From: Brenda Reiner

Sent: Fri Mar 30 08:03:30 2018

To: 'Peter Burkoff'

Cc: 'george Snegirev'

Subject: 600 Rivers Lane

Importance: Normal

Peter and George:

As I mentioned earlier the City was working on standards for on site storm water treatment and detention. This is what we are using as design guidelines:

In the absence of application of building standards by the Clackamas County Building Department, the following requirements must be met in order for Public Works to allow for a drywell system to be installed due to insufficient capacity of the storm system on the north side of Toliver Road.

Drywell Requirements:

• * For bacterial protection, roof drains shall have at least five feet of vertical separation between the bottom of the drywell and the high seasonal water level.
• * Dry wells are considered underground injection control (UIC) devices.
• * Dry wells (UIC’s) shall be preceded by a City approved treatment devices or facilities. This includes treatment methods such as G2 type catch basins, swales, vegetated swales, wetlands, extended dry ponds and DEQ approved proprietary devices.
• * Drywells (UIC’s) shall be located to collect up to a maximum of one half acre of runoff.
• * Dry wells (UIC’s) shall be preceded by a City approved treatment devices or facilities. This includes treatment methods such as G2 type catch basins, swales, vegetated swales, wetlands, extended dry ponds and DEQ approved proprietary devices.
• * Dry wells (UIC’s) shall be designed and stamped by a professional engineer licensed in the State of Oregon. Design shall include a report with percolation test, groundwater depth, infiltration rate, and O&M plan.

If a drywell will not work on this property due to groundwater depth then the only other option available is for the builder to connect to the existing system. From our conversations, it sounds as if the storm system for the home will be lower than the system in the street. If this is the case then the builder may install a privately owned and maintained pumped system that can be connected to the back of the catch basin in front of 917 Toliver Road. The connection to the catch basin shall be core drilled only. No saw cut and break-in will be permitted. The connection will be by sanded collar and grouted on both sides.

Brenda Reiner | Senior Engineering Technician

City of Molalla

117 N Molalla Ave. | PO Box 248 |Molalla, OR 97038

Office: 503.759.0243 I Fax: 503.829.3676