FLOOD04125

• County: Statewide
• Basin: Statewide
• Title: Interim Procedures for Evaluating Scour at Bridges
• Date: 9/1/1988
• Prepared By: Federal Highway Administration
• Floodplain - Doc Type: Educational/Technical/Reference Information

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EXHIBIT V-A, 1 of 4

DEPARTIlEIT ""/DOT - OFFICE OF BRIDGES ANI)
STRUCTURES - Room 610

STATE OF "INNESOTA
OFFICE MEMORANDUM

TO: Rober-t Wolfe
Distr-ict Engineer

NTE. "ay 26, 1988

FROII: Don J. Fle_i ng
State Bridge Englne~

PHlIIE, 296-3172

SUBJECT: Distr-ict 2 Bridge Scour- Study

In the .ake of the Schoharie Cr-..k br-idge disaster- in HeM Vor-k,
the Office of Bridges and Str-uctur-es instituted a br-Idge scour-
scr-eening pr-ocess to deter-mine if ther-e .,.e potentially
hazar-daus br-idges in "innesata. The flr-st phase of this study
Involves the br-idg.. on tr-unk high..ays ov.,. _t.,._ys which
have been identified as being SUPPClf"ted on lIpt"ead Clf" unknCl\lllft
footings. Ten such str-uctur-es have been identified In Distr-ict
2. Of the ten br-idges, two _e scheduled fer r-eplac.-nt in
1'987 and 19BB and '''~e not analyzed. The Hydr-aullcs Section is
near-Ing ca~letion of the analysis of the r-...ining eight
br-idg_ (s.. attach--.t fClf" br-Idge nUlllber-s .nd location). On
June 7-9, a te.. fr-o. Hydr-aulics ..ill field review each of
th... bri dg...

The scour- anal ysi s has been conducted ac:ccrding to the
pr-ocedures set fcrth in the FHWA dr-aft Technical AdvisClf"Y on
the scOW'" at br-idg... Using th..e _thacfs, the analysis shaws
that ~t of the eight br-idg.s could exp.,.ienc. cr-itical scour-
conditions during high flo.... The dr-aft Techn1~.1 Advisory
r-eca..-nds that ..xisting br-idges ..ith cr-itical scour- potential
should be studi.d by an int.r-disclplin.,.y t... to evaluate the
effects of the scour- and d.termine the nec....,.y .itlgation
procedur...

A meeting is b.ing planned for June 30 in Ream 817 Centr-al
Office ..ith r-epr-esentativ.. fr-oa Foundations, Bridge Design,
Bridge eanstr-ucticm and ...intenance, Hydrilulics and Ui.tr-1i:t
p.,.sonnel ta dl.cu.. each af the .Ight br-idg... This
int~disciplinary te.. ..ill need to r-evi... each br-idge,
deter-_ine haw cr-itical the .cour patential is, the pr-iarity of
the br-Idge, and what _asur-es should be und.,.taken ta pr-ot.ect
the public and the br-Idge. The attached autline sho... what
..Ill be cav~ed at the...tlng. It i. anticipated that it ..Ill
take same ti.. ta cover each br-idge and the ...ting i. planned
far the entir-e day. In the event that not. aU br-idg.. are
cav~ed, ar th.t addition.l infor.atian is n-.ded, anath~
...ting ..ill be .cheduled. Thep~son(s) .ttending the ...ting
fr-oa the Di.tr-ict should be .oa.wh.t aquainted ..i th the
br-idge., their- pr-iar-ity ..ithin the di.trict, po..ib1e detour
r-out.. if it i. nec.......y ta close the br-idge dur-ing p~iad. of
flooding. .v.ilibility of personnel ta inspect .nd .antter the
br-idge, and the po..ibillty of scheduling c_tr-uctian of scour
caunt.,.....ur-...

B-17