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HomeMy WebLinkAboutWD-51-84< r, U0 CORPORATION OF THE TOWN OF NEWCASTLE PUBLIC WORKS DEPARTMENT HAMPTON, ONTARIO LOB 1JO R. DUPUIS, P. ENG., DIRECTOR TEL. (416) 263.2231 987.5039 REPORT TO THE GENERAL PURPOSE AND ADMINISTRATION COMMITTEE MEETING OF MAY 22, 1984. REPORT NO.: WD -51 -84 SUBJECT: STORM WATER MANAGEMENT IN THE COURTICE URBAN AREA. RECOMMENDATION: It is respectfully recommended: 1. That this report be received; and, 2. That the Central Lake Ontario Conservation Authority ( CLOCA) be advised that after considerable review, the Town of Newcastle does not propose to adopt the specific requirements set out in the "Courtice Storm Water Management Study" in reviewing drainage for development proposals in the Courtice Area; and, 3. That CLOCA be advised that in depth consideration has been given to a follow -up implementation strategy for the recommendations of the "Courtice Storm Water Management Study" and it has been determined that such a proposal would be virtually impossible; and, ...2 t� t t�t R f R � 4 t�iJ" Page 2 REPORT NO. WD -51 -84 4. That CLOCA be advised that in the alternative, the Town will require development proposals in the Courtice Urban Area to conform to the general objectives relating to water quantity as expressed in the Courtice Storm Water Management Study, Pages 40 through 43, inclusive; and, 5. That CLOCA be advised that the Town will consider provisions for storm water quality in development proposals in the Courtice Urban Area only where such proposals are practice and can be easily maintained; and, (0 6. That CLOCA be provided with a copy of this report. BACKGROUND REPORT: In the mid 1970's, after definition of the Courtice Urban Area, various development proposals were put forward for consideration by the Town and other involved agencies. As these proposals were randomly located in Courtice, and the area was considered rather sensitive from an environmental point of view, studies of an environmental nature were initiated. One such study was the Courtice Storm Water Management Study. ...3 Page 3 REPORT NO. WD -51 -84 UI� The Courtice Storm Water Management Study was prepared for the Town under the guidance of a technical advisory committee. However, it must be pointed out that this was one of the first storm water management studies prepared in the Province at a time when the state of the art was in its infancy. Thus, the terms of reference for the study and the understanding of the technical advisory committee may have been somewhat idealistic, and not practical, from an implementation point of view. In fact, in recent discussions with the consultant who prepared the report, a caution was expressed that it should be considered as a guideline rather than gospel for storm water management in Courtice. Notwithstanding the above, the report and its recommendations were adopted by CLOCA and have been used rather stringently in reviewing development proposals. The Town, on the other hand, has never adopted the report but has alluded to it in area planning documents. On the Town's part, the report has been recognized as a guideline. Recently, development proposals in the area have again been activated, and in some cases detailed engineering is being prepared. Conflicting approaches between CLOCA and the Town have been taken with respect to storm water management, and several meetings of staff have been held in an attempt to resolve them. Because of this, staff have at least agreed that a common approach must be developed. ...4 Page 4 REPORT NO. WD -51 -84 Technical Difficulties with the Plan There are many difficulties with respect to interpretation of the recommended storm water management scheme and how it is to be implemented. Firstly, the recommended scheme, which utilizes very large trunk storm sewers and ponds, has a very high cost. Conservative estimates, in 1980 dollars, approximate $6.6 million. The Town is certainly in no position to up -front such costs nor are individual developers in a position to add their portion of such costs to the servicing charges associated with development. Other technical problems relate to the trunk storm sewers. These sewers are designed for storms with twenty -five year return frequency and accommodate, in some cases, more than one watershed. Thus, they are very deep, large and costly. As was experienced by the Town in the installation of a portion of trunk storm sewer west of Prestonvale Road last year, costs are high, wells can be dewatered and the capacity of the sewer itself is never likely to be achieved. Technology today has found that catchbasin lids will not pass enough water to even approach the twenty -five year capacity of the storm sewer. Ponds present a problem. In many cases they are proposed for location on lands not owned by a developer who wishes to proceed. Accordingly, acquisition and construction are a problem. Also, in many cases the proposed ponds are virtually inaccessible for maintenance. Related to maintenance, it is questionable whether the Town is in a financial position to provide the type of maintenance which would be required. ...5 Page 5 REPORT NO. WD -51 -84 These are only a few of the technical problems associated with the recommended plan for management of storm water in the Courtice area. The attached memo from the Director of Planning reiterates some of the concerns already expressed and presents other problems which would have to be addressed. A fairly comprehensive review of the matter has been undertaken and many more detailed concerns could be outlined, however, for brevity, only the major problems have been discussed. Objectives of the Study The general objectives of the study as outlined on Pages 40 through 43, inclusive, which are representative of storm water management philosophy in general can, for the most part, be accommodated without too much hardship on either the part of the Town or developers. Adhering to these objectives where possible will ensure that increased runoff to receiving streams is minimized during storms after development has occurred and thus problems with erosion will not be magnified. Accordingly, the Town should support such objectives in reviewing development plans. Water Quality The study makes recommendations to ensure that water quality in receiving streams such as the Farewell Creek is either maintained or improved. Ponds designed to hold back water from storms with up to a one - hundred year return frequency are proposed, with the intention that they retain sediment and allow for aeration of storm water before it is discharged into the creeks. In fact, the state of the art in water quality considerations is presently inconclusive and it is questionable whether the ponds will contribute to improved water quality. MWO Page 6 REPORT NO. WD -51 -84 f� Also, as pointed out by the Director of Planning, these ponds wil hold back runoff, allow it to increase in temperature and thus create an adverse effect on the receiving waters which are considered by CLOCA to be important cold water fisheries. Bearing all of these facts in mind, it is recommended that a requirement for comprehensive water quality provisions not be imposed upon development proposals. Implementation Plan As indicated previously there have been discussions between CLOCA and Town staff to attempt to reach common ground and compromises to attempt to accommodate the findings of the Courtice Storm Water Management Study. From such discussions it became apparent that if the intent of the study is to be covered out to the letter, there is a missing ingredient, in the form of an implementation plan. Such a plan would have to consider detailed engineering plans for each and every subdivision proposal, correlate them with each other, and formulate an implementation strategy for construction and financial contribution. Because development does not occur in an orderly fashion from downstream up, this would be impossible, imposing delays and /or financial hardships on individual development. Therefore, although an implementation strategy would ensure adherence to the specifics of the study, it would probably all but eliminate development in Courtice. ...7 Page 7 REPORT NO. WD -51 -84 Conclusion In short, although the intent of the Courtice Storm Water Management Study is valid, its specific requirements are very onerous, making development in the Courtice Area, virtually impossible. Recognizing this, and the desirability of some form of environmental protection in Courtice, the recommendations of this report are proposed. It is felt that they will very adequately address the matters of water quantity and erosion, and recognize the need to ensure reasonable water quality, but allow development to proceed. Resp 't fully sub pitted, ' — R.G. Dupuis, P. Eng., Director of Public Works. RGD:jco May 8, 1984. Attachment TOWN OF NEWCASTLE ra 1•R II TO: R. Dupuis, Director of Public Works FROM; T. T. Edwards, Director of Planning DATE: April 13, 1984 SUWECT: Courtice Storm Water Management Study File: PLN 16.1 APR 1 5 1984 TOWN OF NEWCASTLE PUB! !C WORKS DLPT. Further to our meeting of April 9, 1984, I offer the following comments in respect of the referenced study. In July of 1981 staff report P- 118 -81 was submitted to the then Public Works Committee. I attach a copy for your information. Unfortunately I have no record, on file, of how this report was dealt with. My reading of the report indicates that Planning staff supported either Alternative 1 or 2 since they would permit review of individual submissions and investigation of specific storm water management alternatives. This was premised on the desire to permit development to proceed without being constrained by plan5up- stream or-down-stream. I concur with these earlier comments, however, I believe that greater flexibility would be provided if we did not limit ourselves to one particular alternative. The study provides a number of recommendations (page 35 -38) which speak to intent and the underlying principles to be adhered to. I have the following comments in respect of these recommendations. i) Groundwater - The Gartner Lee study identified the ground water regime of Courtice as the single most predominant environmentally sensitive feature. The Storm Water Management study suggests that dewatering, associated with development, be localized or temporary. Available information indicates a perched watertable. Given this, it appears unlikely that dewatering can be localized unless construction is prevented from breaching the impervious clay levels. While this may be feasible in residential construction, the depth required for municipal ...2 R. Dupuis, Director of Public Works Page 2 services would certainly result in widespread dewatering unless extreme measures are taken by the developers. Such measures could however be costly and discourage development. ii) Existing Watercourses - Directly related to and to an extent dependant upon the groundwater are the Black R� Farwell Creek systems. Existing official plan policies and proposed zone regulations will protect these features. iii) Water Quality - This is of concern only insofar as sedimentation and coldwater fish habitat are concerned. Retention of tree cover in valley areas will assist in maintaining the water temperatures and minimize erosion. However, the study seems to place a greater emphasis on reducing sedimentation. While detention /retention ponds are effective they tend to raise water temperatures. On the other hand catch basins are not entirely effective in removing all sediments. The methods of controlling contaminants would require a great deal of effort by the Town and the results may not entirely justify the costs. iv) Erosion Hazard Zones: The underlying premise is zero change in runoff and rates. This point therefore speaks to existing problems and is not relevant to future development. V) Pond Construction and Operation Requirements - No objections are offered to the principle of detention /retention ponds, however, I share your concerns about maintenance and add my own with respect to public liability and safety. If privately owned and managed I have no objections. In summary, I believe that no one implementation alternative should be adopted. I would however, support adoption of the objectives recited on Page 40. All other guidelines, save and except those related to construction periods, should remain as guidelines for consideration in each instance without formal sanction. I hope these nts are of interest. T. T. Edwards, M.C.I.P. Director of Planning TTE /bb