Tor FROM: SUBJECT: HOCKEY DEPARTMENT: SOIL REMOVAL SL-LAN AND SETTLING BASINS SC ke: FOR EXECUS ITCES FOR ONWARD TRANSMITTAL TO COUNCIL oe oa my So edteeee - ae te eee 2 BE This report is a summary of investigations carricd out by Mr. Ashford and two majer reports prepared by xr. J. tsun, PB. Eng., the professional cngineer who joined & mid-November. A. SETTLING BASINS The major cause of silt transportation from the Gravel Pit areas into the Coauitlam River is the fact that the Gravel Pit operators construct settling basins as part of the water courses flowing through their operations. & settling basin should allow the majority or all of the suspented sulids (mainly silts and clays) to settle cut before the water, in which they are suspended, escapes into a @rainage ditch or water course, The ideal conditicns for gcod settienont are low velocities and a long time perioe between entering the basin and leaving the basin. The longer the periog of settlement allowed, the greater the percent of Suspended sclids that will settle out What has been happening to the settling basins that ators have constructed in the water courses is that WS and velacities have negated the effect of the basins that have been obtained during low flows and @ low veiccities. The high velocities give rise to of the banks of the settling basins, with subsequent the settled solids, which are then carried down- It as the intention of this report to recommend that ng basins be constructed in the working areas such that rrablie flow in the creeks and other natural water courses does not affect the operation of settling basins. This will involve the construction of settiing basins adjacent to local WOrkK axeas within the Gravel Pit operations. No water from a gravel pit cperation or area should be allowed to enter the niturs) water course, which flows into the Coquitlam River, without it being filtered through a settling basin. -2- The construction and maintenance of the above-mentioned: settlement facilities should conform to plans and specifications prepared by a Professional Engineer registered wath the Asseciatioa of Professional Engineers of Gritish Colusbia, and these plans and specifications should be submitted as an integral part of the Gravel Removal Peraxrt Application. If the area of gravel pit operation is too small tc accommodate all the settling basins on the west side of Pipeline Road, then the processing of the silt and clay-laden waters would have to be accomplished, at least partially, on the easterly side of Pipeline Road. Tne necessity for this could easily be established at the time of permit applications when the plans of develepacnt are submitted. Part of the gravel pit operation requires that gravel be washed or cleancd to remove any silts or clays {such as that used as concrete aggregate). In this type of self-contained operation, the washing could be done by water recycled chrough a settling basin having no outlets to ditches or creeks. This method of washing ensures that no silt would reach natural water courses. BB. CONTROL OF CONTAMINATION OF CREEKS AND NATURAL WATER COURSES. According to a portion cf Subsection (b) of Section 6 of By-Law 1489: “all drainage facilities shall be kept free ef silt, clay, Sand, rubble, debris, gravel and any other thing originating from an excavation upon the lands and premises and causing obstruction to such drainage.” In other words, unless the silt, etc., causea obstruction to the drainage, there is no violation of the By-Law. According to Section 4 of By-Law 2041, Subsection (2) of action 6 of By-Law 1489 has been revised to: “no permit shall be issued 2f, in the opinion of the Engineering Supervisor, the proposed soil removal vould adversely affect any adjacent property, road, read allowcnce or water course. “ This appears to be outlining a required condition before isouance of a permit rather than a required condition during the term of the permit. It is suggested that Subsection (b} cf Section 6 of By-Law 1489 be revised: “All damage to municipal drainage facilities, roads or lanes or other municipally owned preperty resulting froa the excavation or the remaval of soil there-/rom shall be repaired, All water entering a drainage facility or natural watercourse shall be kept free of silt, clay, sancé, rubble, debris, gravel and