HomeMy WebLinkAboutTimber Ridge Rockfall Mitigation 022610�
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T�ti�Jn �f ti'ail
r'�ttil: George Ruther
7� �atrth Fra��ta�e Rc�ac� ��est
Vail. Colc?rado 8165?
{�-uther�,��aiIgo1�. cu m)
Job No. 10�) 31 C1G
Subject: Rr�c:kfall Mitigation Alternative Selectran Informati�n, Proposed Vail
Timber Rid�;e Redevelnpment, i2�t) Nortl� Frantage Raad West, Vail,
Colarado
DEar l�!Ir. Ruther:
r�s requesteci, u�e are praviding ��relztninai-y cc}st and otl�er informatican tiaat lnay be
cUnsidered in your seleetion o� ro�kf�ll miti��tion alt�rnatives at tl�e subje�;t site in
accordance wifh our proposal to To���n of Vail datec�i Januar}� "?$, 2010. Hepwortl�-Pa��lak
Geotechnicdl, Inc. pi•evic�usiy cc��zducted a geoiogic site asses�ment and preliminary
roci�fall risk and �iutigatian study and presented our finciin�;s in a report dated Dece�nber
17, '?009, Job No. 109 3108.
Four opti���s to miti�aie the rockfall risk tc� the �arUject v�rer� presented in aur-pr�vic�us
repart. Option 1 is a wire rop� net b�rrier locatec� to th� sau.th of Lic�t�s Ridge L�ap at tl�e
back ofthe %uildings. Uption 2 is a��ire ro�e net l�arrier just t� tlie nortll of Lio��s Rid�e
Laop. Option 3 is a ��ire rc�pe rlet laarrier at the base ofthe autcrup st�rt -r.c>ne, and O��tion
� is an anchored steel me5h at the outcrc�p start zone, The tu1SE c��all for Optir�n 1, next ta
the buildiiags, has been eliminated by the To��n of Vai:i �nd l�as not been considered. A
t��aterial su�plier (�Geabru�g) and ai� installatiUn contr�ctor {i� enter) hatiEe been c;unsul#ecl
to obtain g�reliminary cost estirnates and installation fnetht�ds for the CRSP �0%
pr�bability level, as s�mmarized on Table 3 c�f o�ar De�einl�er �'?, 2009 report.
Tl�e sc�lection matrix for �eotechrtical facf:c�rs is presented in tl�e attached Table 1. [f a
CRSP 98°,�o probability leuel (Table 4 of our December i 7, 2004 re�ort) is selecteri, tlle
cost tar �ptiQn 1 wc�uld increase by �bout 25 ;�a and the cast for OptiUns ? and 3 w•ould
inerease ry about l 5°r'o. O�ation 4 cioes not ha�-e a prr�bability com�ouent. The AXI fcn��.
is self support�;d {essentiaily «rithc�ut harizontal restraintsj and the RXI Eence is restraitzed
witlz tie-baeks anci�ored in Yhe l�illsicie. There shouicl be nc�gligible Tnainter�ance costs ur�#il
a rockfall occurs, at that time tl�e rc���fall will need tc� be reina��et� anci the fence repaired.
Tlie rniti�;atit�n efiectiveness of Options 1; 2 a�1d 3 are considered the same for t11e
selected CRSP probabiIity ie�-e1 with �ption 4 being the niost effective.
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Town of Vail
Fe�bruary 26, �0�1{�
Page 2
if yc�u l�ave any questions oa• need fi.�rther assistanc�, please catl our aifrce.
SincereI}�,
HEP1�rORTH — P��'F, ' � �� �� � NIGAL INC.
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Attach��ent: G�otechnical Selection Matrix
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Job Nc�. It� 31UC �
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7ob No: 109 310C
Table 1
Geotechnical Selection Matrix
Vail Timber Ridge Rockfall Mitigation
Option Barrier Height Length Installation Material Installation Total
T e Method Cost Cost Cost
1 AXI IS ft 900' Automated $130/ft $100/ft $21dk
2 RXI 11 ft 990' Part $1801ft $ZQOIft $380k
Automated
3 RXT 10 ft 1060' Airlift/ $165/ft $400/ft $600k
Hand
4 TECCO N/A 1J3,220 Airlift/ $2.25/sf $3.50/sf $650k
Nettin sf Hand
Notes:
1)
2}
3)
4}
5)
Based on CRSP 90°/a probability level
Costs are for feasibility relative comparisons only
Maintenance costs not included
No access trails are assumed for all options
All barriers and netting are colored