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Central Temiskaming Area Municipal Groundwater Study (Town of New Liskeard, Town of Englehart, Township of Dymond, Township of Armstrong)

Executive Summary

Introduction

The Town of New Liskeard is the Study Lead of the Central Temiskaming Area Municipal Groundwater Study. Knight Piésold, of North Bay, Ontario and Water and Earth Science Associates (WESA), of Ottawa, Ontario, (KP/WESA) were contracted by the Study Lead to complete the Municipal Groundwater Study. This study conformed to the document Groundwater Studies 2001/2002, Technical Terms of Reference, (Ontario Ministry of the Environment, Nov 2001) hereafter referred to as the terms of reference. The study area for this Municipal Groundwater Study includes the Town of Englehart, located at the north end of the study area, the Town of New Liskeard, located at the south end of the study area, and the Townships of Dymond and Armstrong (Town of Earlton), located in between (Figure 1).

The objective of the Municipal Groundwater Study is to characterize the regional and local groundwater regime and to define wellhead protection areas. To define the wellhead protection area three hydrogeological aspects were considered. First it was necessary to characterize the aquifer from which the municipal well fields draw their groundwater. Second, the intrinsic susceptibility of that aquifer must be evaluated in terms of the potential for contaminant migration toward that aquifer. And third, an inventory of potential areas of contamination was catalogued and geo-referenced.

To ensure the concerns of interested stakeholders were addressed during this study, regular meetings were held with a steering committee.

Public involvement

KP/WESA encouraged public participation through the use of a website and public open houses.

Mapping

As required by the terms of reference, KP/WESA developed several maps as part of this study. Data for the mapping was obtained primarily from the Ontario provincial government databases. This information was supplemented by other published reports and documents.

Nine base maps were constructed for this project (bedrock and quaternary geology, topography, drainage, bedrock surface, overburden thickness, sand and gravel thickness, clay thickness, Regional Potentiometric Surface - Figures 2 to 10). The first four maps were generated using published data provided by the Ministry. The remaining five base maps were constructed based on data provided in the MOE Water Well Information System. Wherever possible, data validation was conducted following the requirements of the terms of reference.

Groundwater and Aquifer Characterization

The region known as the Central Temiskaming Area is located in the Temiskaming District of Northern Ontario at the head of Lake Temiskaming. The study area encompasses the aerial extent of an area known as the “Little Clay Belt”, or geologically as the lake Temiskaming Outlier.

The region just north of the study area (near Englehart) is underlain by a granite-greenstone formation. The bedrock bounding the east and west sides of the study area is comprised of sedimentary rocks. The bedrock in the center of the study area is comprised of dolostones, limestones, shales, and sandstones. The overburden, in order of oldest to youngest, include a basal diamicton (Figure 13), a glaciofluvial sand and gravel (Figure 14), and glaciolacustrine varved clay.

The regional groundwater flow system in the “Little Clay Belt” can be subdivided into two subsystems (Figure 15) that correlate well with the surface drainage patterns of the Wabi and Blanche River Valleys. Recharge of groundwater to the regional aquifers occurs along the bedrock ridge that separates the Wabi and the Blanche rivers where the overburden is thin, and along the edges of the clay belt. The direction of regional groundwater flow within the study area generally follows the path of the Wabi and Blanche river valleys (Figure 17).

The municipal well fields in New Liskeard, the Township of Dymond and Armstrong Township are located within the Wabi subsystem (Figure 16). The municipal wells in the Townships of Dymond and Armstrong are completed in the group of sedimentary rocks known as the Lake Temiskaming Paleozoic Outlier. The New Liskeard wells are completed in sand and gravel deposits underlying the lacustrine clays. The Englehart municipal well field is located within the Blanch drainage system. The municipal wells in Englehart are completed in an overburden aquifer made up of a thin (<10 m) sand and gravel deposit that is underlying a regionally thick (between 70 and 80 m) varved clay deposit that drapes the Blanch River drainage basin.

The municipal well field in New Liskeard appears to be extracting groundwater from a very transmissive overburden aquifer. The direction of groundwater flow in the vicinity of New Liskeard (Figure 18) is from the ridge located to the west, and at a gentler slope from the north, toward the south and Lake Temiskaming.

The two municipal wells in Dymond are completed in limestone that underlies about 32 m of clay. The direction of groundwater flow in this vicinity is from the northeast and east toward the southwest (Figure 18). Recharge to groundwater occurs along the bedrock ridge located east and northeast of Dymond.

The Town of Earlton is located very close to the hydraulic divide between the Wabi and Blanche Rivers. As shown on Figure 19, the direction of regional groundwater flow is from the east flowing toward Earlton. The recharge area for the Earlton municipal groundwater wells is therefore to the east, along the ridge. Whether groundwater flows toward the north or south from Earlton is difficult to determine as it appears to be at the groundwater divide.

The Town of Englehart is underlain by a thick, extensive layer of clay. At the location of the municipal wells there is approximately 60 m of clay overlying an extensive gravel aquifer. The regional direction of groundwater flow in this area is from the southwest and west toward the Blanche river valley (Figure 20).

Groundwater Intrinsic Susceptibility

The objective of defining GwIS is to identify areas where contamination of the groundwater is more, or less, likely to occur as a result of surface contamination. For this study, intrinsic susceptibility is assumed to be directly proportional to the product of the depth to the

aquifer and the hydraulic conductivity factor of the overlying materials. For each well location for which there was water elevation data, a value for intrinsic susceptibility was calculated by multiplying the depth to water by the Generic Representative Permeability Factor (Schedule C, MOE 2001). A surface was then created using the Krieging method (Figure 21). The higher the value the lower susceptibility. The results of determining GwIS for the study area clearly shows that most of the study area has very high GwIS (>80). This is due to the fact that most of the aquifers are confined, below a thick layer of clay. Lower values (<80) are generally found in regions where there are bedrock outcrops, along the edges of the Wabi and Blanche River Valleys.

Regional Contaminant Source Inventory

The purpose of this contaminant source inventory (CSI) was to identify past, present, and proposed activities that could pose a potential long-term risk to regional aquifers. The Ministry of Environment (MOE) provided existing data on potential contaminant sources in September 2002. During the week of November 11, 2002 members of the KP/WESA team conducted a regional field survey and inventory of potential contaminant sources. A total of 141 points of interest were noted and logged in the Regional CSI. Of the 141 points identified, 76 are located within the Well Head Protection Areas, or were rated as potentially being a high contaminant risk. These are all listed in Table 1.

Groundwater Use Assessment

To provide an overview of existing groundwater use within the study area, a groundwater use assessment was completed is to provide a baseline for further study and ensure a sustainable level of groundwater resource development. Data was collected from various sources including the municipality and MOE records, in addition, estimates were made based on land use in the area (residential, farming, etc). A summary of operations for each of the four municipal well fields is presented in Table 2. Pertinent permitted groundwater takings from within the study area are presented in Table 3. Any information already provided in Table 2 was not repeated in Table 3. Water Use Assessment based on agricultural water use as evaluated using 2001 census data combined with agricultural water use coefficients, population, known permitted water takings, and municipal water taking is shown in Table 4. Daily flow by month and total raw flow by month and year are presented in Tables 5 and 6 respectively.

Delineation of Groundwater Capture Areas

For this project, the numerical model MODFLOW was used to estimate groundwater capture zones. All numerical models involve a series of approximations and compromises, in the sense that they constitute a somewhat simplified representation of reality. Three hydrogeological units were included in the conceptual model, including from top to bottom (1) clay, (2) sand and gravel, and (3) shale and fractured limestone bedrock. The geometry of the hydrogeologic units was inferred from the MOE Well Records. The results of the modelling were plotted on potentiometric maps of the different municipalities in order to delineate each the capture zone around each of the municipal well field. The shape and orientation of the groundwater capture zones can thus likely be deemed representative of the actual conditions. However the precise location and size of the capture zones are simply estimates. Given the particular conditions of each area, a value judgement was made to determine the limits of the groundwater protection area.

The results of the modelling area shown in Figures 24 to 26 for the four municipalities. To compensate for uncertainties in the modelling, the width of the Well Head Protection area estimated from the modelling results

Municipal Well Head Protection Areas

The well head protection areas are plotted on the same figure as the intrinsic susceptibility and the location of the potential contaminant sources. The Figures 27 to 29 show that there are potential contaminant sources within all the WHPA for the four municipalities. Of greatest concern is the inner most WHPA representing a travel time of 0-2 year. The intrinsic susceptibility index within this first WHPA, for each of the four municipalities, is fairly high (>100). This means that the immediate area around the wells have a fairly high level of natural protection from contaminant impact. In New Liskeard and Earlton, the intrinsic susceptibility decreases to well below 100 within the second and/or third WHPA (2 to 10 year and 10 to 25 year travel time).

Zoning, provided by each of the municipalities, was plotted on Figures 30 to 32, along with the WHPA. These figures show that the WHPA encompass all types of land use (residential, commercial, industrial, parkland and institutional).

The synthesis of all the data collected during this study is summarised in the Land-Use Risk Rating figures (33 to 36). These figures show that all areas within the respective WHPA are either low or moderate risk.

Groundwater Source Protection Action Plan

The objective of a groundwater source protection action plan is to identify areas of greatest concern with respect to safe guarding the quality of a groundwater resource. The goal is to ensure a balance between the benefits of groundwater protection and potential impacts on economic and community development. Generally more stringent controls would be required close to the municipal well field, as well as in areas of greater sensitivity (lower GwIS). Land-Use Risk Rating generally takes into account time of travel to the well, intrinsic susceptibility, and the type of land use activities.

In the first zone, of greatest potential risk, the objective should be one of risk avoidance. It is within this zone that the greatest care must be taken to manage any current chemical use and handling practices and to minimize, or even avoid, the addition of moderate to high risk users

Management of land use within the second zone should reflect the principal of risk management. Occupants within this zone should be made aware that it has been estimated that their property lies within the WHPA, and that they should exercise care. Where high risk activities already exist, these establishments should be encouraged to implement best management practices and environmental management systems to ensure sustainable system operations.

Within the last designated well head protection area, the emphasis should be on education and training as a minimum. Any future development within this zone should be accompanied by a recommendation to implement best management practices to promote more responsible handling practices.