From: Bill Avison

Sent: Mon Nov 20 12:40:24 2017

To: Gerald Fisher

Cc: Dan Zinder; Chaunee Seifried

Subject: Re: Avison Storm Rate Calcs

Importance: Normal

Attachments: VegetatedFilterStrips.pdf; Untitled attachment 12081.htm;

Thank you Gerald for working on this. I would like to offer a document for your consideration (attache PDF file) on “Vegetated Filter Strips”. These buffer areas that accept sheet water flow are being implemented in many municipalities including Oregon City. Please consider this as other City’s do, as a technique to reduce stormwater impacts and associated financial impacts to property owners. I clipped this information from Oregon City’s Stormwater standards.

Some stormwater LID techniques approved for use by property owners who live in Oregon City include:

• * Porous Pavement – Typically a walkable or drivable hard surface that looks similar to a traditional finish but allows water to infiltrate through the surface and into the underlying soil or drainage media.
• * Green Roof – A Green Roof is a lightweight vegetated roof system consisting of waterproofing material, a growing medium, and specially selected plants.
• * Flow through planter – A planter with an under drain system which is piped downstream. The planter holds some water but acts more like a filter.
• * Infiltration planters – Like a flow through planter minus the under drain. Infiltration planters need well drained soils.
• * Swales – Typically a long, narrow, gently sloping, landscaped depression that collects and conveys stormwater runoff. Usually swales include specially selected plants.
• * Rain gardens – Similar to a swale but larger with more specially selected plants.
• * Vegetated filter strips - Gently sloped areas designed to accept sheet (heavy water) flow. Filter strips are usually covered with grasses and groundcovers.

With the approval of these techniques, property owners can reduce the amount of impervious surface on their property, they can retain rainwater close to where it falls, and they can mimic natural drainage (filter) systems.

Attached is the detailed discussion on the "Vegetive Filter Strips”