as-received basis from November 2014 to date. Five formal meetings were held with the public stakeholder group, and at least six visits to people's homes were conducted, two of which included well or plumbing inspections. A total of nine site visits were undertaken with Hydro One, plus one "windshield survey" with local residents to identify pertinent features. SLR has made two appearances in front of Council, and one in front of the Durham Joint Committee. SLR also participated in three meetings with the MOECC, representing Clarington technically on the review of the PTTW application. Finally, we have participated in several technical meetings by teleconference as the different field programs were conducted by Stantec and Group360. 3.0 SCOPE This review is focused on the Clarington Transformer Station. It is intended to deal with the information as it stands to date. Early in the process there were many questions raised, and many of these were addressed with further works. It is beyond the scope of this review to comment on process, or the regulatory approvals given. The focus has been on understanding the hydrogeologic setting and understanding the implications of this facility on this setting, the natural environment, and the local groundwater uses such as private wells and watercourses. 4.0 EA REVIEW The 2007 and 2013 EA submissions were reviewed to gain historical context and to understand the level of hydrogeological and ecological technical detail. This was not a formal peer review. The hydrogeologic submissions were based on a review of regional information such as geology maps and local water well records, coupled with on-site geotechnical drilling results. No hydrogeological drilling or groundwater testing was initially completed. As the approval process proceeded, onsite hydrogeological work SLR 2 Municipality of Clarington Project No.: 209.40261.00000 Clarington Transformer Station Peer Review September, 2015 was carried out with the installation of groundwater monitoring wells in late 2013. Further drilling and testing in response to Clarington and MOECC enquiries has been carried out in 2014 and 2015 subsequent to MOECC approval of the EA in January 2014. The EA submission concluded that the site was characterized by a very thick layer of dense sandy silt till with unconnected sand lenses. The site design went forward on this basis and includes a level transformer station created from cutting the east side of the site down and using that soil material to backfill the west side. An underdrain system is planned that will collect all surface water and any groundwater and convey it to the existing watercourses. Monitoring of water quality is part of the plan. Spill controls are planned to contain any should transformer leaks with time or accidental breaches. The EA submissions did not present any form of conceptual hydrogeologic model, which is typically used to direct site investigations. Through the review process many questions have been asked and Hydro One has responded by drilling on an as-needed basis. Upon retainer by Clarington, SLR presented a conceptual model based on the information collected to date in November 2014 to staff, Council and the public. As the various drilling programs added information, particularly a 129.5 m deep corehole to bedrock at MW5-14, the conceptual model has been updated and is presented in the following section.' It should be noted that the November 2014 Baseline report by Stantec provided a conceptual hydrogeologic framework utilizing the recent drilling results to date at that time. This was updated in Addenda 1 and 2, as further drilling results became available and in response to questions on the water balance for the site. 5.0 CONCEPTUAL SITE MODEL To help put the site in context the following conceptual site model has been prepared based on the on-site data, local water well records and our knowledge of the regional geology. This is presented to provide a framework and terminology within which to understand the site. The conceptual model most recently presented by Stantec is subtly different and will be discussed in the context of the following framework. Regionally, the geology of the south slope of the Oak Ridges Moraine is quite consistent over the almost 200 km of its length. The underlying shale and limestone bedrock is covered by a series of layers that are as identifiable here as they are in Pickering or Brampton or Northumberland. Indeed the deep corehole drilled at this site to the bedrock at MW5-14 identifies these layers consistently in comparison to others in the region. Figure 1 on the following page shows the conceptual geologic model for the site. 1 All well locations are shown on Figure 2 on page 13 of this letter report. SLR 3 Municipality of Clarington Project No.:209.40261.00000 Clarington Transformer Station Peer Review September, 2015 �� NLINE sS' F i TRANSFORMER ,TOtK �\ SITE _ �p0 �N i0� m P�� NFST�R ROAu a � ALTON TILL H ----- � F , Eg MACKINAW(7) L m �j DEEP �- m HOLE NEWMARKET 10��61NE _ TILL = o, NEWMARKET TILL / 1pdm ii// THORNCLIFFE AQUIFER \ BLUE SCARBOROUGH AQUIFER \� � h MOUNTAIN SHALE,LIMESTONE i / Figure 1. Conceptual Geologic Model SLR 4 Municipality of Clarington Project No.: 209.40261.00000 Clarington Transformer Station Peer Review September, 2015 The stratigraphy is described from the bottom up. A silty sand aquifer called the Scarborough aquifer (orange layer on Figure 1) lies directly on the bedrock (found at a depth of 127.8 m and shown in blue at the base of the conceptual model in Figure 1). The Scarborough aquifer is protected by the Sunnybrook drift (red layer on Figure 1). The deep corehole at MW5-14 found the Scarborough was about 16 m thick at the site. The Sunnybrook drift is a 7 m thick interebedded clay and silt. These deep deposits are older than, and underlie the Thorncliffe Aquifer (yellow layer on Figure 1), a sand aquifer of substantial thickness which grades finer with depth to silt. The upper part of the Thorncliffe is a regional aquifer covering many 100's of square kilometers in southern Ontario. Many of the private wells in the study area tap the top of the Thorncliffe Aquifer. At MW5-14 it is 29 m thick, and the upper less silty portion is about 17 m thick. The confining layer to the Thorncliffe is a diamict called the Newmarket till shown in light green on Figure 1. This very dense and low permeability material is a sandy silt till, and is regionally extensive. It in fact underlies the Oak Ridges Moraine to the north of the site. In the conceptual model shown on Figure 1 it is sometimes at surface, and sometimes overlain by the Halton Till (dark green layer on Figure 1) where present. Drilling at MW5-14 shows t that the Newmarket has three distinct components. The lower till is a mixture of dense diamict with silty and sandy lenses. There is a 3 m thick layer of sand and silty sand at a depth of 52 m (shown as the thin yellow layer in the light green Newmarket Till on Figure 1). This unit is seen in several local wells and has been known to exist 10 km or more from the site. The upper 48 m is a very dense and uniform sandy silt till of very low permeability, and represents a very competent and thick protective layer for the deeper aquifers. It is pictured at left on this 50 mm sample. At the ground surface, there is a discontinuous skiff of sand shown in a photograph of the excavation at left. In addition, the glacial till ` (where exposed at surface), exhibits a shallow weathered horizon where freeze-thaw cycles, reduction and oxidation, root penetration � x and a lack of overburden weight have enhanced the permeability. This is conventionally taken to be 3 to 5 metres in depth, however 1 ~- physical observations in recent excavations suggests this is less ` than 3 m at this site. SLR 5 Municipality of Clarington Project No.: 209.40261.00000 Clarington Transformer Station Peer Review September, 2015 The weathered zone coupled with the surficial sand is a significant shallow pathway for lateral groundwater movement. + ► The photograph at leftt shows the surfaces of the fractures in ,-� - the weathered zone that are highlighted by iron oxides where 4L = the water table fluctuates seasonally. To the north of the site, the Newmarket till is blanketed by the Halton Till. At the Oak Ridges Moraine (ORM) the Halton Till overlies the moraine directly, but the ORM deposits pinch out to the south towards the site. The contact between the two tills is often occupied by thin layers of sand and gravel or sand, called the Mackinaw deposit (shown in bright yellow on Figure 1). At this site, the Mackinaw was not observed in the deep corehole, nor in the boreholes at the western portion of the site. A deposit like the Mackinaw is seen in several boreholes on site, particularly to the east, but is not differentiated in the Stantec borehole logs as such. They do lie at similar depths. To the east of the site, towards Langmaid Road, there is strong evidence of the Mackinaw in that Farewell Creek is groundwater fed where its channel incises the till, and there are many wells that draw water from about 10 to 15 m depth. The most recent conceptual model presented by Stantec in their 2nd Addendum to the baseline report, does not acknowledge the Mackinaw, and is explicit in refuting the presence of the Halton Till. The sand deposits are all stated to be discontinuous and local and embedded in the Newmarket Till. Regardless of the naming convention of the tills, there is a consistent horizon of these sand lenses, and without proof that they are not connected, it would be wise to examine this possibility. SLR proposed the use of a pumping test during the review of the PTTW application but both the MOECC and Stantec did not believe it was necessary. The EEA had suggested, through Dr. Cherry of Group360 that tritium be used to help date the groundwater to examine this possibility. Hydro One has elected not to do this. (The EEA did this on selected private wells in the summer of 2015, which will be discussed below.) To be prudent, this report adopts the conceptual model presented above and shown on Figure 1. 6.0 PTTW REVIEW In order to excavate the site and fill it to make a level site area for the transformer station, Stantec conservatively estimated that the construction would generate more than 50,000 L/day during the first months of construction. This amount triggers the need to have a Permit To Take Water (PTTW) Clarington was given the opportunity to review this application, which SLR did on their behalf. Seven issues were raised with the application and Hydro One had Stantec drill additional boreholes as well as modify the design in places for water control. (Specifically, a lined ditch was added along the top of the excavation to capture surface water from entering the excavation.) During the review SLR asked what the implication of the Mackinaw would be on ground water control at the site. We identified that BH7A-D, drilled for geotechnical reasons SLR 6 Municipality of Clarington Project No.: 209.40261.00000 Clarington Transformer Station Peer Review September, 2015 where the transformer foundations were planned, showed significant sand at 7 to 13 m depth (BH7B, BH7D). Stantec drilled Borehole MW8-15 in January of 2015 and encountered a sand and gravel unit at 13.3 to 14.2 m. This is listed on their borehole log but not identified as a separate unit. The groundwater monitor constructed in this borehole exhibited a hydraulic conductivity of 7 x 10-6 m/s, which indicates a sand. If the sand is unconnected this is not an issue for the site, however if it were close to surface where the deep oil/water separator tank is to go, then a connection to depth could inadvertently be created. The MOECC agreed that there was potential and requested a borehole directly at the tank location. Stantec drilled 131-19-15 in late March to a depth of 10.1 m, well below the tank bottom. No sand was found. During the PTTW review process, SLR and Clarington met with the MOECC on three occasions to review the issues and proposed resolution. The concern for a connected presence of the Mackinaw from the east side of the site towards wells along Langmaid Road was raised. SLR recommended an additional monitoring well between the residents and the site, however the MOECC felt the present monitoring program at MW1 would suffice as an early warning location. In addition, the MOECC did not agree with the recommended pumping test in the Mackinaw sand, reasoning that the wells were too remote, and if a problem did occur the shallow well (PW16) in question could be deepened. The PTTW was approved in late May. As of this writing the excavation is almost complete. Hydro One has been issuing weekly summaries of their pumping and discharge monitoring, and Stantec has provided monthly summaries of the groundwater monitoring. SLR reviews these summaries each week and was invited to inspect the site and just recently completed this site visit. The water is collected at the north and south ends of the excavation by gravity sumps, and pumped into decant tanks. As the tanks near capacity, the clear decant water is pumped to a shallow engineered pond with filters. As of this writing, 144,000 L has been collected on the north side, and 13,000 on the south side. No discharge has been needed on the south side, and about 100,000 L has been released on the north side. The turbidity of the discharge is measured by automated meter, and has generally been less than 1 NTU, well within the required criteria. No significant groundwater inflows have been identified and most of this water is surface water generated by precipitation. 7.0 GROUNDWATER BALANCE The EA documentation did not present a water balance. The baseline report did, however the mixture of units (mm/yr, L/s and m3/yr) made it difficult to interpret and when tallied it did not add up. In particular, more than half of the recharge water was unaccounted for, and indeed this initial attempt did not include either the Mackinaw or surficial weathered till or sand pathways. This was discussed in meetings with Stantec, and in Addendum 2, an integrated water budget was presented. We have reviewed the formulation and mathematics and find the methodology acceptable. The following table summarizes the water balance prepared by Stantec. SLR 7 Municipality of Clarington Project No.: 209.40261.00000 Clarington Transformer Station Peer Review September, 2015 Component Annual Water Movement (m3/r) Recharge 12,504 Lateral movement in surficial sand -9,548 Lateral movement in the weathered glacial till -1,535 Downward leakage to deeper aquifers through glacial till -1,958 Difference -537 This is a reasonable result if one assumes that the surficial sand is connected at surface, and where it is not, the weathered till can convey water from the surficial sand. Since Stantec has assumed that all deeper sand lenses are unconnected, there is no pathway considered in the Mackinaw if it were present. The implication of a connected Mackinaw, is that it may provide an additional lateral pathway that could also balance the "water in —water out", should there not be enough connectivity in the surficial sand. Since it is unaddressed in any of the documentation, it is prudent to examine this possibility and significance. Evidence of a Mackinaw layer is seen in the following boreholes: Location Thickness Depth Elevatio Rationale (m) (m) n (masl) MW1- 0.9 9.5 253.1 Hydraulic Conductivity = 9x10 m/s, typical 13D of sand, reported as distinct layer. MW8-15 0.9 13.3 241.1 Same general location as BH7A-D Hydraulic Conductivity = 7x10-6 m/s, typical of sand Washed out core, not reported as distinct layer BH6 2.1 11.7 244.0 Geotechnical hole, reported as distinct layer, no groundwater monitor BH2 1.6 5.7 247.3 Geotechnical hole, reported as distinct layer, no groundwater monitor BH11-12 1.8 13.7 238.6 Geotechnical hole, reported as distinct layer, sli ht artesian condition BH12-B 1.5 8.7 230.8 Near Langmaid road. Farewell Creek gains groundwater in this area, and other private wells (e.g.PW1) tap this same layer around 230 masl. 2 Hydraulic conductivity is a term used to describe the ability of the soil to conduct water. Aquifers generally have a hydraulic conductivity of greater than 10-6 m/s, and aquitards are less than 10-6 m/s. SLR 8 Municipality of Clarington Project No.: 209.40261.00000 Clarington Transformer Station Peer Review September, 2015 Location Thickness Depth Elevatio Rationale (m) (m) n (masl) BH4 Not >10 m <242 Geotechnical hole, reported wet sand Determined seams, no groundwater monitor It is also important to understand where there is no evidence of Mackinaw sand. Location MW5-14 was fully cored borehole with no presence of sand. MW3 and MW4 were also core holes with no presence of sand. These three wells are west and south of the transformer station. MW6, MW7 and BH9-15 were too shallow to encounter sand if it were at the Mackinaw horizon. Several geotechnical holes did extend far enough down, BH3, BH5, BH12-12, in this vicinity, but were only split spooned sampled so any layer less than 1.2 m thick between samples could have been missed. Of some interest, all the wells that exhibited sand (or are inferred here to possibly have sand) have a head that is near ground surface, similar to the shallow monitor at each location. All the wells that did not see sand, where there was a groundwater monitor, had a head at depth indicating a very strong downward gradient and quite typical of glacial till in our experience. This implies that recharge for a sand layer comes from the ground surface, likely laterally from nearby hills. BH11-12 was decommissioned to permit tower foundation construction. Based on the earlier reports, and anecdotal evidence from the public, Hydro One and Stantec, this groundwater monitor was artesian with a head a few centimeters above the top of pipe. Estimates of flow were in the order of 0.1 to 0.5 L/min. For this well (which was down by the wetland north of the site) to be artesian, the water would not be able to drain laterally away. This is consistent with the absence of sand to the north (BH12-12) and west (MW3-13, MW5-14), and ultimately to the south (MW4-15D). However to have a head above ground also means that it is connected to something with a higher head, likely to the east (MW1-13) and immediately to the south (131-12, BH6, MW8-15). To examine if this is reasonable, one may calculate what area of a connected Mackinaw sand lense would be needed to generate up to 0.5 L/min. To calculate the rate of recharge, the vertical downward gradient at MW1 of dh/dL = 0.4/5.3 = 0.075 m/m is used, along with the unweathered till hydraulic conductivity of K = 7x10-9 m/s. By Darcy's principle the flow per unit area is: Q/A = K x dh/dL = 7x10-9 m/s x 0.075 m/m = 5.25x10-10 m/s, or 3.15x10-8 m/min SLR 9 Municipality of Clarington Project No.: 209.40261.00000 Clarington Transformer Station Peer Review September, 2015 Rearranging this equation to determine A, and knowing the flow of 0.5 L/min = 0.0005 m3/min: A = Q / 3.15x10-8 m/min = 0.0005 m3/min / 3.15x10-8 m/min = 15,875 m2, or just under 1.6 ha To get an idea of the sensitivity of this calculation, a stronger downward gradient would reduce the calculated area. Similarly a higher hydraulic conductivity would also reduce the calculated area. The area encompassed by the boreholes showing evidence of Mackinaw sand is about 6 ha. One would therefore expect much more water than was observed. Based on this analysis, it does not appear that the connected part of the Mackinaw sand is laterally extensive. This is consistent with the observations around the site periphery to the west and south. The presence of groundwater contributions to Farewell Creek just west of Langmaid Road, is consistent with the elevation of the Mackinaw seen in some of the local wells, and implies connectivity in that area, east of the site. 8.0 CONTAMINANTS OF CONCERN The Environmental Assessment identified the nature of the materials on the site once it is up and running. The insulating oil for these transformers is planned to be mineral oil, which has become the industry standard as an inert compound for this purpose. Through the Group360 review, residents raised the concern of what this oil might impact if released to the environment, the EA did not explore that in any detail, but rather relied on several levels of contingency. The transformer station is designed with spill containment of which the containment volume exceeds the volume of oil on site. Slow, progressive or catastrophic leaks will typically be captured. If this system fails, it is most likely by slow leaks, and the material would enter the underdrain system. Fluid follows the path of least resistance and much of the oils would be captured by the underdrain, however they would come into contact with the glacial till soils below. Since excavation of the underdrain beneath the transformer is impractical, the assessment should focus on the ground and surface water pathways in the till, and the effects of the contaminants there. Where unweathered soils are of very low permeability, and as long as they are not connected to any of the deeper Mackinaw sand, where present, the travel times are low and there is sufficient time to detect and remediate any groundwater threats. For example, the average linear ground water velocity in the glacial till soils is a function of the hydraulic conductivity (K) of the soil and lateral hydraulic gradient (dh/d L), and may be calculated from the simple relationship: V = (K x dh/dL ) / n, where n is the soil porosity. SLR 10 Municipality of Clarington Project No.: 209.40261.00000 Clarington Transformer Station Peer Review September, 2015 These parameters have all now been measured at the site, and assuming the highest measured K for the unweathered till soils of 7x10-9 m/s, the maximum measured horizontal gradient of 0.45, and the measured porosity of 16% (n=0.16) for the unweathered till, the average linear groundwater velocity is about 0.6 m per year. Most of the underdrain lies on the unweathered till, or compacted till soils. Should contaminated water reach the unweathered till at the perimeter of the facility, the same calculation can be made. Here, the hydraulic conductivity is 1x10-6 m/s, the maximum measured gradient is still 0.45, and the measured porosity is higher at 21% (n=0.21). The ensuing average linear groundwater velocity is just under 70 m/yr. In both cases there is sufficient time to remediate. This point has been made in the Hydro One documentation and is an acceptable approach in many applications in industry today, provided sufficient operational monitoring and perimeter groundwater monitoring is undertaken. The residents have also raised the possibility of catastrophic explosive failure, spreading contaminants through complete meltdown of the facility. This is beyond the scope of our retainer to assess, but we do note it is not covered in the existing documentation. Typically such things are addressed through risk assessment based on the performance of other similar facilities, and the design of the current facility. 9.0 PRIVATE WELL SAFETY The Hydro One documentation concludes that private wells are not at risk from the construction or operation of this facility. Members of the Enniskillen Environmental Association continue to express concern about the safety of their wells. For the past year they and other members of the public have been participating in a well monitoring program. SLR has met privately with six local residents to review the monitoring results for their wells. There have been issues with bacteria in several wells, and one home had low but measureable benzo(a)pyrene in the well on one occasion. The meetings were confidential and the specific details will not be discussed here. In many cases, the documentation provided by Stantec to the homeowners concluded that localized issues with the wells (e.g. well construction, land use and well operation) were not caused by the TS site. SLR did not conduct well inspections, but was able to put the individual issues into the context of our experience with local wells. What was not well expressed in the well reports were the reasons why Stantec did not believe the site was at fault. To aid in future assessment, we take this opportunity to apply the conceptual model presented above (Figure 1) to put each aquifer into context with respect to groundwater flow to or from the site. This is done from the lowest aquifer, progressively up to the aquifers closest to the surface. The Thorncliffe aquifer, shown as a wide band (coloured yellow) on Figure 1, is utilized by almost half the local wells in the area. It is typically 70 to 90 m below ground surface. Regional modelling of this aquifer (CLOCA, 2012) shows that it has a groundwater flow direction that is southerly in direction, and it is commonly held that its water originates at the Oak Ridges Moraine (6 km north of the site). In the SLR presentation to Council in December 2014, it was stated that our own assessment of SLR 11 Municipality of Clarington Project No.: 209.40261.00000 Clarington Transformer Station Peer Review September, 2015 water levels in the private wells in this aquifer confirmed CLOCA's inferred direction of groundwater flow. We used specific capacities determined from the well records to estimate aquifer hydraulic conductivity, and then applied that and the measured gradient to determine that the rate of groundwater flow was about 100 m per year. We also showed that only about 20 mm/yr of leakage per square metre moves downward through the overlying Newmarket Till aquitard. On this basis we conclude that those wells that derive their water from the Thorncliffe Aquifer, are using water that has originated from the ORM to the north and not from under the site. Assuming the wells are secure (that is, no leaking casing), there is very little risk of being affected by the operation of the Transformer Station. The Conceptual model also identifies a 3 m layer of sand within the Newmarket Till, but at a depth of 50 to 60 m. It is inferred that this layer too extends locally (within 10 km) and will also be deriving its water from the ORM. For the same reasons as above, there is very little risk of wells in this unit being affected by the operation of the Transformer Station. Recently, the results of Tritium testing conducted by members of the EEA were made available. These results are discussed briefly below, and it is shown that they reinforce the interpretation that the deep aquifers are not threatened by the facility, as the water appears to be many decades old. There are several wells which derive their water from the Mackinaw layer, particularly near and along Langmaid Road (MOE Well numbers 7157947, 1903520, 1903352). The layer seems to be absent south of the site (MOE Well numbers 1912622, 1918378, 7208110), but can be seen again in wells along Winchester Road in Oshawa (just west of Townline, MOE Well numbers 4600450, 4600451, 1905326). Given the discontinuity of this layer (as demonstrated at the site and in the local well records) it is unlikely to be recharged by the ORM to the north. Certainly the theoretical analysis presented above on this layer showed it would not take much extent (1.6 ha) to derive it's water locally there. The tritium results discussed below reinforce that. The Mackinaw would have to be near surface and close to the weathered till and surficial sand to receive sufficient recharge. Given that the Mackinaw (where present) may derive its recharge from surface, then the direction of groundwater flow in the unit is important, to understand which wells may be downgradient from the site. In the PTTW application, Stantec presents a map (Figure 7) of the measured water levels in wells screened down to 16 m below ground surface, reproduced below as Figure 2. The yellow shaded area has been added by this author and represents the downgradient area from the site. Only well PW22 (MOE No. 1918378) is directly downgradient, but is screened in the deep sand layer embedded in the Newmarket till at the 48 m depth, and not in the Mackinaw, which was not present in the driller's log for the well. The Mackinaw wells to the east are protected by a groundwater divide under the hill running north-south, east of the site (shown as a dashed yellow line, added by this author to Figure 2). Groundwater does not flow SLR 12 Municipality of Clarington Project No.: 209.40261.00000 Clarington Transformer Station Peer Review September, 2015 across a groundwater divide. The Mackinaw wells along Winchester Road are potentially downgradient, and we understand that PW13 (MO no. 4600451) is part of the monitoring program3. It is important to note that MW3-13, MW4-15, and MW5-14 are intermediate between the site and PW13, and do not have any Mackinaw present. t- PW-16 250.2 �;•� _ �r•� MW6-14 N N i,��•' O"!!, 260-4 h �,,�•'� • DP2-13;DP2-14 ' T P 3-15,A N PW,10 ' 1 . 249.9x' S 13 H11-12%" MW1 3 ..r•'�•r tt TP2-14 ` 261.8 ,mry MW2-13 ♦ ♦ • a• �tC i ' TP1-14" MW7�13 SW3 kb BH7A ' i' 262:0 I o DP3 1'4 MW3113 MW5.14 240 239.9 2. .? ; p. „♦ c ` 9 BH2.12 BH4-12 J i SW4 • /// PW-01 230 Ir1 �,.i• 0 P4-13*MW4-13 •r�''i • �J 237.2 PW03 2336 •� ,�•' 238:Li A PW-04 PW-20 —PW-1.2 24,1'9 235.1 PW-03 PW-11 �. 'VY'05 ♦PW 22 Conpess'00 oaa,/ • PW?18 .PVVc2:1 s Figure 2. Reproduction of Potentiometric Surface in Shallow (<16m deep) Wells. Derived from Stantec, 2014, with modification by SLR (addition of yellow shade, and dashed yellow line, described in text above). Finally, the surficial sand (where present) and weathered till has been known to be the source of water for shallow dug wells. These are rare in this area, and none seem to exist downhill of the site. PW1 is 3.6 m deep, but is so productive it is likely tapping the Mackinaw where it is near surface. PW16 is 5.2 m deep, but has a 0.3 m bed of gravel providing the water. A shallow dug well also exists at PW03, but its source is unknown. These wells are in the Farewell watershed and are not downgradient of the site. PW16 is closest to the groundwater divide shown on Figure 1. If dewatering draws the water 3 Unfortunately PW13 is not shown on Figure 2, but is found south of Winchester Road, off the figure to the left. SLR 13 Municipality of Clarington Project No.: 209.40261.00000 Clarington Transformer Station Peer Review September, 2015 table down near the crest of the hill, there is a chance some laterally flowing water may be intercepted however it is unlikely groundwater divide would dissipate as recharge would continue to happen there. To test this conclusion, it will be important to compare their hydrographs (record of water level) against that for the site during dewatering, once they become available this autumn. In summary, from a well safety point of view we have concluded that no private wells are presently threatened by the construction or operation of the transformer station. 10.0 TRITIUM SAMPLING In August 2015, members of the EEA conducted some well sampling at PW1, PW2 and PW10 for the purpose of tritium testing. Tritium is a rare isotope of hydrogen, with a half-life of about 12.3 years. (That is, for example, a concentration of 100 Tritium Units (TU) would be reduced to half(50 TU) in 12.3 years.) Tritium is present in rain water and has been elevated since the 1950's when atmospheric testing of nuclear devices drove up the natural values (a maximum value of about 3000 TU was recorded in 1964). A record has been kept of atmospheric tritium since 1953, and provides a unique tool for the age dating of water. Tritium is not a contaminant, but due to its known rate of decay makes an excellent tracer for dating water. Although tritium from this source has dropped dramatically since this atmospheric testing was stopped in the early 1960's, levels still have not returned to background (pre- nuclear testing) levels and are around 14 TU. In recent decades, nuclear plants, which use lake water for cooling, have low levels of tritium release. This second source means that background levels will remain above pre-nuclear testing levels. Figure 3 shows the historic record of average annual values (shown in black) and current background levels (67 TU in 2012) from an OPG monitoring station 6 km from this site (shown in red). All data are publically available. 10000.0 Senest Senest -�IAEA Ottawa(annual avg,max.min) Precip m Clarington North 1000.0- i 100.0 � I I 100 _L7qV 1.0 l _ , . l l 4 1 1953 1958 1963 1968 1973 1978 1983 1988 1993 1998 2003 2008 2013 3H(TU) Figure 3. Atomospheric Tritium Concentrations with Time. SLR 14 Municipality of Clarington Project No.: 209.40261.00000 Clarington Transformer Station Peer Review September, 2015 The following values were measured from the wells by the EEA. The sampling protocols for these samples have not yet been reviewed, and our analysis assumes the results are valid. The sampling protocols were stipulated by the laboratory, the Andre E. Lalonde AMS Laboratory at the University of Ottawa. Table 1 below tabulates the results against the geologic horizon each well draws from. Table 1. Reported Tritium Concentrations, Enniskillen Environmental Association Well and depth Aquifer Tritium Concentration PW1 — 3.6 m deep Shallow dug well 47 TU mackinaw PW2 — 19 m deep Mackinaw 38 TU PW10 — 79 m deep Thorncliffe Aquifer 21 TU Given that the results were only just received, and that sampling protocols are not yet understood, only a preliminary assessment can be made at this point, assuming all things are at face value. The pathway to the deep aquifer can occur in two ways. First there is the vertical pathway, where the ground water moves about 0.05 m/yr downward. The water discharging to the Thorncliffe, some 75 m below the weathered till, would be 1,500 years old, and would have background concentrations of about 7 TU. The second pathway would be laterally from the ORM, some 6,000 m away. By working backwards to 1958 from a concentration of 21 TU in 2015, a source concentration would have to be 526 TU. The 1958 levels on Figure 3 above were about 500. The travel time would then be 57 years, giving an average linear ground water velocity of 6,000 m in 57 years, or 105 m/yr. This agrees remarkably well with the calculation of Thorncliffe travel times first presented to Clarington in December 2014 by SLR. There are many limitations to this calculation, and this conclusion has yet to be tested, however it is consistent with the observed conditions. By contrast, the concentration in the Mackinaw is almost twice as high at 38 TU, showing much more recent water. A similar calculation to that presented above for the vertical pathway to the 19 m depth in PW2 also shows the water should be near pre- 1950's levels and it is not. This implies lateral recharge with a near surficial source. Well PW1 is very productive but it is shallow. This is consistent with a shallow expression of the Mackinaw sand. The measured tritium of 47 TU in PW1 shows even more recent water. Using hydraulic conductivity values for the weathered till as measured by Stantec (3.7 x 10-7 m/s), a vertical downward gradient of 0.05 m/m and a porosity of 21%, a vertical downward average linear velocity of about 2.3 m/yr is calculated. Assuming a 2 year travel time, a source concentration of 53 TU may be back calculated. This is somewhat less than the 67 TU last measured in precipitation in 2012, however that location is 6 km south of the site and values should be lower further north from Lake Ontario. It can be concluded that this is indeed recent water, and consistent with a nearby recharge source. SLR 15 Municipality of Clarington Project No.: 209.40261.00000 Clarington Transformer Station Peer Review September, 2015 The preliminary implications of these results is that the deep Thorncliffe aquifer provides older water from the north and not from the site. The more shallow wells derive their water locally. This is consistent with the assumption made above that the sand on the east end of the site also is recharged locally. The tritium sampling conducted by the EEA has provided useful information. A more complete picture of the site itself could be made if tritium sampling were conducted in the onsite monitors as well. Here the Mackinaw is deeper and the water may be older. In addition it would be useful for the rotosonic work to proceed to allow tritium sampling of the aquitards. By waiting until construction is complete, the diffusion of tritium from the other boreholes that were drilled with tritiated water may with time cloud the results. In addition, it is expected that if the preliminary analysis bears out, that the aquitard tritium results will further support the case of site integrity. If they do not, then this is important to understand as well. 11.0 ADEQUACY OF THE MONITORING PROGRAM The current ground water monitoring program includes continuous water level recording (hourly) on all site groundwater monitors still in place, and in all private wells part of the current program. Water quality sampling is done quarterly on site and twice annually in private wells. There was early concern from the residents that the well water quality results were not representative of background pre-construction conditions. However, the water taken from these wells had an origin that predates the construction and can be considered background water quality and may be relied on. In particular well PW6 in the Thorncliffe aquifer had an initial measured benzo(a)pyrene concentration of 0.02 ug/L, very close to the detection limit, taken from the kitchen tap after water had passed through the home filtration system. Some of the shallow site wells also had measureable concentrations. Stantec reportedly revised their sampling protocols as they inferred that sampling materials may have introduced this. Subsequent sampling of the raw water in PW6, or the site wells did not repeat this result. Given the depth and source of the water from the Thorncliffe aquifer in PW6, the apparent lack of connection to the site, and the subsequent lack of measureable concentrations, it is reasonable to conclude that benzo(a)pyrene is not present in the groundwater. The well monitoring program being undertaken by Stantec on behalf of Hydro One is consistent with industry practice, and indeed is more inclusive than many in similar settings. SLR 16 Municipality of Clarington Project No.: 209.40261.00000 Clarington Transformer Station Peer Review September, 2015 We trust this report adequately summarizes our findings to date at the Clarington TS. Should you or any technical reviewer have any questions, please feel free to contact the Yours sincerely, SLR Consulting (Canada) �� '�' a o Steven Usher, WSc.IP.E ,P.G9;1,@GC , Senior Hydrogeologist 0"-"r R%0 undersigned. SU:sh SLR 17