Burnham to Evergreen Sewer/Cottonwood Proposed Sewer SytemPublic Works Department
Po-,[ 01'I1cc Box 1997. Kalispell. Moniana 59903-1997 - Telephone (406) 7-58-7720. Fax (406) 755-7831
May 11, 2009
Ms. Roberta Struck
Flathead County Sewer District #1
130 Nicholson Drive
Kalispell, Montana 59901
Re: Proposed Sewer System in Cottonwood Estates
Dear Roberta:
The City of Kalispell received a request to consider the E/ONE sewer system as an
alternative to a standard sewer system in the proposed Cottonwood Estates Subdivision.
While the E/ONE appears to be a well -functioning system, this is not an appropriate
application for this system.
The City of Kalispell manages a centralized sewer system of gravity mains, lift stations,
force mains, and a wastewater treatment plant. The City has allowed the E/ONE system to
be used in Iimited applications, where an existing adjacent gravity main is available for
direct connection. In the case of Cottonwood Estates, a gravity main is not available and
the E/ONE force main would be required to extend approximately one -quarter mile in a
public right-of-way before discharging. This force main would parallel an existing effluent
main owned on operated by the Flathead County Sewer District # 1. The City plans for and
operates sewer mains that have capacity for existing and future development. This varies
from the piecemeal approach of adding parallel lines to smaller areas of the system.
The City of Kalispell owns and operates gravity lines and lift stations within areas of high -
groundwater. These systems can be constructed to eliminate or decrease groundwater
infiltration. The lift stations provide a single point of operation and maintenance. The
proposed E/ONE system would have 91 points of operation and maintenance.
Lift stations within the City have automatic backup power in case of electrical power
failure. Diesel or natural gas generators with transfer switches provide this backup power.
The E/ONE system does not have centralized backup power and is subject to failure in the
event electrical power becomes unavailable.
The City requires developers to install sewer utilities for an entire development. This allows
the City oversight of the entire utility construction. Cottonwood Estates proposes to install
a portion of the E/ONE system (force main and services only), but abdicates the purchase
and installation of individual grinder pumps to each homeowner. This approach results in
varying quality of workmanship by multiple contractors and homeowners. This is not the
nature of a public utility.
The preliminary design and engineering for Cottonwood Estates includes the addition of
another 91 tots to the south of the proposed 91 lots. The proposed E/ONE system.
(specifically, the force main in Helena Flats Road) was designed to handle these additional
flows, but does not account for other future development. The City does not take this
approach to new infrastructure; new infrastructure must account for a larger planned fixture
development area. This large -picture approach allows additional development to utilize the
existing system. This eliminates the addition of unnecessary improvements that create
added costs and demands to the system operators.
The City does not recommend the use of the proposed system in this application. The City
recommends the elimination of basements in this area and the installation of shallower
gravity mains and a single lift station in the eastern portion of the development. The City
also recommends that the developer size the force main to accommodate flows from a larger
development area. There are various methods to allow for a larger force main during initial
low flow conditions. Please call me if you have any questions regarding this
recommendation.
Sincerely,
Paul E. Burnham, P.E.
Assistant City Engineer
cc: Tom Cowan, Carver Engineering, 1995 3`d Avenue East, Kalispell, MT 59901