Storfa Slope Failure and ResponseCity of Kalispell
Post Office Box 1997 - Kalispell, Montana 59903-1997 - Telephone (406)758-7000 Fax -
(406)758-7758
June 16, 2006
Ms. Susan Storfa
1373 Whitefish Stage
Kalispell, MT 59901
RE: Granary Ridge Environmental Consultation
Dear Ms. Storfa,
Thank you for your recent comments at a City Council meeting concerning the slope failure
behind your property just north of Granary Ridge development on Whitefish Stage Road.
We asked a consulting geotechnical engineer to evaluate this recent event. The report
indicated that there had been evidence of an earlier slip on your property. The engineer's
opinion is that the recent slump activity appears unrelated to the Granary Ridge
development and appears to be a continuation of the earlier slip. This is aggravated by local
high ground water that is flowing from the lower areas of the slope. High ground water is
causing a variety of problems throughout Kalispell. In addition, the area of the slip is one
where fill materials had been deposited in the past, likely during earlier construction on the
property. The engineer noted that the Granary Ridge developers have complied with the
recommendations made in the original geotechnical report. No adverse issues were
identified on the Granary Ridge property.
If I or my staff can be of further assistance, please do not hesitate to contact me at 758-7703.
Sincerely,
James H. Patrick
City Manager
Bette Albright, Street Tree Commission Chairman, thanked the Council for proclaiming April 28 as
Arbor Day. Albright noted the Arbor Day celebration will take place on the Russell School
playground where third graders will plant two commemorative trees.
Mark Lennon, DNRC Community Forester, in conjunction with the Arbor Day proclamation,
presented the City with the 2006 Tree City USA flag. Lennon remarked the City is receiving the Tree
City USA award for the 1.9th year in a row, and the Growth Award for the 13th year.
The main motion as amended carried unanimously upon vote.
C. STUDENT ISSUES
None.
Randy Hinzman, 80 Glacier Circle, spoke in support of Resolution 5113 authorizing the Community
Development Department to apply for a CDBG-ED grant.
Susan Storfa, 1373 Whitefish Stage, said she opposed the Granary Ridge development that was
approved last spring because of concerns with the density and the bluff. She said construction is
underway, with three houses being framed and the addition of yards and yards of gravel. Storfa said
Saturday night a major slough occurred on the bluff next to her house with yards of dirt and three
pine trees sliding down the hill. She asked who is responsible if her house or shop "goes down the
hill".
Rachel Martin, 1.05 Santa Fe Street, asked for an update on the flooding problem on her street. She
said the water has subsided somewhat, but residents continue to have water in their houses, and she
wants to know how the Council is going to fix the problem and when it will be fixed.
Mayor Kennedy responded the Council will be discussing stormwater problems during the work
session immediately following this meeting.
E. REPORTS RECOMMENDATIONS AND SUBSEQUENT COUNCIL ACTION
E/1. ORDINANCE 1573 —AIRPORT AFFECTED AREA — 2ND READING
Ordinance 1.573 adopts a set of regulations to protect the air space within 10,000 feet around the City
airport by regulating the height of structures and natural objects. Ordinance 1573 passed on first
reading April 3.
Larson moved second reading of Ordinance 1573, an ordinance establishing regulations in the
Kalispell City Airport Affected Area to provide airspace protection and land use compatibility
with airport operations at the Kalispell City Airport and declaring an effective date. The
motion was seconded.
Kalispell City Council Minutes
April 17, 2006
Page 2
James Patrick
From:
Jim Hansz Uhansz@kalispell.com]
Sent:
Monday, May 15, 2006 9:24 AM
To:
James Patrick
Cc:
fcastles @kalispell.com; Mark Crowley; sturner@kalispell.com
Subject:
FW: Granary Ridge Geotechnical Consultation Letter.
Attachments: 05-144 Granary Ridge Consultation Letter.pdf
05-144 Granary
Ridge Consultat...
Some time back we followed up on the slope failure just north of the Granary Ridge (GR)
development on Whitefish Stage Road. The concerns of the neighbor were that the GR
development had caused the problem. Attached is the geotechnical report for this recent
episode.
As indicated in the report, the original geotechnical report had identified evidence of an
earlier slip on the adjacent (complainant's) property and made note of it for the record.
The engineer's opinion is the recent slump activity appears unrelated to the GR
development and appears to be a continuation of the earlier slip. This is aggravated by
local high ground water that is flowing from the lower areas of the slope. High ground
water is causing a variety of problems throughout Kalispell. In addition, the area of the
slip is one where fill materials had been deposited in the past, likely during earlier
construction on the property (not Granary Ridge property).
Also, it should be noted that the GR developers have complied with the recommendations
made the original geotechnical report. No adverse issues were identified on the Granary
Ridge property.
After reading this report I believe the slip is most likely a continuation of slippage
caused by high ground water that is allowing an unstable fill slope north of Granary Ridge
to move. This movement will probably continue until the slope moves to a stable angle of
natural repose.
The City Council has expressed interest in this matter. I recommend sharing this with them
to keep them informed. I believe their approval of the Granary Ridge development was based
on sound engineering advice that was well documented in the original geotechnical report
and is further supported by this latest geotechnical investigation.
Jim Hansz
-----Original Message -----
From: Frank Castles [mailto:fcastles@kalispell.com]
Sent: Friday, May 12, 2006 11:08 AM
To: Jim Hansz
Cc: Susie Turner
Subject: Fw: Granary Ridge Geotechnical Consultation Letter.
Jim,
Attached is the geotech report regarding the recent slope failure just North of Granary
Ridge Subdivision on the East side of Whitefish Stage Road.
Frank
----- Original Message From: "Joshua Smith" <jsmith@cmgengineering.com>
To: <tklein@tkbuilders.us>
1
Cc: "Brett Walcheck" <brett@48-n.com>; <fcastles@kalispell.com>
Sent: Friday, May 12, 2006 8:20 AM
Subject: Granary Ridge Geotechnical Consultation Letter.
> Tom,
> Here is the letter regarding the recent slope activity to the north and
> east of the Granary Ridge Development. I have copied the City of
> Kalispell, 48 North, and Village Greens, as you requested. Please let
> me know if you have any questions.
> Joshua C. Smith, PE
> CMG Engineering, Inc.
> 406-257-8156
2
CMG Engineering, Inc.
P.O.Box 5159
1075 Trumbie Creek Rd., unit E
Kalispell, MT 59908-5159 --
Office:406-257-8156 �.F V
Fax:406-257-8179
http.,IM",cmgengineering.com
May 11, 2006
TK Builders
1st and Main Building
I' Street East, Suite 204
Kalispell, MT 59901
Subject: Geotechnical Consultation
Granary Ridge Development
Kalispell, Montana
CMG Project No.: 05-144
Dear Mr. Tom Klein,
At your request, CMG Engineering, Inc. (CMG) visited the site on April 18, 2006 for a meeting
regarding the stability of the slope to the north and east of the Granary Ridge Development in Kalispell,
Montana. The informal meeting was attended by representatives of the City of Kalispell, Village Greens,
the Developer, the Civil Engineer, and myself. Based on discussions with City of Kalispell representatives,
we understand the City of Kalispell received a phone call and a visit from the resident that shares the
property line along the north side of the Granary Ridge Development. We understand the resident is
concerned with some recent slope movement that occurred below the resident's house and below Lots 1 and
2 of the Granary Ridge Development, likely between April 14 and 16, 2006. At your request, CMG
Engineering, Inc. was asked to evaluate the recent- slope movement and provide a letter discussing the
evaluation. CMG returned to the site on April 26, 2006 for a more thorough evaluation of the slope
movement.
As indicated in the Geotechnical Investigation for the Granary Ridge Development, evidence of an
existing slump was present below the neighboring residence and Lots 1 and 2. In addition, the report
indicates that the slope in this area should be periodically monitored and regrading of this area may be
necessary if slumping continues to occur. The majority of the slope activity is to the east of the neighboring
residence and has been occurring for more than 15 years, as indicated by historical aerial photographs.
Observations also indicate that the slope below the residence to the north is steeper than the slope to the east
of the Granary Ridge Development, likely due to fill material placed on the slope during construction of the
neighboring residence.
CMG obtained measurements from the northeast Granary Ridge property corner to the top of the
recent slope activity using a clinometer and 100 ft tape measure on April 26, 2006. Comparing the recent
measurements to the elevation contours on the site plan for the Granary Ridge Developement, it appears the
slump on the hillside recently propagated to the west approximately 10 to 15 ft horizontally, and about 6 to
8 ii vertically. Observations of the area near the toe of the slope indicate significant groundwater seepage
is occurring through. the silty sand layers and likely contributed to saturating the toe of the oversteepened
CMG Enizineerina Inc
slope and resulted in the existing slump area being reactivated. It should be noted that the groundwater
seepage was observed flowing, approximately 5 gallons per minute and from a depth of about 45 to 55 ft
(vertically) below the crest of the slope, on April 26, 2006. In addition, CMG has observed. higher
groundwater levels throughout the Flathead Valley during March and April of this year, compared to the
recent past. In our opinion, the higher groundwater levels reactivated this historically active area.
Conversations with City of Kalispell representatives indicate the resident to the north of the Granary
Ridge Development is concerned that the recent development of Granary Ridge is affecting the stability of
the slope to the east of her house. At the time of the recent slope activity, the contractor had constructed the
utility lines and placed the basecourse for the roadway within the Granary Ridge Development. Construction
has also begun on three duplexes (Lots 1-2, 3-4, and 5-6). As recommended, in the Geotechnical
Investigation., fill material has not been placed near the slope with the exception of about 2 ft of fill material
in the vicinity of Lots 6 and 7. Utility lines were constructed in the roadways and not along the crest of the
slope to reduce the risk of water following pipe bedding and adding water to the slope. A storm drainage
system has been designed to collect roof water and outlet the water into a storage facility near Whitefish
Stage Road. The structures have been designed utilizing crawl spaces as opposed to concrete slabs -on -grade
to reduce the total weight of the construction near the crest of the slope. Setbacks have been established to
reduce the risk of increased loading on the relatively steep slope. In our opinion, the Granary Ridge
Development has not adversely affected the stability of the slope to the north and east. It appears the
existing slump below the neighboring residence is continuing to propagate to the west due to oversteepened
slopes from past failures and saturation of soils at the toe of the slope due to a relatively high groundwater
year.
We anticipate the slope activity in the vicinity of the historically active area will continue to
propagate to the west in response to high groundwater events, until a flatter, more stable slope angle is
obtained. Regrading the oversteepened slope, removing fill material from the slope below the property to
the north of the Granary Ridge Development, and providing adequate subsurface drainage at the toe of the
slope are all methods of reducing the risk of future slope movement.
Conversations with the attendees at the April, 18, 2006 niecting, indicate the slope activity is
occurring on Village Greens property, and property owned by Village Plaza, Inc. The Granary Ridge
Development owns a portion of the property on the slope to the east of the condominiums and south and
west of the recently active slope.
Please contact CMG Engineering, Inc., if you have any questions or concerns regarding this letter.
Sincerely,
Joshua C, Smith, PE John W. Ayers, PE
Senior Geotechnical Engineer Senior Materials Engineer
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