Township of Wentworth Municipal Spring

Transcription

1 Township of Wentworth Municipal Spring Catchment Area Perimeters of Protection Article 25 of the Groundwater Catchment Regulation Presentation to the Members of the Council November 22, 2007

2 Objectives of the Presentation Objectives of the Presentation 1) Hydrogeology 101 2) Municipal Spring Field Facts 3) Aquifer System Description 4) Catchment Area and Protection Perimeters 5) Conclusion 6) Recommendations

3 The Hydrogeologist s Common Technical Language Scientific Language Aquifer Type of aquifers Recharge/Infiltration Regulatory Language Catchment Area Perimeter of protection Vulnerability Conflict of Usage

4 The Two Principle Types of Aquifers The Two Principle Types of Aquifers Fractured Bedrock (Consolidated) Sand and Gravel (Unconsolidated)

5 Unconfined, Confined Aquifers and Natural Water Cycle Unconfined, Confined Aquifers and Natural Water Cycle

6 A Natural Resource that that is is Naturally Annually Renewed Case Case of of an an Unconfined Aquifer

7 A Natural Resource that is is Naturally Annually Renewed Case of of a Confined Aquifer

8 What Happens When a Well is Pumped What Happens When a Well is Pumped Regulatory Concept Regulatory Concept

9 What Does A Catchment Area Look Like in the Field? What Does A Catchment Area Look Like in the Field? Regulatory Concept Regulatory Concept Nappe phréatique aquifère Puits aquifère Puits Isochrone 200 jours Isochrone 550 jours

10 What is a Vulnerability Index? What is a Vulnerability Index? The groundwater vulnerability index reflects the level of risk of having the groundwater contaminated by human activities taking place at the surface. The DRASTIC method is commonly used to evaluate the Vulnerability Index.

11 Facts at The Municipal Spring Technical Characteristics Facts at The Municipal Spring Technical Characteristics 1) Elevation of the cover = m/msl 2) Depth = 1.55 m/top 3) Diameter = 0.91 meters 4) Water Level Depth (Low Waters) = 1.50 m/top 5) Water Level Elevation (Low Waters) = m/msl 6) Minimal Water Thickness in Spring = 0.05 meters 7) Feeding Point Elevation = m/msl 8) Difference in Altitude Between the Spring and the Feeding Point = 2.3 meters

12 Facts at The Municipal Spring Measured Flowrates Facts at The Municipal Spring Measured Flowrates 1. Measured Spring Flowrate : a) In April 2003 (reference 2) = L/min (12 usgpm) b) Section of the Water Intake = Totally Saturated 2. Estimated Mean Low Waters Flowrate : a) In September and October 2007 = 5.0 L/min (1.3 usgpm), b) Section of the Water Intake = Partially Saturated 3. Filling Flowrate : a) Variable : 0 L/min < Q Filling < 60 L/min (16 usgpm) b) Intermittent c) If Q Filling = 0 L/min : presence of an obstruction = probably air pocket d) Then the water levels in the spring raise e) When Water Height > Resistance of air pocket then instant emptying of the accumulated volume of water f) The Filling Flowrate : 30 L/min (8 usgpm) < Q Filling < 60 L/min (16 usgpm)

13 Octobre 1 to 13, 2007 Water Levels Fluctuations Octobre 1 to 13, 2007 Water Levels Fluctuations Source municipale - Période du 1 au 13 octobre 2007 Flucutation de la profondeur du niveau d'eau à la source Date et heure : : : : : : : : :00 0, : : : :00 0,25 Profondeur du niveau d'eau (m ) 0,50 0,75 1,00 1,25 1,50 1,75 Profondeurs enregistrées (m) Profondeurs mesurées (m) Prof. de la source = 1,55 m/pt rep. 2,00

14 Municipal Spring Watershed

15 Facts at The Municipal Spring Water Budget Facts at The Municipal Spring Water Budget Parameters Units Values Comments Watershed W idth meters 400 The W atershed is specific to the Municipal Spring and includes Length meters 300 only the area upstream of the Spring Surface meters Climatic Data Mean Annual Precipitation mm 1039,6 Normal, as per Mirable Airport Recharge rate % 12% Generally accepted for a till Mean Infiltration Rate Estimate Mean Annual Infiltration Rate m 3 /day 41,0 L/min 28,5 Municipal Spring Evaluation of the Water Budget Mean value that does not represent the extreme values associated to the Low and the High W aters Periods Low W aters Flowrate High W aters Flowrate Flowrates Measured at the Municipal Spring L/min 5,0 Mean Low W aters Flowrate Measured at the Spring (Fall 2007) L/min 45,4 Spring Flowrate Measured in April 2003 A mean infiltration rate of the snowpack and rain of 12% easily explains the flowrates - Low and High Waters - measured at the spring

16 Municipal Spring Catchment Areas and Perimeters of Protection

17 Facts at atthe the Municipal Spring Catchment Area Area and and Perimeters of of Protection Dimensions Parameters Units Flowrate (September 2006) Municipal Spring Flowrate m 3 /day 65,4 Catchment Area A = Stagnation Point m 11 B = Width at the Spring m 35 L = Maximal Width m 70 Perimeters of Protection Bacteriological (isochrone = 200 days) m 27 Virological (isochrone = 550 days) m 71 Unconfined Aquifer, Very Vulnerable (DRASTIC Index = 153)

18 Conclusions 1. The established perimeters of protection extend in an area where activities and works are likely to alter the microbiological quality of groundwater, for both the scientific perimeters of protection and the arbitrary radius, that is : a) The isochrones 200 days (bacteriological) and 550 days (virological) or b) The arbitrary radius of 100 m (bacteriological) et 200 m (virological) 2. The quality of the water supplied by the Municipal Spring is likely to be microbiologically altered or contaminated by any activity or works that potentially discharge microbiological contamination (septic tanks, leach fields) 3. The dimensions of the Immediate Protection Perimeter as set forth in Article 24 of the Groundwater Catchment regulation (GCR) can be reduced to 25 meters in the North axis, due to article 55 of the GCR, 4. The installation of a safety fence delineating the Immediate Protection Perimeter is not mandatory in the case of the Municipal Spring, because its average flowrate is smaller than 75 m3/day

19 Recommendations 1) Establish a plan by a land surveyor, locating the catchment area and both the scientific and arbitrary perimeters of protection related to the Municipal Spring as well as the lots concerned by these entities, in order to help choose the best solution as far as the perimeters of protection are concerned (scientific or arbitrary) 2) Evaluate with the legal advisor of the Municipality the impact of banning certain activities on the perimeters of protection (scientific and arbitrary) related to the Municipal Spring 3) Adopt a zoning regulation that will forbid: a) All activities within the immediate protection perimeter of the Municipal Spring, b) All activities and works likely to microbiologically contaminate the groundwater within the limits of the perimeters of protection (bacteriological and virological) selected by the Municipality