CEB523-T1-S1-2005

CEB523-T1-S1-2005 - GUT Student Number Surname Given Name/s...

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Unformatted text preview: GUT Student Number Surname Given Name/s Examination Paper SEMESTER: FIRST SEMESTER EXAMINATIONS 2005 UNIT: CEBS23 ENVIRONMENTAL GEOTECHNOLOGY - THEORY 1 DURATION OF EXAMINATION: PERUSAL: 10 MINUTES WORKING: 3 HOURS EXAMINATION MATERIAL SUPPLIED BY THE UNIVERSITY: EXAMINATION BOOKLETS - THREE (3) PER STUDENT DATA - TWO (2) PAGES ATTACHED GRAPH — ONE (1) PAGE ATTACHED 2 X 4 LOG-LOG CYCLE GRAPH PAPER - ONE (1) PAGE ATTACHED EXAMINATION MATERIAL SUPPLIED BY THE STUDENT: STUDENTS MAY BRING ANY MATERIALS THEY WISH INTO THE EXAMINATION INSTRUCTIONS TO STUDENTS: Students are prohibited from having mobile phones or any other device capable of communicating information (either verbal or written) in their possession during the examination NO NOTES MAY BE MADE DURING PERUSAL TIME SECTION A — BOTH QUESTIONS ARE TO BE ATTEMPTED SECTION B - ALL THREE (3) QUESTIONS ARE TO BE ATTEMPTED SECTION C - QUESTION 6 IS TO BE ATTEMPTED MARKS FOR EACH QUESTION ARE AS INDICATED ATTEMPT EACH SECTION IN A SEPARATE EXAMINATION BOOKLET THIS IS AN OPEN BOOK EXAMINATION THIS EXAMINATION PAPER MUST NOT BE REMOVED FROM THE EXAMINATION ROOM Queensland University of Technology W Gardens Point GUT Kelvin Grove GUT Carseldine l CEB523 ENVIRONMENTAL GEOTECHNOLOGY SEM 1 2005 SECTION A QUESTION 1 (30 MARKS) Explain the meaning and the significance of each of the following terms: Where relevant, provide a neat, labelled sketch to illustrate your answer. (a) Retardation, Dispersion and Advection. (6 MARKS) (b) Fractured rock, unconfined and confined aquifers and their significance to contaminant transport of chemicals. (4 MARKS) (c) Background, Incremental and Total Risk. Using a simple diagram show the concept of exposure ‘contaminant’ pathways for groundwater and atmospheric means from a toxic chemical dump. (6 MARKS) (d) ADI, LOAEL/NOAEL, RfDS, risk factors/slopes, Carcinogen and Acute Toxicity. (6 MARKS) (e) Name 10 notifiable activities under the EPAct? Using a simple flow chart and diagram describe how you would conduct a Phase 1 Investigation for a CATTLE dip site (both groundwater and soil). 9 (8 MARKS) (TOTAL 30 MARKS) QUESTION 2 (10 marks) Write brief notes to explain the meaning and the significance of each of the following terms: Where relevant, provide a neat, labelled sketch to illustrate your answer. (a) Potential acid sulphate soil. (b) Important factors affecting actual evapotranspiration. (c) Wilting point and Field capacity. (d) The difference between steady state and transient flow conditions. (e) Acid Sulfate Soil Indicators. (10 MARKS) (TOTAL 10 MARKS) CEB523T1.051 cont/... SECTION B 140 MARKS! This part of the exam consists of a series of questions concerning aspects of an investigation of a contaminated site. Over the last 10 years at this site, there have been surface spills and leakage from above ground storage tanks containing various chemicals including Toluene, DDT and Dieldrin. This is of concern because the site is to be redeveloped as a residential subdivision and because water from an aquifer below the site is used for irrigating commercial vegetable gardens about 500m from the site. Figure 1 (attached) shows a generalised soil and rock profile based on data from 10 boreholes including those at locations A, B and C, as shown on the longitudinal section. The soil profile is typically as follows: Surface Elevation, 100.00m 0.0m ~ 1.0m depth Silty sand, moist, loose to medium dense, with some organic matter. 1.0m — 5.0m depth Sand, fine to medium grained, generally with a trace of silty fines but also containing some lenses of clayey sand/sandy clay up to 1m thick. Medium dense. The water table depth varies but it is generally at about 2.5m depth. 5.0m — 10.0m depth Clayey siltstone, medium plasticity, moist, very stiff. Extremely weathered siltstone. Bedding planes dip at 30 degrees. Sub—vertical joints at 200 to 600mm spacing. Most joints appear to be infilled with silty clay to give a low permeability. 10.0m ~14.5m depth Coarse porous sandstone, very weak, moderately weathered. Particles grade from‘medium to coarse grained with negligible fines. 13.5m ~17.5m depth Claystone, dense, fine grained, horizontally bedded, slightly weathered. The widely spaced joints are clay infilled to give a very low permeability rock mass. Section B continues on the next page CEB523T1.051 cont/. .. Two piezometers have been installed at each of the locations, B and C shown on Figure l. The observed piezometric levels are as follows: LOCATION PIEZOMETRIC LEVEL B — screened from 1.0m to 5.0m depth 97 585m C - screened from 1.0m to 5.5m depth 97.425m B — screened from 10.0m to 14.5m depth 98.030m C - screened from 10.5rn to 14.5m depth 97.950m There are two groundwater wells, 500m beyond C, in a straight line from ABC. These are screened in the porous sandstone stratum and are supplying water for commercial vegetable gardens. The source of contamination at the Industrial Site was a series of above ground storage tanks and work areas between B and C. QUESTION 3 110! MARKS (a) Prepare a neat sketch of the soil and rock profile and label any aquifers, water tables, aquicludes or aquitards and indicate the directions of groundwater flow at the site. (b) Assuming the following, general orders of magnitude of the permeabilities and porosities of the strata, make a preliminary estimate of the rates of movement of the groundwater through the various strata and show your results on your sketch for Q2a. STRATUM EFFECTIVE POROSITY PERMEABILITY IN M/DAY Medium to fine sand 0.20 55 m/day Clayey siltstone 0.25 m/day 75 may 0.03 0.0005 m/day (impermeable) (10 MARKS) (TOTAL 10 MARKS) Section B continues on the next page CEB523T1.051 cont/. .. QUESTION 4 $10! MARKS The attached Table Q2 describes toxic, physical and chemical properties of the three contaminants, Dieldrin, DDT and Toluene. You are required to demonstrate your understanding of the significance of the relative values shown in the table by comparing the relative toxicity, transport and exposure and uptake of Dieldrin, DDT and Toluene at an Industrial Chemical plant site. Compare the relative toxicity, transport and exposure for the three contaminants at the Site, basing your assessment on the characteristics listed in the table. Please use the following headings for your discussion: a) Toxicity (b) Transport — through the surface, vadose zone and the aquifer. (c) Exposure and Uptake (10 MARKS) (TOTAL 10 MARKS) Section B continues on the next page CEB523T1.051 cont/... UESTIONS 20 MARKS The following table summarises the results of a constant discharge drawdown pump test that has been carried out to evaluate the hydraulic characteristics of the sandstone aquifer. Water has been pumped from the well at a constant discharge of 250 litres/min (350 m3/day) and the water level in a monitoring well, 10m from A has been recorded at intervals. The following table shows the drawdown of the potentiometric surface at the monitoring well as measured at a series of times after commencement of the test. mmsmflflnMME drawdown,m 0.355 0.427 0.494 0.563 0.655 0.723 0.841 (a) Prepare a neat labelled sketch of a cross section of the pump well showing all the important features. radius, m (b) What assumptions are made in the Theis method with respect to geometry and location of the well and the aquifer and the properties of the aquifer? (c) Use the Theis log—log curve matching procedure to estimate the transmissivity, storativity and permeability of the aquifer. Theis’s solution of the flow equation is plotted on the attached graph and similar scale blank log-log graph has been supplied. Use units of metres and days. ((1) Which is more accurate and reliable, pump tests or slug tests? Why? Explain the advantages of using Step Drawdown/ Recovery tests in aquifer testing. (e) Describe the terms cone of depression and drawdown. Use sketches to explain. (TOTAL 20 MARKS) CEB523T1.051 cont/... SECTION C QUESTION 6 $20) MARKS a. What are the three main design criteria for a compacted clay liner in a landfill? b. Describe the advantages and limitations of flexible-wall permeameter. (4 MARKS) 0. Consider typical laboratory compaction test results shown below. A; High Compactivc Erica‘s 0 Medium Cnmp-‘mfiwa— Effort 5 [3 Low flumpmctme Effort Ax. Ram Air Void-r H .C .9 U E .2: fi 3, 32‘ a Mutding Water Canter“ i Discuss the effects of roller type and mass on the dry unit weight and optimum moisture content variation in situ. ii Describe the significance of “ ry of optimums” and “wet of optimums” in compacting a clay liner. iii The following figure was obtained from a laboratory study on the variation of hydraulic conductivity as affected by compaction. Solid symbols correspond to compacted specimens with hydraulic conductivity S 1.0 x 10'7 cm/sec. Based on the results, it was suggested that the shaded area be used as the acceptable zone for compaction. Do you agree? Why? If you do not agree, explain how you are going to adjust the acceptable zone for compaction. 20 5;." 19 M g Zero air voids H 5/ 18 Line of E optimums D * OI) 1 .= 17 j C: 3 Acceptable zone for .. 3‘ hydraulic conductivity Q 16 ' ~ W 15 l l __l l i 4 l . __ _ I 8 10 12 14 l6 18 20 22 Molding water content ("/o) Section C continues on the next page CEB523T1.051 cont/. .. 7 iv Explain how you measure hydraulic conductivity of a clay liner in situ. (8 MARKS) d. Discuss the types and characteristics of geosynthetic clay liner. Describe the advantages of GCL as compared to clay liners. (3 MARKS) e. A 3m deep trench is being excavated in a saturated sand (ysm = 22 kN/m3) with an angle of internal friction of 40°. Bentonite slurry (y = 14 kN/m3) is being used to stabilise the trench. The ground water table outside the trench is located at a level 0.5 m below the ground surface. Calculate the required depth of bentonite slurry to obtain a factor of safety against failure of 1.5. What is the mobilised friction angle of the sand? (5 MARKS) (TOTAL 20 MARKS) END OF QUESTION PAPER CEB523T1.051 (i) wwwwwwwwwwm . C. . ‘ ._ 1% ,. . I H m .H ///////////// C A m 0 0 2 A “lldllll IIIIIIIII S I «I. H e H II t IIII I m d m “I n W m m H O m a y H 0 ll 2 S a C " t I e 0 l n " S Ill .1 0 W. C O H W y u D. 1 I. t H / a n .1. S I 1.1 I S W h m M C n / .1 I I . E S H n B Ill: 1,112.2}...1 I Iii-\hlulnullua-hl I a I .n \.\.\n.m....\.s.s.~....:~u Ir Surface Elevation FIGURE 1 E n S L m R T S U D W F O E L I F O R P K C O R D N A m 0 S CEB523T1.051 (ii) TABLE Q2: CHARACTERISTICS OF CONTAMINANTS (from TOXNET & USEPA IRIS sources) pRopERTY DIELDRIN TOLUENE oral chronic reference dose (acceptable daily intake) mg/kg 0.00005 mg/kg/day 0.0005 mg/kg/day 0.2 mg/kg/day body weight/day. reference concentration for 3 -- insufficient 0.00002 mg/L 0.001 mg/L evidence .of carcrnogenicity available insufficient 0.000002 mg/m3 0.0001 mg/m3 evidence .0? carcmogenicity available max. contaminant level for 0.00005 mg/L 0.002 mg/L 0.15 mg/L California 1 6 X1061“ Hg at 1.6X10'7 mm Hg at 250C 25 C 1 in 100,000 carcinogenic risk drinking water conc. l in 100,000 carcinogenic risk from inhalation exposure. Concentration in mg/m3 vapour pressure mm Hg 250C solubility in water 526 /L t mg/l 0.2 mg/L at 250 C 0.1 mg/L at 250 C errlgc a relative sorption to soil minerals 10004030003000 2.73 (low) 13 to 90 in fish(low to moderate) 5 .40 (very high) octanol/water partition log K0w 6.91 (very high) 3300 to 14500 in fish 600 to 84000 in fish (high - very high) (medium to very high) bioconcentration factor CEB523T1.051 (iii) 95:0 2:8 £2; oooow 3: 82 OS 2 w J J to IIL L fl 3 w _ a O.Ow CEBSZ3T1.051 (iv) 0000 F0 000 r00 «9:933 5 NS 850.0 0 r0000 5000.0 0_‘.0 00. r _\0.0,¥,.. sanaw u! umnpmmg CEB523T1.051 ...
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This note was uploaded on 04/26/2010 for the course EN 40 taught by Professor Mcgregor during the Two '10 term at Queensland Tech.

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CEB523-T1-S1-2005 - GUT Student Number Surname Given Name/s...

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