Attachment M - Design Memo MCDD USACE 1957.pdf

I

DESIGN MEMORANDUM

MULTNOMAH COUNTY

DRAINAGE DISTRICT NO. I

LOWER COLUMBIA RIVER ,

IMPROVEMENT TO EXISTING WORKS

OREGON AND WASHINGTON

Prepared by U. S. Army Engineer District, Portland

Corps of Engineers 30 Apri I 1957

Attachment M

,j

Design Memorandum

MULTNOMAH COUNTY DRAINAGE DISTRICT NO. 1

Lower Columbia River Improvement to Existing Works

Oregon and Washington

1/ II

_)o ""\

Prepared by U. S. Army Engineer District, Portland

Corps of Engineers 30 April 1957 l PertJncnt data

2 Project authorization

3 Investigations

1+ Local cooperation and vl.ews

~ Location of project and tributary area

G Project plan

7 Departures from project document plan

8 Hydrology

9 Geology

10 Other plans investigated

11 Description of proposed structures and improvements

12 Sources of construction materials

13 Real estate requirements

14 Relocations

15 Cost estimates

16 Schedules for design and construction

17 Operation and maintenance

18 Benefits

19 Benefit-cost ratio i

Paragraph l

TABLE OF corrrEwe~- ( Cont 'd)

Subject

APPENDIX A - FOUNDATION AND MATERT~LS

General

Soils investigation

Laboratory testing

Existing conditions

Design criteria and recommended treatment

6 Detailed conditions and proposed l l improvements

APPENDIX B - HYDROLOGY

Climate

Stream flow characteristics

Flood stages

Flood frequencies

Water surface profiles

Upstream flood control storage

Interior drainage

APPENDIX C - ECONOMIC DATA

Introduction

Flood damage surveys

Computation of annual damages

A-1

A-1

A-1

A-2

A-3

A-3

B-1

B-2

B-3

B-4

B-5

B-6

B-6

C-1

C-1

C-2

4 Computation of flood-control benefits C-4

5 Potential development C-5 ii

TABLE OF CONTENTS (Cont'd)

TABLES

1 Cost estimate, main levee

2 Cost estimate, 142nd Avenue cross-levee

3 Cost estimate, pumping plant

4 Cost estimate, bank protection

5 Determination of average annual damages

6 Soil classification summary

CHARTS

1 Precipitation frequencies, Portland International Airport

2 1938 stage hydrograph, Vancouver

3 Frequency curves, maximum annual water surface river mile 114, summer flood

4 Frequency curves, maximum annual water

· surface river mile 114, winter flood

PLATES

1 Index plan

2 Plan, Sandy cross-levee and main levee, Station MD 0 to MD 32

3 Plan, Station MD 32 to ~ID 102

4 Plan, Station MD 102 to MD 179

5 Plan, Station MD 179 to ~ID 261

6 Plan, Station MD 261 to MD 343

7 Plan, Station :MD 343 to MD 424

8 Plan, Station MD 424 to MD 505

9 Plan, Station MD 505 to MD 604 iii

PLA'JlES (Cont'd)

10 Plan, Station MD 6014- to MD 690

11 Deleted 16 cr, CLw C*J.J ~-Ct ,. B -~k-~

12 Plan and profile, ll!-2nd Avenue cross-levee

13 Profiles Sandy cross-levee and main levee, Station MD 0 to MD 9J+

14 Profiles, Station MD 94 to MD 298

15 Profiles, Station MD to MD 298+494

16 Profiles, Station MD to ~ill 494+690+30

17 Pumping plant

18 r:coe drain and drainage structure details

19 Deleted

20 Maximum annual stages, Columbia River at Vancouver

21 Water surface profiles, Columbia River floods

22 Typical soil test results iv

MUII.PNOM/\H COUNTY DRAINJ\.GI~ Dlf31CHIC'I' NO. 1

DESIGN MEMORANDUM

1. Pertinent data. - Data relevant to the proposed improve-ment for Multnomah County Drainace District No. 1 in Multnomah

County, north of the City of Portland, Oregon, are itemized below:

Improvement of existing levee.

Reinforcement

Description: 1 on 5 fill on landward side from elevation +30 m.s.l.

Material: Dredged sand fill.

Quantity of sand required: 108,000 cubic yards.

Tot·al length of reinforcement: 14,600 feet.

Toe drains

Total length: 19,600 feet.

Estimated cost: $710,860

Cross Levee: 142nd Avenue

Top elevation: +41.2 feet m.s.l.

Top width: 12 feet

Side slopes: 1 on !.1-

Material: Dredged sand

Quantity of Hydraulic Fill: 327,090 C.Y.

Cross Levees: (Continued)

Drainage Structures:

Estimated cost:

1 !4-?.nd A venue

1-2 bbl. 66-inch

$392,570

Improvement of major interior draina.ee:

Channels to be improved: 2,000 feet.

Additional pumping capacity: 100,000 g.p.m.

Estimated cost: $614,310

Bank protection:

Linear feet: 14,6oo.

Estimated cost: $491,270

Total estimated project costs:

Federal:

Non-Federal:

Total:

Annual benefits:

Benefit-Cost Ratio:

$2,042,500

166,500

$2,209,000

$ 395,300

4.60 to 1

2. Project authorization. - This project for improvement of the Multnomah County Drainage District No. 1 was authorized by the Flood Control Act of May 17, 1950 (Public Law 516, 8lst

Congress, 2nd Session.) The project as proposed in House Docu ment 531, 8lst Congre~s, the project document, consists of works intended to protect the di.strict agatnst Columbia. River floods equivalent to the 1894 flood ( 1, 240,000 c. f. s. at rrhe Dalles) with freeboard. The project includes constructing toe drairw throughout the entire length of the riverfront levee, constructing four cross levees, installing additional pumpinG capacity, and im proving the major interior drainage system. The project document also authorizes 123,800 linear feet of bank protection works along the lower Columbia River at an estimated total cost of $4,900,000.

Some 9,900 linear feet of this bank protection are located in

Multnom~h County Drainage District No. 1, at an authorized cost of

$392,000. No Federal funds have been expended on improvements authorized by the ;Flood Control Act of 1950. Requirements for local cooperation are as specified in the authorizing legislation; and formal assurances of local cooperation have been recejved.

Between November 1939 and September 1941, the Corps of Engineers under authority of the 1936 Flood Control Act, reconstructed 53,000 feet of levee, using the 1894 flood level as a design criterion;

revetted 4,000 feet of levee; and reconstructed tl1e outlet struc ture at the pumping plant, all at a cost of $508,517 from Federal funds and $25,000 from contributed funds.

During the Columbia River flood of 1948,·the failure of a section of levee immediately south of the pumping plant resulted in the loss of the tide boxes and pumping plant, and the inundation of practically the entire district with losses estimated at nearly $8,ooo,ooo. Following the flood, the Corps of Engineers, under emergency repair authorizations, restored the damaged pro tective works, including the construction of a new pumping plant with increased capacity and the installation of a new tide box, at a cost of $8~~~7, lf{l.

In 1949, the Corps of Engineers completed work authorized under the 1936 Flood Control Act by increasing the height of the levee one foot above the confined 189l~ flood level for a distance of approximately 6,850 feet and revetting 1,500 feet of riverbank at a cost of $77,135·

In May 1956, in preparation for the anticipated major freshet, the Corps of Engineers revetted about 200 linear feet of actively eroding riverbank and flattened the landward slope of the existing levee with pervious embankment in a number of areas at a cost of

$81,032 Federal funds, plus a contribution of $30,000 by local interests. The 1956 work was completed under authority of Public

Law 99, 84th Congress.

The total Federal expenditure to date for work in Multnomah

County Drainage District No. 1 is $1,494,155·

Funds in the amount of $43,000 have been allotted for planning purposes, development of cost estimates, preparation of this design memorandum, and preparation of plans and specifications in Fiscc~l

Y1)ar lq)'{. I•'undc in the~ amount (>J' :1>)00,000 havf-~ t>c:cn Jnc1udccl i.n Lr1\ ~ l' L'cr-;idcnt 's Budc;ct for ird tJ.a tlon of eunr:l LrueL:lcJn .in

:3. !nvesti.{):i.tions. li'ield invc:.rU.{';:J .. tionD whlr~h have bcec carried out periodically r.rom 1939 to 19)'( :include! topcJgraphic

1;urveys of the main riverfront levee and of proposed .locatlorw

.for cross levees, hydroc;raphic surveys of portions of the inter ior drainage system, aerial reconnaissance of areas requirinc;

bank protection work, and foundation explorations consi~::ting of hand auger and churn drill borings at selected locations along riverfront and cross levee . Field investigations data include those in the studies leading to the improvements recommended in the authorizing document, House Document 5 31, Blst Ccm~:;rcu:>, 2nd

Session. Additional investigations since 19)0 inc1ude J.Ci( hand auger borinGS, 6 churn drill holeD, rtnd Jl. 7 mi1.es of survey.

Appendix A of this memorandum contains dttta on foundation mater ials. Recent borrow area explorn.tionc rtave not been made br~eause data. avalla.ble from the Sandy eross l.cvee construction is con sidered to be applicable to this project.

h. Local cooperation and views. - Public L1w 516, 8lst

Congress, requires that local interests (a) provide without cost to the United States all lands, easements, and ric~to-of-way;

(b) make all necessary highway, highway bridge, and utility alterations; (c) hold and save the United States free from all damages due to the construction works; and (d) maintain and operate the works after completion in accordance with regulations prescribed by the Secretary of the Ar.my. Multnomah County Drain-age District No. 1 is organized and operates under state of Oregon law. It has the authority and the ability to carry out the re quirements of local cooperation and has so demonstrated in the past by satisfactorily operating and maintaining flood control works constructed by the Corps of Engineers. No public hearings have been held, but in conferences and by letter dated 17 December 1957 the Drain age District has indicated its support of the project. In these in formal assurances the Drainage District has indicated its ability to furnish all required items. The estimated cost of local cooperation is $166,500, of Which $80,420 is for rights-of-way. The cost of rights of-way breaks down to $25,510 for main riverfront levee improvement.

$48,080 for the 11+2nd Avenue cror:HJ levee, and ~!t),8"jO for the new pumping plant. Formal nssurancPrJ of local cooperation wc~rc received by the District Enc;ineer on 3 Apr:t.l 1957.

In 1954, the Drainage District, in cooperation with th(:

Sandy Drainage District, constructed to pro,ject standards onC' of the cross levees authorized by the project document. rrhin levee is located along Campbell Road at the east end of Multnomu.h

County Drainage District No. 1, and separates it from Sandy Drain-age District. Completion of the cross levee has reduced the estimated cost of improvements for Multnomah County Drainage

District No. 1 by $368,900.

The Drainage District has an active maintenance and operation program, requiring the annual expenditure of about $20,600 for operation and maintenance of Federally constructed workt>. rrhc annual cost of operating and maintaining flood control workG in the district after construction of the project outlined herein is estimated to be about $28,700. Principal officers responsible for fulfillment of local cooperation are:

s. B. Hall, President

Lew Russell, Supervisor

Geo. W. Clarke, Supervisor

A. N. Scritsmier, Manager and Secretary-Treasurer

'I'he add resn of the above officials is Mul tnomah County Drainar,e

District No. 1, 10319 N. E. Marx Street, Portland 20, Oregon.

5· Location of project and tributary area. - Multnomah

County Drainage District No. 1 is located in Multnomn.h County, Oregon, and adjoins the northeast limits of the city of Portland.

The district occupies an area approximately one mile wide along the left bank of Columbia River between river miles 108.2 and

119.0. The Union Pacific Railroad and U. s. Highway No. 30

parallel the south boundary. The diBtrict is separated from

Peninsula Drainage District No. 2 on the west by levees along the

Peninsula drainage canal, and is separated from Sandy Drainage

District on the east by a cross levee. The district contains a total of 8,417 acres, 465 of which are occupied by Blue Lalce, Fairview lake, Columbia Slough, and a few small ponds and f:lloughs.

Approximately 3,910 acres are highly developed farm land while

2,500 acres near the west end are occupied by the Portland Inter national Airport. Blue UU{e Park, three well-developed golf courses, and several small but active industrial enterprises, and suburban developments occupy the remainder of the area. Land elevations within the district range from 12 to 25 feet, mean sea level.

':Plw dJ.crLr:Lct wao or[r,anized in 1917. DurJ ' 1 r~: t~hc~ p(;rJod. frnrn

1919 to 19~~1, loeal i.ntercsts prov1c1cd, n.t o. rcportc(i cont of

$)96, ~~92, primary J:>rotection consi crt :inc; oi': (a) (jc;, 'T)O fr :r~ t of levee alon8 Columbi.a River d.owrwtrc~mn from the Sandy Dra:irw.r_~e

District .levee and along Peninsula draina[r,c canal, dcs.i r_-:necl to protect the area against a flood equal to that whic:h occu.rrr~d. in

1876; (b) a main pumping plant on Columbia S1oue;h; (c) five tide boxes; and (d) five auxiliary pumpinc; plants in the inter ior of the district. Between 1921 and 1939, local interr2sts raised and strengthened a portion of the levee and rcvetted critical areas but the cost of this work is unknown.

In addition to the 8,417 acres in the District prnpc;· there are approximately 11,600 acres of higher r;round tc1 thr~~ sou.th · .... ttJ.d-;

contribute to the rtm-off and which m1wt be hctnd.1ecl ~)Y dn:dnncc and pumping facilities in the district. B:i. nee 191+(), expa.nsion of the northeast part of Portland has moved. the liwi ts of the built-up suburban resi.dential area eastward nearly four miles.

Pavement and roof areas have replaced and r1re continuing to replace a large amount of farm and forest acreage, there1Jy increasing the peak and total run-off which must be handled by the District's drainage system.

6. Projec~la~. - The baoic approved dcsisn criteria adopted for all flood protection projects on the lower Columbia

Ri vcr provides protection against an 189J+ flood as controlled by upstream storage now ex:lstinr;, under construction, or reason-ably certain of being constructed. The flows so modified within the , project area would be confined by existing levees and the re-sulting stage would determine the levee design and top eleva-tion. The existing levee fronting Columbia River in Multnomah

County Drainage District No. 1 has ample elevation to prevent overflow during the design flood, but requires improvements as described herein to control seepage and increase slope stability.

The cross levee between the Sandy and Multnomah Districts, which is a part of the authorized improvements to Multnomah District, was built by local interests to the elevation of the riverfront levee to protect either district in case of failure of the main levee in the other district.

The existing levee is constructed of sand, silt, sandy silt, and clay. The top grade is generally at, or above the confined

1894 flood level. Top widths vary between 12 and 56 feet. How ever, approximately 14,600 linear feet of levee are considered inadequate in section, and approximately 19,600 linear feet of levee are considered inadequately drained, to withstand a stage produced by a flow of 940,000 c.f.s. at The Dalles.

The existing Multnomah levee, totaling about 13.1 miles in length, protects over 8,400 acres with no effective cross levees or other physical separation. Thus, during a major flood the entire district would be inundated should the main levee fail, as it did in 1948.

During the 1948 flood and subsequent smaller floods, a number of areas behind the existing levee in Multnomah District were observed to seep excessively. Several of those locations required constant attention to prevent or contain boils and pre vent disastrous sloughing of the levee slope. Determination of the limits and treatment of those areas of excessive seepage was th~ principal problem in connection with improvement of the river front levee. Logs of auger borings and churndrill holes, as well as data obtained during the flood fight, revealed the areas .re quiring added protection. Areas requiring improvement are shown on attached plates.

Toe drains with laterals will be installed in the sections where serious stratification exists in the levee or foundation, or in both. Graded filters will be required for the pipe drains.

Construction of one cross levee at 11+2nd Avenue, as indicated on Plates 1 and 12, is planned. Material dredged from the Columbia River will be used for the major portion of the cross levee. A drainage st~1cture equipped with automatic and manual gates will be installed where the cross -levee intersects the e~~sting ma,jor drainage channel.

A storm of three year frequency in December 1955 severely taxed the existing pumping plant with its 135,000 g.p.m. capacity.

Existing pump capacity is considered to be inadequate considering the present development of the Drainage District and tributary area. Construction of 100,000 g.p.m. additional pumping capacity can be expected to handle run-off due to a 10-year storm under foreseeable development conditions. Because hydrology studies indicate that 44% of the run-off which enters or is generated within the district does so east of 142nd Avenue, it is felt that more efficient pumping can be effected by placing the addi tional pumping ,facilities east of the 11+2nd Avenue cross levee rather than by enlarging the existing pumping plant. Such loca tion of the additional pumping facilities vrould also permit ci th:.~r pumping plant to operate in case of a break in the levee protcctinc; the other plant.

Bank erosion is active in 12 areas, for a total of

J)l ,600 linear feet along the existins levee. Bank pro-tection of dwnped stone revetment is considered neces-sary to protect the ex:isting and :proposed flood control works.

7. Departures from project document plal_!· Pro-tectlon authorized by the 1950 Flood Control Act r,ras ar;a.inst a flood of i89l1. magnitude uneontrolled, a 135-year flood. With proposed flood routings, and an 18')!t· flood controlled by upstream storage now exist.lng, under constru~tion, or reasonably certain of being constru~ted as tabulated in appendix B, a reduction of f1o'\v can be effected from 1,2 1-~0,000 c.f.s. to

91.~0,000 c.f.s. at The Dalles. This is the criterion covering the proposed work. in Mu1tnomah County Drainage

District No. 1. r.rhis reduction 1n design flood height at the mid-point ot the District from 41.5 feet to 35.0 feet, has eliminated the need for work in some areas and reduced the magnitude of the work in areas still requiring improvement.

The construction by local interests of the cross levee between Sandy and Multnomah County

Drainage Districts eliminates this structure from the plan of improvement.

At the time the project document was prepared, local interests could not guarantee right-of-way for reinforcing the front levee along Columbia

Slough between the existing pump house and Union

Avenue. A short cross levee isolating the small area between Union Avenue and the pump house and between the slough and Columbia Boulevard was con sidered necessary to protect adequately the re mainder of the Drainage District. Right-of-way difficulties haYe since been resolved, and it will be more economical to reinforce the front levee than to construct the short cross levee.

Recent investigations reveal that bank erosion en dangers the existing levee along the Columbia River for a total of 11~,600 linear feet. This is an increase of

4,500 linear feet from the 9,900 authorized by the project document.

8. Hydrology. - Multnomah County Drainage District

No. 1 is located in an area subject to about 40 inches of rain per year, but rainfall in the vicinity of the district has little effect upon the floods to which the district is subjected. The Columbia River drains a large mountainous area from which snow melt run-off produces heavy flows in the late spring. Winter floods caused by local rainfall are of secondary importance.

Floods of record on the lower Columbia River have pro duced stages at the mid-point of the district of approxi mately 39.2 feet in 1894, 36.0 feet in 1948, and 33·7 feet in 1876. Flood stage at this same point is approximately

20.6 feet. In the last 81 years, a stage of 30.1 feet has been exceeded twelve times. Plates 20 and 21 show maximum annual stages for the Columbia River at Vancouver and water surface profiles for selected floods, and plate 21 shows the regulated stage of the 1894 flood, which has been adopted as the levee design flood. As shown in Ap-pendix B, upstream storage would reduce the flow of the

1894 flood from 1,240,000 c.f'.H. to 940,000 c.f.s. at

The Dalles.

An area of appro xi rna tely 20, o.oo acres contributes run-off which must be handled by the district, although only about 8,400 acres are in the district and therefore taxable for upkeep and operation of the pumping and drain age facilities. Because of changed land usage, pumping capacity is rapidly becoming inadequate and additional capacity is necessary. See Appendix B, Hydrology, for a detailed discussion of run-off conditions affecting

Multnomah County Drainage District No. 1.

9. Geology. - Multnomah County Drainage District No. 1 is a diked-off portion of the Columbia River flood plain.

The materials undf~rlying the flood plain to approximate elevation -80 l~et are stratified sediments consisting of silts, clays, sands, and blends of these materials.

In the western part of the district water wells penetrate gravel at approximately elevation -80 feet. In the eastern part of the district, knolls of Troutdale formation sand stone and conglomerate extend out from the valley side and are exposed in the riverbank just west of Blue Lake.

These sills formed protective bulwarks against scouring of the older coarse materials which underlie the fine sediments, so that north and west of the hills loose peM'ious gravel rises to within a few feet of the surface.

The contact between the gravel and the fine sediments slopes of:f' sharply to the north and west. Just west of 138th

Avenue a shelf of Troutdale formation sandstone lying slightly below zero elevation extends out beneath the flood plain to a point just north of Columbia Slough.

From there it apparently slopes off rapidly to the north.

This shelf undoubtedly also rises gently to the east to join the knolls near Blue Lake. A narrow channelled continuation of this shelf also was picked up in the vicinity of 96th

Avenue. In both cases no gravel was present and tl:E fine sediments rest directly upon the rock. Leakage from the

Columbia River into the proposed diked area appears to be probable near·Blue Lake, where coarse pervious gravel rises almost to the surface. Leakage via the coarser sand beds is also possible, as is some dike settlement across areas of clayey silty sediments.

10. Other plans investigated. - Serious consideration was given to expansion of the existing pumping plant by

100,000 g.p.m. and enlargement of major interior drainage canals to drain the district as efficiently as the pro posed pumping plant at the east end of the district. This plan was abandoned when the estimated cost of improving the canals was found to be in excess of $800,000, while the only gain which might be realized would be the cost of a common wall between pump houses. This plan would also lack the flexibility in pump operation offered by the proposed plan.

The construction of a cross levee in the vicinity of

122nd Avenue was investigated. This plan was abandoned due to right-of-way problems. Construction of a second levee at 96th Avenue was also investigated. However, because of lack of local interest this plan was abandoned.

Excavation of a trench along the riverside slope of the front levee and backfilling with impervious material was considered, but this plan was abandoned when its cost was compared with the proposed installation of toe drains and blanketing the landward slope.

11. Description of proposed structures and improvements. -

The existing works are described in general in paragraphs 2 n.ud ) nl)()Ve. rrhe ex.Lr;l. LH{j lcvc~e ha~~ cur t'.lc:l cnt height to protect against a flood equivalent to that of 1894, but stratification of embankment and foundation materials permits excessi V(~ seepage during extended high river stages. Conse quently, after saturation of the levee, sJoughi.ng and sliding of the landward slope can take place, and. boils occur in scattered locations. The existing levee is considered adequate for a discharge of not more than 850,000 c.f.s.

at The Dalles. It is proposed to blanket the landward slope of the levee with pervious material, and install pipe drains surrounded with graded material at all locatJons where heavy seepage has been observed or where soils exploration~ indicate that such work is essential. The pervious blanket material will be placed on 1 on 5 slopes. Attached Plate 18 shows toe drain details. Pervious blankets will be covered with

4-inches of top soil and seeded to prevent wind and rain erosion. Sluice gates will be added to the ti.de box adjacent to the existing pumping plant. The pervious cross-levee con structed of dredged sand will have a 12-foot top width and

1 on 4 side slopes. A four inch blanket of top soil will be placed on the sand and sown with hardy grasses to prevent wind and rain erosion. Levee top will be surfaced with 6 inches of crushed stone to permit emergency access for flood fight equipment and to allow maintenance and inspection vehicles to traverse the levee. Turnouts will be provided every 1,000 feet. The 142nd Avenue levee will have a top elevation of +41.2 feet m.s.l. This top elevation is based on the design river profile, plus a 3-foot freeboard, plus a 1-foot safety factor to allow for surges and wave action. Cross-levee design grade was selected to protect against the design river stage in case of riverfront levee failure at the upstream end of the compartmented area. Protection by cross-levee is to same criterion as front levee, but raised 1 foot above design grad~of front levee to prevent downstream damage from an upstream break. A drainage structure consisting of two 66-inch diameter corrugated metal pipe culverts with automatic gates on the west end and manual slide gates on the east end will be installed in the major drainage canal as indicated on plates 1, 12, and 18.

Criteria for design of the drainage structure in the cross levee contemplate inflow from a 25-year storm with no pumping plant operating in the east end of the district. An additional 10 percent safety factor was allowed for the drain age structure in the 142nd Avenue levee because of the pre dom~nantly agricultural nature of the land east of this levee.

The automatic gates are provided on the west end to permit gravity drainage of the District during low river stages, and will protect in case of a break downstream from the cross levee. Manual gates will be closed only in case of a break in the levee upstream from the cross-levee. This drainage structure will be equipped with seep rings to prevent water from Channeling directly along the outside of the pipes. Where roads cross the levee they will be relocated by ramping over the top rather than through openings with stop logs. Para graph !~208.25,n, Orders and Regulations, prescribes that ramp construction be done at Federal expense.

Hydrologic data indicate that the existing pumping plant with its capacity of 135,000 g.p.m. can handle expected run-off and seepage for the district west of the 142nd Avenue cross levee with little difficulty. Except for periods of heavy rain fall, when flooding of the district occurs, the existing pumping plant can handle interior drainage for the entire district. It is to prevent flooding during 24-hour storms of 3-year frequency and to remove seepage water from the east end of the district in case of levee failure to the west that the additional pumping plant with a capacity of 100,000 g.p.m. is required. The pro posed location of the new pumping plant permits use of a portion of old Columbia Slough for the major part of the channel leading to the forebay. It will be necessary to excavate about 600 feet of new channel and clean and grade about 1,400 feet of existing slough channel. Alignment and cross-sections of the proposed new and improved channels are shown on plate 4.

An indoor type pumping plant has been selected for study for this memorandum. Although an indoor type plant is some what more expensive, the vulnerability of the outdoor plant to vandalism, the inconvenience and discomfort of operating the outdoor plant in bad weather, the added cost of weather proofing switch gear, and the fact that local interests desire an indoor plant favored the ultimate selection of the indoor type.

The indoor type pumping plant, shown on plate 17 is of reinforced concrete supported on timber piling. Piling with cut-off below ground water will be untreated and piling extend ing above ground water will be treated. The natural topography of the site, the water surface elevation in the forebay of +6 m.s.l., and the characteristics of the pumps were used to determine the elevation of the pump deck and the dimensions and bottom elevation of the sump. The site will be graded to provide drainage away from the structure. Security for the pumping plant will be provided by fencing. Protection from floating debris will be provided by a floating trash rack in the forebay approach channel and trash racks at the sump intake. Stoplog slots are provid.ed for unwatering the sumps for maintenance or repair. Transformers will be located on a concrete slab adjoining the pump deck, and switch gear will be installed in the pump house. The transformer slab will be fenced for security and safety. Electricity is available at the site.

The pumping plant will consist of four vertical propeller or mixed flow pumps driven by induction motors. Static heads will vary between a minimum of 2.5 feet at low river level to

30. ;, feet with river level equal to 1948 flood. The invert elevation of the discharge pipes will be 30 feet m.s.l. and siphon effect will be utilized at intermediate and low heads to reduce horsepower and increase pumping capacity. Design criteria calls for a pumping capacity of 100,000 g.p.m. under relatively low static head conditions of 8 to 15 feet, and 40,000 g.p.m. under high static head conditions of 31.5 feet. Pro vision has been made for two pumps which will operate efficiently at the lower heads with a combined discharge of 60,000 g.p.m.

The other two pumps will operate efficiently at maximum head and no siphon effect with a combined discharge of 40,000 g.p.m.

and under low head conditions will discharge slightly more than

60,000 g.p.m.

Each pump will discharge through a separate pipe, 420 feet long, with a minimum velocity of 5 feet per second to insure good siphon effect. Three expansion couplings and two valves will be provided in each pipe, one gate valve on the riverside of the dike and an hydraulically operated butterfly valve in the pump house. The belled discharge ends of the pipes will be submerged at low river stages.

A low capacity higb head service pump will be provided to furnish water for operating hydraulic cylinders and for vacuum pump seal water. A vacuum pump to prime the discharge pipes will be installed. A low capacity low head pump will be provided to unwater the sumps. All auxiliary equipment and piping including the butterfly valves will be installed below the main floor in a heated inclosure for protection against freezing.

A separate design memorandum is being prepared for the pro posed pumping plant.

Bank protection consisting of 18 inches of dumped stone revetment over 12 inches of filter material is to be placed in

12 locations. The total length of the proposed bank protection is 14,600 linear feet. Bank protection work is shown on Plate 1.

High river stages have caused trouble at two places along the Peninsula Drainage Canal where pipes pass through the levee.

These pipes are no longer in use so the situation will be corrected by excavating the levee, removing the pipes, and backfilling.

12. Sources of construction materials. - Coarse to fine sands and fine gravels are available in the bed of the

Columbia River and from previous experience have proven to be suitable for pervious levee and blanket construction.

This material can be placed quickly and economically by hydraulic methods. The existing pwnping and drainage works supplemented if necessary by emergency pumps will remove water required for dredge operation from the District.

Top soil to blanket the pervious material and support the desired grass cover may be obtained while improving interior drainage channels or from borrow areas within the

Drainage District.

Graded sand and gravel, concrete aggregates, revetment stone, and ready-mixed concrete are available from several commercial sources in the Portland area.

Corrugated metal and concrete pipe for toe drains and drainage structures, gates, valves, pumps, trash racks, electrical equipment, reinforcing steel, and auxiliary control equipment are all available, or can be ordered through suppliers in the Portland area.

13. Real estate requirements. - Local interests are re quired to furnish all rights-of-way for the project. Where additional lands are required for performance of the proposed work, right-of-way lines are shown on plates 2 through 12.

14. Relocations. - A high voltage electrical transmis-sion line on the landward toe of the riverfront levee must be relocated between Stations 36 and 65. Local roads, streets, and bridges must be moved where they are on land to be occupied by the cross-levees. Some houses, farm buildings, fences, and utilities must be moved or removed. Minor interior drainage must be relocated where cross-levee blocks existing channel.

Minor interior drains carrying run-off from the proposed toe drains must be improved or relocated. Local interests are required to accomplish all relocations except road ramps.

15. Cost estimates. - Total project costs are shown sum-marized as follows:

Amount Feature Federal Non-Federal Total

Permanent Features:

Lands and damages $ 550 $ 80,420 $ 80,970 Relocations ~6.220 :16,220 Levees

381,610 Embankment 381~610 Seepage control measures 333,840 333,840 Drainage facilities 116,990 29,140 146,130

Major interior drainage Pumping plant 430,340 1,550 431,890 Channel improvement 95,350 95' 350

Bank protection 417' 350 417' 350 Subtotal $1,776,030 $147,330 $1,923,360

15. Cost estimates. - (Continued)

Feature Federal Non-Federal Total

Distributive costs:

Ensineering and design $ 106,530 $ 8,840 $ 115' 370 Inspection 124,440 124' 41~0 Other distributive costs 35,520 10' 320 45,840

Subtotal $ 226,490 $ 19,160 $ 285,650

TOTAL PROJECT COST $ 2,042,520 $ 166,490 $ 2,209,010

Say ($ 2,042,500 $ 166,500 $ 2,209,000)

These figures agree with the PB-3 estimate as revised by addition of superstructure to pumping plant, sluice gates on existing tide box, and construction of one cross-levee at 142nd

Avenue.

The foregoing estimate, which includes contingencies, engineer-ing, inspection, and overhead costs, amounts to approximately

$243 per acre in Federal costs for 8,417 acres to be protected.

The Flood Control Act of 1950 authorized improvements to exist-ing works in Multnomah County Drainage District No. 1 at a Federal cost of $1,365,000, and bank protection work at a Federal cost of $392,000. Changed conditions described above which resulted in design changes and a 36% increase in the cost of construction have raised the estimated cost to $2,042,500 in spite of the elimination of Sandy cross-levee. Increases in the price of real estate account for a large part of the increase in non-

Federal costs from $52,000 to $166,500.

With interest at 2-l/2/o and amortization in 50 years, annual charges would be as follows:

Item

Interest and runortization Operation and maintenance

Total

Federal

$72,020

$72,020

Non-Federal

$5,870 8,100~-

$13,970

Total

$77,890 8,100

$85,990

-*· Inc::r.·emental operation and maintenance cost due to construction of this project. Not total operation and maintenance cost.

16. Schedules for design and construction. - Plans and specifications for reinforcement of the main levee are expected to be completed and submitted to higher authority for approval prior to 1 June 1957· It is expected that construction will be initiated when Fiscal Year 1958 funds become available. Installa-tion of toe drains and blanketing the landward slope where required on the main riverfront levee would be initiated during the second half of Fiscal Year 1958 and would be completed insofar as possible with available funds. Plans and specifications for the 142nd Avenue cross-levee with appurtenant drainage structures are expected to ?e completed and forwarded to higher authority for approval in the near future. Contingent upon appropriations, the 142nd Avenue cross-levee and appurtenant drainage structures and bank protection work in critical areas would be completed in Fiscal Year 1959· The pumping plant, improvement of interior drainage, and remaining bank protection, would be constructed in Fiscal Year 1960, con-tingent upon appropriations. All construction work would be performed by contract and each r>e[911cmt of' couutruction vTOrk would be completed within one fiscal year.

17. Operation and maintenance. -Improvements proposed for the second half of Fiscal Year 1958 should not increase the drainuge district's maintenance costs in any way and in the event of a flood fight, can be expected to reduce their operating costs by better controlling seepage through the levee.

Construction of the cross levee and bank protection can be expected to increase the drainage district's maintenance costs slightly because of the additional area that will require care. Maintenance of the new pumping plant will require addi tional expenditures, but unless water levels in the district are pumped down lower than at present, pumping power costs should not increase and may in fact decrease. Except during periods of heavy run-off, the additional pumping capacity will permit operation to be restricted to off-peak power hours, ef fecting a considerable saving. Improving the hydraulic characteristics of channels leading to the new pumping plant can be expected to improve over-all pumping efficiency, further decreasing costs. The principal increase in District's costs for this additional pumping capacity would be incurred by the addition of a pump operator. Non-Federal annual maintenance and operation costs after eomplction of the final phase of the work are cstima.ted to be about $28,700.

18. Bencfi ts. - fJ.'he district devclopmcntf-3 comprise 715 homes with a population of about 3,000, a higbly productive suburban agricultural area, industrial and commercial establish ments, International Airport and U. S. Air Base. Land values range from $750 to $1,500 per acre, the more valuable land being adjacent to the airport and industrial sites. The acreage is divided into the following categories: Agri cultural, 3,910; industrial and commercial, 300; resi-dential tracts, 1,070; recreational areas, 500; airport and U. S. Air Base, 2,500; and nonassessaale, 150. Agri cultural income is estimated at $1,500,000 or about $400 per acre.

The Portland International Airport, owned and operated by the Port of Portland, occupies about 2,000 acres. New construction started in 1956 to be completed in 1960 will bring the Port of Portland's holdings to a total of about

$22,000,000 with the possibility of further runway extensions and improvements to cost an estimated additional $5,000,000.

Nine airlines operating at the field have a combined assessed valuation of $1,302,000. The Portland Air Base and National

Guard area is about 450 acres. Outside the Port property, commercial and industrial enterpriuos occupy lawl valued at over $2,000,000. Recreational facilitieD include three golf courses and a conunercial park.

'I'he existing levee is considered adequate to protect the district against flows up to 850,000 c.f.s. at The Dallen.

rrhe present annual damages, with existing storage, amount to

$491,800, and at the expected rate of development will in crease to $708,200 annually by 1980 at 1956 price levels.

These damage estimates are based on flood frequencies and stages as discussed in Appendix B, and on the surveys and evaluations of damages discussed in Appendix c. The derivation of annual damages and benefits from reduction of damages with the existing degree of protection and economic developments are shown in Table 5.

With levee improvements to provide protection against

940,000 c.f.s., the present annual damage would be reduced by $274,500. Future storage may be expected to further reduce the remaining damages. The additional protection from proposed improvements would encourage industrial and other developments which have not been evaluated.

Mul tnomab. Drainage District covers 8, l~OO acres and about

5o% of the district is still used for agricultural purposes, but this area is steadily declining as more intensive uses of the land are developed. The location of the district with good transportation facilities, adjacent population centers, and the presence of several successful enterprises all indicate the probability of continued economic growth. It is believed that the increase of 2% per annum forecast for the surrounding area as shown in Appendix C is a conservative estimate of the probable growth of this district. On this basis the total evaluated annual benefit with 1980 development for the levee and bank protection improvements is estimated at $395,300.

19. Benefit-cost ratio. - With average annual costs of

$85,990 and average annual benefits of $395,300, the benefit cost ratio is 4.60 to 1.

APPENDIX A

FOUNDATION AND MATERIALS INVESTIGNTIONS

1. General. - The deslgn as presented in this report covers the Jmprovements to the Multnomah County Drainage

District No. 1 levee system and construction of one cross levee within the Multnomah Drainage District.

2. Soils investigations. - Prior to the levee improve ment in l9lt-0-41 there were 247 exploration holes made along the main levee. After the 1948 flood 131 hand auger holes were bored in troublesome areas. In 1956 the Port of

Portland drilled 4 churn drill borings and 19 hn,nd. auger holes at the upstream end of the main levee. Hecent explorations consisted of 28 hand auger holes along the main levee in areas of seepage during the 1956 flood;

18 hand auger holes and one churn clrj, 11 hole on the 142nd

Avenue cross levee; 9.nd one hand auger and one churn drill hole at the proposed pump house location. Logs of the exploration holes are ihown on the profiles on plates 13, 14, 15, and 16.

3· Laboratory testing. - Mechanical analysis and

Atterberg limits tests \..rere perfonned on representative

A-1 samples for the 1939, 1948, 1952, and 1956 explorations.

Classification of materials from the 1939 exploration was changed, by use of field logs and laboratory test results, to conform with the Corps of Engineers standard classifica tion. Table 6 contains a summary of the classification data.

4. Existing conditions. - a. Main levee. - Prior to 1939 the levee was built to elevations varying from 34 to 37 feet m.s.l. from Station 0+00 to about Station 500+00, and to approximately 40 feet m.s.l. from Station 500+00 to the intersection of the levee with high ground near Union

Avenue. The levee was constructed in general of impervious material on a foundation that consisted of semi-pervious to impervious materials. Improvements in 1940-41 consisted of raising the levee along the Columbia River to elevation 44.

The material consisted mainly of dredged sand. The levee along the Portland International Airport was raised with compacted impervious materials over the original levee and dredged sand fill placed on the landward side. The levee along the Columbia Slough was raised slightly and the water side slopes flattened by cutting. The excavated material was placed on the landside slopes.

'b. Cross levee. - At line "D" (142nd Avenue cross levee) the foundation consists generally of silts, with bedrock at shallow depths at the south end of the levee.

A-2

t. ion c ,:1111:1 irlorod i.n the do:Ji en or the improvcrnentn 0 f t hr.; levr;::l) consl:~toc1 of e:xplorntion lor:s ·with laboratory tent rocults e .. nrl nv0.iLJblo rocordu i'row tho 194:0 and 195G flood[~~. Soop:Jc;c study for ero ss levee location is shown on plate 22.

a. !~,Lin lev'.:30. - The lovee along th8 Columbia Ri.ver hnD an adocp.l:_1 to sect ion for sta bi li ty ae:ai nst E5lid inr:, under steady soepnc;e conditions. Improve~nont consists of tnstalling toe drains with cr3d.ed filtl;rs in arens of critical seepage. In

&reas where existins slopes are relatively ste0p additional per-vj_ous fill ·:Jill be placed on a 1 on 5 slope from elevation 30.

The Columbia Slou~h nrea cont.3incd the levae ;:>r::ction thnt failed in the 1948 flood.

b.. Cross le~. - .Seopsee st.udies made for the two ceneral founduti,)n cond:itions: Mod~rately impervious, :lnd shallow berlrock, "incU ca te th.'1 t a sr1nd fi.ll \'Ji th 1 on 4 nide slopes vJill be adequate.

l:n t n. Lev·2o __ . ._..,._,~"-- Q_rou~. (Station 36+00 to 65+00)

General conditions: Foundation and original levee moderately inpo:r.-viouB; orie;tnal iJ.~tpC.lrvlous levee section belm·J design flood;

r3 '~rious seopa{~e dnring 1948 and 1956 floods.

Improvem~mt: In:::;toll too drains.

A-3

GrounD. (Stations :315 to 356; 42S to 1;50; IJ17+50 to !50n+l0)

Gonornl conditions: l•'muvlntion and originel levoo semi-pervious nnd strntifieJ; serious seepa~o during 1948 and 1956 floods.

Improvement: Install toe drains. Dand fill stu 432-1 36.

Grot!2_.Q• ( Stn ti ons ;)08-t-lOt;o 535+00 and 524+~~0 to 600+00)

Genorul conclltions: Foundation oncl levee 0omi-pervious and stratified; lnndside slopes 1 on 1.8 to 1 on 3·

.heavy G(:Jepago durinG 1948 and 1956 floods.

Improvement: In stall toe drains ond le1ndside sartd fi 11 VJi th

1 on 5 slopes from elevation 30.

Groul?....12.• (Station 600+00 to 683+50}

G-eneral conditions: Foundation and lcvoe moderately im-pervious; 1Gndside n1opes 1 on 1.8 to 1 on 3. General ::>oep!33e durine; 1948 and 1956 floods.

Improvement: L'lndside sand fill with 1 on 5 slop3s from elevation 30.

~p E~ (Stations 0+00 to 36; 65 t,o 315; 356 to 425; 438 to

447+50; and 535 to 574+20)

General co:1.d:itions: Fonudation a.nd 1·:-Jvee moddrutely im-parvious; landside slopes 1 on 3e5 to 1 on 6; minor seepage observed durinc 1943 and 1956 floods.

Improvemont: lJono require(l.

A-4

Croos Levee

Group F.

General conditions. -

*Line D Stations 0+00 - 20+00

Line D Stations 20+00- 39+75

* Line D - l42nd Avenue cross levee.

Foundation moder ately impervious to a cnnsiderable depth.

Foundation moder ately impervious with sandstone bedrock at r:.hallow depths.

New work. - Construct sand levee with l on 4 side slopes.

A-5

General conditions.-

*Line B

Line B

*Line D

Line B

Line D

Stations 0+00 - 25+00

Stations 25+00 - 50+00)

Stations 0+00 - 20+00 )

Station 50+00 - 62+00 )

Stations 20+00 - 39+?5)

Foundation moderately pervious and strati fied.

Foundation moderately impervious to a con siderable depth.

Foundation moderately impervious with sand stone bedrock at shallow depths.

Ne\~ work.- Construct sand levee with 1 on 4 side slopes.

*Line B = 96th Avenue cross levee.

Line D a 142nd Avenue cross lave~.

.'\.J'J>:_•;.l':-!HX B -------

~.E t.l1 tho c.x\:.()ptiion of short fK!riodr.: or continnntul air ;oas[J eon-

·;··'rinci;)r.d. clinntic controls nre proximity to the j~'ucif:ic Occ:n1, 1nG loc~tion noar the conter of the oiddle-latitude halt of pro-vni.linr_;: VJG3torly wind~::,. Tl1o nroa iEJ subjoct to frequent storms of v:..1ried intennltiea. Chu.rt I for tbr~ I'o:t·t.Lnnd International d.irport. ::t!lOVJ:; precipitation frequencies for the rainy sea:·:on of t:1o yCL(.C, Uove:ilbor throuc~h ·i'liurch. TvJonty-four hour rainfall n.mountc of 2, 3, ::utcl 4 inches can be expected to re(;ur OV(:!r the L'.1ltnr');";~Jh

D1':J.i:nnr;e D.istrict on an nverseo of 1, 3 nnd ~35 years, rc:3poe·t.i.vo1y.

hvrr;1ul annual precipitatlon is nbout 40 incho:.J, of ·.Jhieh about

60 p1:n·,~cnt occurs durinG the period Novc:mbcr throush 7'::-:r·eh, ·v',:rd.lo less th:1n 4 perc on t, occurs during the J'uly-.l\u.r) l.:: t porioc1. On the ci.pitr1tion. Ar.munl totnls var.f fro;n about 2.5 to G5 inr~lF;s. .\ver-ac;e total onnuc1l Dnowfc,ll is about ono foot, n1oa~3urahlo amounts nccurr.·ing on an a.verrJ.t;O of 5 d:.ys por yo~nr. Duration of .snow on

~.7,round i r~ gm1crall~r 1 to 3 dr:1ys, d(3pths seldc11r1 exceed ine; 2 or ~?

tncho:3. A mux)..rnu,n depth of over 20 inches hos bf:·:;n rr:3corc1od in

1·.:1e cr,ono:c-:tl area of tho draina(~O dl[:;t.rlct, whoro~Js a depth of 6

D-1

Because of maritime influences. the annual ran.r!,e of tem peratures is comparatively narrow, mean monthly normals ranging from 37° F. in January to 67° in July and August. On the aver age, less than 30 days have temperatures below freezing and less than 10 days have temperatures above 90° F. each year; extremes above 100° F. and below 0° F. are rare. Except for heavy pre cipitation and occasional high winds or freezing rains, the area is relatively free of destructive climatic elements.

2. Stream flow characteristics. - The seasonal stream flow pattern for lower Columbia River is quite consistent in that low flows normally occur from September through March and hie.,b. sus tained flows prevail from mid-May to mid-July, with a gradual transition between the low and high flow periods. This pattern of run-off is almost the opposite of the annual precipitation pattern. A large percent of the annual precipitation which occurs during the winter months falls as snow and accumulates to great depths in the mountains. In the spring the snow melts, producing an extended high water period in the lower Col1.unbia River.

Occasionally during the winter, warm rains over the lower trib utaries produce moderately high water. stages of 3 days or less duration on the lower Columbia River opposite Multnomah Drainage

District. The flow regimen of the Colwnbia River in the vicinity of the Multnomah Drainage District is illustrated by the 1938 stage hydrograph at Vancouver, chart 2. Vancouver is on the oppo site side of the river and about 2 miles downstream from the lower

B-2 end of th·) district. rrhe stnr,e hydl.,Ofjraph i ln;:tr:tton all J':te~Jt:J of tho annual flo·.v pnttarn showinG tho orfuc:t::; of the ticlo during the year and both a winter freshot nnd a stunner fror:hct.