12/19/2001 Env Bd Packet - Laserfiche WebLink

Home Search

Ind infarmation. In London Grove Township. Pennsylvania. for example. the stormwater plan contains an analysis of stormwater flow. thermal im- pacts, runoff quality, erosion and sedimenta- tion, and groundwater recharge. It further contains a delineation of the outcrop area of Cockeysville Marble, a high yielding aquifer that is vulnerable to groundwater contami- nation. The selection of management prac- tices considers the origins of stormwater (di- vided into three harmfulness classes) and the classifications of streams in the township as cold water fishery streams, some with 'exceptional value," and others as trout stocking streams. Setting standards Municipalities have the legal authority to set standards that relate to public health, safety, and environmental quality. Standards are numerical thresholds that separate ac- ceptable and unacdeptable impacts. A stan- dard that most municipalities have in their books is that pre - development runoff peak flows not exceed post - developme ...peak flows. In order to rotect str „a,� a re- source, sere n- dar or the concerns described above. A stormwater management ordinance Stormwater management requirements are often part of the subdivision regulations of a municipality where, together with erosion and sediment control, they take up but a few pages. In order to achieve clean stream goals, stormwater management should be addressed through a separate ordinance that iparian Forest Buffer Riparian Forest Bider Figure 6. The "wooded riparian forest buffer" shades the headwater stream and keeps it cool. Concentrated storm flows are reconverted to sheet flow through a level spreader and infiltrated in part before they reach the stream. relates to, and implements, the stormwater plan. It should contain a statement of find- ings, explain its legal base, and set forth de- sign standards and criteria. The ordinance should come into play whenever a change in land use is being sought, giving the de- veloper a comprehensive set of stormwater management requirements, management measures, and design standards and criteria. Before development can commence, the de- veloper should be required to make a plan submission that follows a defined format and is subject to a review and approval process. Such a process should permit inter- action between parties, and, if necessary, for modifications to be made to the plan. There should be defined permit requirements and procedures including guidelines for fees, a Attenuation at Seduce Prior to Colneatratlen Coneeyaane Pre - Treatment b Contention for Peak Central V Extended Detention/ Dententlee ter Quality Centred Infiltration ter Northam' ry lemaet Mitigation le... Temp raiIre Cantrell Maintenance Figure 7. Components of a stormwater management system. JANUARY — FEBRUARY 1994 19