Delineation of a Fuel Spill Related Intake Protection Zone 3(IPZ-3) for the Stoney Point Drinking Water Intake Extending up the Thames River Watershed

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1 Draft Technical Memo: Delineation of a Fuel Spill Related Intake Protection Zone 3(IPZ-3) for the Stoney Point Drinking Water Intake Extending up the Thames River Watershed Author: Jason Wintermute, Lower Thames Valley Conservation Authority Date: January 31, 2014 Background There are three drinking water intakes on the Canadian side of Lake St. Clair; Windsor, Belle River and Stoney Point. All three of these intakes are located in the jurisdiction of the Essex Region Source Protection Authority (ER SPA). The Essex Region Source Protection Committee (ER SPC) has decided their intakes require additional protection beyond that provided by IPZ-1s and IPZ-2s policies and is delineating IPZ-3s related to fuel spills. In a report by Baird (Baird 2011a) modelling showed that particles in the lake at the mouth of the Thames River were reaching the intakes at Windsor, Belle River and Stoney Point. The ER SPA consulted Thames Sydenham and Region Source Protection Region (TSR SPR) staff and asked for candidate locations on the Thames River and its tributaries which could be used for further event based modelling to determine how far an IPZ-3 may extend into the Lower Thames Valley Source Protection Authority (LTV SPA). The modelling (Baird 2011b) showed that benzene from the fuel spills (2% benzene by mass) upstream in the Thames River watershed could reach the Stoney Point and Belle River intakes at concentrations exceeding the Ontario Drinking Water Quality Standard (ODWQS) of mg/l. This would be considered a deterioration of the water for use as a source of drinking water for the intake and consequently could be considered a significant drinking water threat. The LTV SPA Assessment Report (AR) currently does not include any IPZ-3s and therefore there are no Policies in the TSR Source Protection Plan to address such significant threats in the LTV SPA. As it stands now, the ER AR will show fuel related IPZ-3s that terminate at their jurisdictional boundary with indications that the IPZ-3 should extend further into the LTV SPA and that there are possibly significant threats located there. This document is being prepared to provide the TSR SPC with information to allow it to determine how the TSR should address this cross boundary issue. Previous Work by Baird & Associates Generally speaking, the methodology used by Baird was to divide the modelling into two parts. Modelling in the Thames River and its tributaries, from the spill to the mouth of the Thames River, was conducted using longitudinal dispersion methods

2 following MOE guidance (MOE 2009b). From the mouth to the intakes, Baird used their proprietary MISED model for in-lake modelling. The Microsoft Excel spreadsheets used by Baird for the longitudinal dispersion portion were provided to the TSR SPR. The Technical Rules (MOE 2009a) specify that an event with a return period of up to 100 years can be used for IPZ-3 delineation. Baird conducted a joint probability analysis (Baird 2011a) to define wind and tributary flow events with the required return period. Two events were selected from that study for use in the Thames River watershed work (Baird 2011b). In both cases, the event consisted of a mean flow in the tributaries occurring during a 10-year return period wind. As flow monitoring is not conducted on any of the Thames River tributaries downstream of Chatham, flow data from the Ruscom River (Water Survey of Canada Station 02GH002) was scaled based on watershed area to estimate mean flows in the tributaries. A summary of the flows and watershed areas used in the analysis are found in the Appendix Table 2. Flows for the Thames River were taken from Water Survey of Canada Station 02GE003. Watercourse widths and lengths were estimated using satellite imagery found on Google Earth (Baird 2011b). Flow velocities were calculated using Manning s formula assuming that the flow is constant along the reach and assuming a roughness coefficient of Energy slopes for Manning s formula were assumed to be equal to the topography slope and were measured using the Ontario Digital Elevation Model (DEM). The depths of the watercourses were solved for using the estimated mean flow, velocities and width. Longitudinal dispersion coefficients were calculated as an average the methods described in the MOE guidance (MOE 2009b). Initial work on IPZ-3 delineation for the Lake St. Clair intakes (Baird 2011a) had involved event based modelling for fuel tanker spills of 34,000 L at road crossings. Consequently, when looking to examine spill locations in the LTV SPA, the candidate locations chosen were also transportation related. The three candidate locations chosen were: 1) the first bridge crossing over the Thames River 11.2 km upstream from the lake at Jacob Road, 2) the Highway 401 crossing of Baptiste Creek 6.8 km upstream from the lake, and 3) a railway crossing of Big Creek 1.5 km upstream of the lake. See Appendix Figure 1 for the locations. For the road crossings, 34,000 L gasoline tanker truck spills were modelled and for the railway crossing a 68,000 L rail tanker spill was modelled. The modelling showed that benzene from the fuel spills upstream in the Thames River watershed could reach the Stoney Point and Belle River intakes at concentrations exceeding the Ontario Drinking Water Quality Standard (ODWQS) of mg/l. Results of the modelling were provided in a memorandum (Baird 2011b) and can be found in the Appendix Table 1. Since Baird provided their spreadsheets to the TSR SPR, staff were able to review the calculations. Due to a poorly chosen energy/topographic slope, the depth of the Thames River in the downstream reach was calculated as somewhere between 0.5 and 0.66 of a metre deep in the spreadsheet. The actual depths are in the 4.5 to 6

3 meter range. While the error was easily corrected using actual gauge data, and the spreadsheets have been extremely useful in allowing the TSR SPR to move forward with this IPZ-3 delineation, that error essentially invalidated any conclusions that could be drawn from the report (Baird 2011b) regarding what distances upstream a spill would have to occur to create a particular benzene concentration at the mouth of the Thames. This error in no way affected the in-lake work conducted using the MISED model. Subsequent to that work being undertaken, the ER SPC looked at the concentrations arriving at their intakes and decided that the volume of the spills could be reduced and still have exceedances of the ODWQS at the intakes. Through consultation with Baird and Stantec, the size of spills which could produce a significant drinking water threat was reduced to 15,000 L (Stantec 2011). Determination of Concentration Criteria at the Mouth of the Thames In order to combine the results of the in-lake MISED modelling with longitudinal dispersion modelling, the concentration of benzene at the mouth of the Thames which would produce the ODWQS of mg/l at the intakes was required. Given that information, longitudinal dispersion modelling was then used to determine the maximum distance upstream for the IPZ-3. Of the scenarios modelled by Baird (Baird 2011b), Scenario 9 for the Stoney Point intake produced the highest benzene concentrations at an intake. (Table 1). Intuitively this should produce the IPZ-3 extending the furthest upstream in the watershed. The relationship between concentration at the mouth and concentration at the Stoney Point intake for Scenario 9 was therefore graphed to attempt to determine what concentration at the mouth would produce the ODWQS. (Figure 2). Although 3 spill locations were modelled, 2 of those spills produced the same concentration at the mouth of the Thames River. That left only 2 data points for which to extrapolate behaviour that may occur from the mouth to the intake. Figure 2 shows just two of the alternate behaviours that could exist; linear and logarithmic. Trying to extrapolate these lines significantly lower than the 0.49 mg/l data point introduces quite a bit of uncertainty. A logarithmic model is more realistic than other models as it allow for the situation where a small spill at the intake can produce a negligible concentration at the intake. A logarithmic model suggests that the ODWQS would be observed at the intake with 0.19 mg/l (rounded to 0.2) at the mouth. Spill Modelling in the Thames River and Tributaries Once the criterion benzene concentration at the mouth of the Thames was obtained, longitudinal dispersion modelling was conducted to determine how large of a spill and how far upstream it would have had to occur in order to meet that criterion at the mouth and consequently create an exceedance of the ODQWS at the Stoney Point intake.

4 Since the existing Baird reports examined a 34,000 L spill and the ER SPA is using a 15,000 L spill for their IPZ-3, these two spill volumes were analyzed. These volumes represent typical volumes carried in large and small tank trucks and are also consistent with volumes considered elsewhere in the Thames-Sydenham and Region. The actual longitudinal dispersion modelling was conducted using the spreadsheets provided by Baird and therefore the methodology was the same. (Baird 2011a and 2011b). The data going into the calculations was likely slightly more accurate as additional information was available to TSR SPR staff such as the Southwestern Ontario Othrophotography Project (SWOOP) aerial photography from 2010, additional elevation data and contour lines for elevations, updated drainage network lines from the relevant municipalities, and better defined subwatershed areas using catchments defined by the Ministry of Natural Resources (MNR) Water Resources Information Program (WRIP) using ArcHydro. The results of the longitudinal dispersion modelling for 15,000 and 34,000 L spills can be found in Tables 3 and 4 respectively. The shaded rows indicate locations that were used to derive IP-3 extents. The locations modelled can be seen in Figure 4. The 15,000 L spill modelling indicated that the IPZ-3 would remain very close to the mouth of the Thames River. It would not reach up the Thames as far as Jeannettes Creek and would extend up Big Creek to just past the confluence of Baptiste Creek. The 34,000 L spill would produce a substantially larger IPZ-3, extending up the Thames River a couple of kilometers past the bridge over the Thames River at Jacob Road. It would take in the entire Big Creek watershed and would extend about 7.5 km upstream on Jeannettes Creek. There is a pond-like area on Jeannettes Creek around location where the upstream extent should fall, so the pond itself became the upstream extent. Delineation of IPZ-3s According to the Technical Rules Part VI.5 68 and 69(MOE 2009a), an IPZ-3 delineation will cover 1) the area within each surface water body through which, modelling demonstrates, contaminants released during an extreme event may be transported to the intake; 2) where the area delineated abuts land, a setback of not more than 120 metres inland along the abutted land measured from the high water mark of the surface water body that encompasses the area where overland flow drains into the surface water body; and 3) the area of the Regulation Limit along the abutted land. However, the area delineated shall not exceed the area within each surface water body that may contribute water to the intake during or as a result of an extreme event. The IPZ-3 area covering the surface water of the Thames River and tributaries was delineated using the longitudinal dispersion modelling. The area at the mouth of the Thames River is covered by a very large flood prone Regulated Area. However, the area is also heavily dyked and pumped. The presence of dykes means the inland portion of the IPZ-3 does not extend the full 120 m but rather terminates at the

5 dyke. Most of this land behind the dykes is also behind the pump systems. Longitudinal dispersion modelling indicated that the IPZ-3 would not extend into the pump systems. Consequently, most of the large Regulated Area is excluded from the IPZ-3. Given that the land is still very flat but unprotected by dykes outside of the Regulated Area, the full 120m setback from the watercourse along the abutted land was used. The area in Lake St. Clair was determined by simply drawing a smooth line from the IPZ-3 delineated by the ER SPA to the IPZ-3 around the Thames River to include the water between the mouth of the Thames River where the modelled spills enter Lake St Clair to the IPZ-3 delineated by Baird. Additional in water modelling would be required to determine if areas further along the lakeshore should be included. Additional wind and flow scenarios would have to be considered to adequately assess the extent along the lakeshore and whether additional watercourses should be assessed. Additional in-lake modelling is beyond the scope of this project, but could be considered in the future. Delineations for the IPZ-3 based on 15,000 L and 34,000 L spills can be seen in Figure 3. Uncertainty The uncertainty in these delineations comes from a variety of sources. There is inherent uncertainty from the use of the MISED numerical model for the in-lake analysis. This uncertainty was considered as part of the work undertaken by Baird and similarly affects this project. There is uncertainty in the use of the longitudinal dispersion modelling, which was also discussed in the work undertaken by Baird. Although the estimation of parameters was improved from the Baird work through the use of improved data sets, as discussed earlier in this report, this would result in only a modest reduction in the uncertainty associated with this part of the analysis. There is an increased uncertainty in the way a criterion benzene concentration was chosen at the mouth of the Thames to couple the longitudinal dispersion modelling to the MISED model. Although there are assessments of the uncertainty for the MISED model and the longitudinal dispersion method provided in the previous Baird reports (Baird 2010, 2011a, 2011b). There are a few worth highlighting here. With the in-lake MISED model, a limited number of spills and 100 year joint probability wind/flow events were considered. There are numerous other scenarios which could be modelled that would result in different concentrations at the intake. It is possible that other scenarios could result in different (higher or lower) concentrations at the intake. The longitudinal dispersion analysis is a very simplistic approach. The method was designed for open flow, not pumped systems. Approximations for pumping operations had to be made to suite the method. Data going into the models were also derived rather than measured in the field, such as flow and channel cross sections. Dispersion within the channel is largely controlled by a dispersion coefficient and while six methods of determining that value were provided in the

6 MOE guidance (MOE 2009b) a simple average of the six methods was used rather than trying to assess the methods to determine which may be more appropriate. The uncertainty in determining the way a criterion benzene concentration was chosen at the mouth of the Thames to couple the longitudinal dispersion modelling to the MISED model is another factor. Attempting to extrapolate an unknown mathematical relationship from only 2 known data points introduces a high degree of uncertainty. In terms of the actual mapping, the upstream portions of the IPZ-3 depend on having an accurately digitized drainage network. As drainage linework in the Lower Thames is several years out of date and was never checked for quality control. As such there could be missing or incorrectly placed lines. Such a situation would be easily determined by a site visit from a Risk Management Official. In assigning a qualitative description to the level of uncertainty for this delineation, it would be most appropriate to consider that the result has a high level of uncertainty. This level of uncertainty is consistent with the uncertainty associated with the delineation of IPZ-3 in other areas as the methodologies employed are similar. It has been established through the guidance provided by the province that this level of uncertainty is appropriate for the intended purpose of delineating an IPZ-3. Expansion of the IPZ-3 The Technical Advisory Committee had inquired whether the IPZ-3 should be expanded further north up the Lake St. Clair shoreline towards and including the McFarlane Relief Drain and the Rivard Drain and Pump Works. The drainage systems between the current IPZ-3 delineation and the Rivard/McFarlane are primary for coastal wetlands. Based on this current work it seems unlikely that the Rivard/McFarlane drainage system behind the pump works would be included in the IPZ-3, however as noted earlier additional in-lake modelling would be required to adequately assess this. References Baird, In-water IPZ-2 Delineation for Essex Region and Chatham-Kent Intakes Phase II Studies. A report prepared for ERCA and Chatham-Kent by Baird as sub-consultant to Stantec Consulting Ltd. Baird, 2011a. IPZ-3 Delineation for ERCA Source Water Studies Stoney Point, Belle River, and Windsor Intakes. A Report Prepared for the Essex Source Protection Region. Baird, 2011b. Re: Thames River Spill Modelling in Support of Source Water Protection. Memorandum to Girish Sankar, SCRCA, Dated August 3, 2011.

7 MOE, 2009a. Technical Rules: Assessment Report. Clean Water Act, Amended on November 16, MOE, 2009b. Technical Bulletin: Delineation of Intake Protection Zone 3 Using Event Based Approach (EBA). Dated July Stantec, Essex Region Source Protection Planning Technical Study: IPZ-3 Delineation, Vulnerability Scoring, Threats Analysis and Uncertainty Level Assessment for the A.H. Weeks, Lakeshore and Stoney Point Water Treatment Plants. April 2011.

8 Appendices Table 1: Predicted Peak Benzene Concentrations at Intakes (Baird 2011b) Spill Location Distance from Mouth of Thames River (km) Spill Volume (L) Event Peak Benzene Concentration at Thames River Mouth (mg/l) Event Event Peak Benzene Concentration at Intake (mg/l) Stoney Point Belle River Baptiste ,000 L 0.49 Scenario Creek Scenario Not detected Thames ,000 L 0.49 Scenario River Scenario Not detected Big Creek , 000 L 3.35 Scenario Scenario Not detected Table 2: Watershed Areas and Estimated Mean Flows in Tributaries Tributary Watershed Area (km 2 ) Mean Flow (m 3 /s) Ruscom River Baptiste Creek Big Creek (before Baptiste) Big Creek (after Baptiste) Jeannettes Creek Thames River NA 60.1 Total Flow to Lake St. Clair NA 70.3 Big Creek (before Trembley) Trembley Creek West Branch Big Creek East Branch Big Creek West Branch of Big Creek (before W. Ogle) West Ogle Drain Forbes Internal Drain Jeannettes Creek (before of Forbes) Bradley Pump Works

9 Table 3: Predicted Peak Benzene Concentration at Thames River Mouth (15,000 L Spill) # Spill Location Distance from Mouth of Thames River (km) Event Peak Benzene Concentration at Thames River Mouth (mg/l) 1 Big Creek (at Rail Line) Big Creek (at Baptiste Creek) Big Creek (250 m upstream of Baptiste Creek) Baptiste Creek (at Highway 401) Thames River (at Jacob Road Bridge) Thames River (1 km upstream of Big Creek) Bradley Pump Works # refers to location in Figure 4 Table 4: Predicted Peak Benzene Concentration at Thames River Mouth (34,000 L Spill) # Spill Location Distance from Mouth of Thames River (km) Event Peak Benzene Concentration at Thames River Mouth (mg/l) 1 Big Creek (at Rail Line)(68,000 L) (1.143) 4 Baptiste Creek (at Highway 401) Thames River (at Jacob Road Bridge) Big Creek (at Leamington border) West Ogle Drain (headwaters) Thames River (2 km upstream of Jacob Road Bridge) Jeannettes Creek (at Forbes Internal Drain) Jeannettes Creek (at Farmer Internal Drain) Bradley Pump Works # refers to location in Figure 4

10 Figure 1: Potential Spill Locations in the Thames Watershed modelled by Baird Figure 2: Concentrations at Thames River Mouth and Stoney Point Intake Concentration at Intake (mg/l) Stoney Point Intake, Scenario Logarithmic 0.4 Linear Concentration at Mouth (mg/l)

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