.Collection of data; operation of the feature and also the issues' impact .Collation, analysis, and interpretation of data; on the cost of the design, construction, and operation and and maintenance. Critical issuesshould be emphasized .Preparation of findings. to make certain they are thoroughly scrutinized and evaluated. ENGINEERING GEOLOG,y EVALUATIONS Throughout the entire process of arriving at a deci- The impact of the geologic considerations and their sion or conclusion, the engineering geologist must ex- specific issuesupon the propo~ied engineering works ercise sound judgment. A discussion of each issue and must be evaluated throughout the engineering geol- its evaluation, including the data required to reach ogy program. Conclusions, decisions, and recommen- the conclusion should be documented in the "Geo- dations to address these issues must be provided technical Considerations" portions of any geologic re- during interim data submittals and in the final engi- port. The amount of detail of the discussion of ally neering geology report. To accomplish this, those rel- issue generally will depend upon its criticality and the evant geologic issueswhich must be addressed during type of the engineering geology report under prep- the engineering geology progr:im must be identified. aration. Individual discussion of each issue will ensure A convenient way to approach the identification and that relevant issues have been identified and ad- selection of issuesis to consider :separatelythe geologic dressed, are subsequently given proper consideration considerations groups on a site'-by-siteand structure- for design concepts and constructability, and are ap- by-structure basis. This should be done by: (I) refer- propriately monitored during construction and ring to the checklist of common issues in chapter 6; (2) discussing the program with involved parties; (3) operation. seeking the assistanceof experienced engineering ge- ologists and other professionals; and (4) reviewing and BIBLIOGRAPHY studying similar case histories. [ 1] Glossaryof Geology,American Geological Institute The issues should be categorized as to their relative third edition, American Geological Institute, Falls importance for a safe and economical design, proper Church, VA., 1987, page 788.
4
ENGINEERINGGEOLOGY
3. Document the investigatjion program on the following programs require much thought and dis- ACER Field Exploration JR.equestform; cussion. A phasedprogram is usually the most efficient and economical. The rationale for any exploration 4. Prepare transmittal memorandums; should be documented so that all understand the use and value of the data. The TDP requires a Technical 5. Inform other representatiives of field inquiries Memorandum (formerly the Engineering Geology Re- and of any actions taken. .'This may require dis- view Memorandum) to document these data and cussion and decisions by the group; known conditions. Additional exploration should be dependent on the results of the earlier explorations 6. Monitor the exploration program; and any corresponding changes in design concepts. It is very important that the field geologist have full in- 7. Prepare memorandums Dlodifying original in- put into any stage of the exploration program and vestigation program; and that he or she concur by initialling (or authorizing their initials) on the fInal program, as concurring, on 8. Assure that data reports are distributed. Bureau of Reclamation Form 7-2145, "ACER Field Exploration Request." It should be emphasized that Other members of the team are responsible for no- the team geologists' responsibilities do not end after tifying the coordinator of any inquiries, discussions, formulation of the initial exploration program. problems, or information received from field Most schedules are based on political decisions and personnel. are certainly budget oriented. Therefore, our data The initial meeting of the Exploration Team should collection mayor may not be allowed adequate time be held at the feature site. It is highly desirable that for the amount of data specifically required. The Ex- the team meet at the site with field geologists and ploration Team must make a reasonable evaluation of materials specialists who will be performing the in- time required to collect these data and make the nec- vestigations before the 'program is formulated. It is essary adjustments that will accommodate both the very important that the investigation program be sys- project and the Denver Office. Team members must tematically thought out and rationalized. For this rea- realize that .commitments should be met, and they son "on-the-spot" or hastily derived investigations should not make a commitment that can't be met. programs should be avoided. Prior to this meeting, If scheduling problems arise, they should be referred the field geologist should have become very familiar to the PMT. This team has the authority to address with the site geology and antici,pated geologic design schedule changes or reduce the program. They also and construction consideration:s. Much of the initial realize that when a program is reduced, the degree exploration program will be based on the field geol- of risk increases. ogist's knowledge of local geologic conditions. It can be of great value if the field geologist prepares a pre- Other important duties of the field geologist, as a liminary or recommended explolration program based member of the Exploration Team, include the sub- on his knowledge of the area. It is recommended that mittal of interim data, interpretation of data, com- the preliminary program be distributed to Explora- municating schedule or program problems and tion Team members prior to the site visit. The pro- completion, recommending modifications to the ex- gram should attempt to answc~rboth geologic and ploration program, and preparation of the Geologic geotechnical concerns. Although the program may Design Data Report. The Geologic Design Data Re- not be used in its entirety, it doe~ioffer a starting point. port serves to document the data collection and re- By the time the program is finalized, the Exploration suits. These data can be adjusted and supplemented Team should be able to justify fully all aspectsof the as needed. Just how these data are to be formulated program. Additional coordinat:ion meetings will be and used should be clearly defined prior to issuance held as necessaryduring progr.~ssof the program to of the ACER Field Exploration Request. resolve problems and make required modifications. INTERPRETIVE GEOLOGIC DATA AND The goal of the exploratory or investigation program PRESENTATION IN REPORTS AND is to prioritize and produce the amount of data re- SPECIFICATIONS quired for that level of study or design. These data are to be obtained in the most efficient manner and In an effort to improve the overall quality of Bureau at an economical cost. The team then transforms these of Reclamation specifications and reduce construction data into a report or the specifications in the most changesand claims, the Total Design Processcalls for efficient manner possible. the inclusion of geologic information that conveys both the known and anticipated geologic conditions. No attempt should be made to formulate an all-inclu- To accomplish this, accurate and timely data and inter- sive fiml program while in the field. The initial and pretations of these data must be presented. Design
6
ENGINEERING GEOLOGY
Table 3-1. -Geologic Milestones and Responsibility.
I I I NO WORK I None
1
1 Sched 1 None
START
TM (Technical Memorandum) ! Exploration Team Members. I I ACER Field Exploration Request(s) : Principal Geologist with team I : approval. Concept : Prelimiinary Ongoing Submittals : Field Geologist. ! Geolog~c Design Data Report(s) : Field Geologist with approval i by Principal Geologist. i Geologic Design Data Review ! Principal Geologist. : Memorandum(s) : Engineering Geology Considerations for : Principal Geologist. I ! Conceptual Design TM I I I CONCEPTC I
: Final {;eologic Design Data Report Field Geologist. Design ! Geologic Design Data Review Principal Geologist. : Memorandum : Draft Engineering Geology Considerations Principal Geologist. : for Design and Construction TM I DESIGNC I I ! Supple'ments to Geologic Design Data ! Field Geologist. Draft : Report Spec : Specifications Paragraphs and Drawings i Principal Geologist. : Final Jt:ngineering Geology Considerations : Principal Geologist. I ! for Design and Construction TM SPECD I I Review ! ! Revie\'1' spec paragraphs and drawings Principal and Field Geologists. REVIEWC I I I I : Principal Geologist. Review of Specifications I Revise Specifications Drawings and Paragraphs I Geology Division/Branch Signed through Approved (anytime ! Chief. from SPECD to SPECB)
SPECB
Book : Geologic Requirements During ! Principal Geologist. : Construction Memorandum pre (at least: two months prior to AWARDC) I I BOOKC I
8
ENGINEERING GEOLOGY
Table 3-2. -Required Action by Geologic Staff.
Flags and Action required by Geology stages I I NO WORK ! None officially. However, if geologic map of feature is not available, field geologist could start : mapping if approximate alignment or location is shown. Also, compile, review, and : summarize available data. I
Field geologist provides scheduling information to Project Management Team. Site mapping, Sched data revielfi.
START I i Site mapping and preliminary interpretations. Field geologist proposes explorations. : Design and Exploration Teams formed. : Site visit(s). : Geologic exploration program(s) developed and ACER Exploration Request(s) and TM Concept : completed. ! Geologic exploration program monitored, revised, or added to. : Periodic formal or informal data submittals. : Interim geologic data reviewed and provided to design team. : Geologic Design Data Report submitted, reviewed, and approved. i Documentation of geologic design and construction considerations (TM). CONCEPTC ! Geologic exploration program monitored and revised as necessary. I Identification of additional data needs. Design i Geologic Design Data Report supplemented (if required). i Geologic datcl reviewed, additional analysis. i Input to design concepts and parameters. ! Documentation of geologic design and construction considerations (Draft TM). I DESIGNC I I 1 Prepare spec paragraphs and drawings. Finalize geologic design and Draft : constructi,on considerations. Spec : Furnish spec paragraphs and drawing to coordinating design branch. : Signed through technical approval. I I SPECG* ~ SPECD~ ,
Review ! Review spec paragraphs and drawings; review all paragraphs, not just geology.
REVI EWC
Final Revise specifications paragraphs and drawings if necessary. Agree upon geologic requirements during construction. Spec
SPECB Book-Pre :Supplements to specifications. :Document geologic requirements for construction. 1 BOOKC
10
ENGINEERINGGEOLOGY
as aerial mapping done by Federal agencies,primarily Directories within U .5. Department of the Interior. A similar of- fice is operated by the U .5. Department of Agricul- ture in Salt Lake City, Utah. Several other sourcesare A partial list of directories such as Directory of Geoscience referenced in the Engineering Geology Field Manual, Departments, Worldwide Directory of National Earth-Sci- with annotations as to coverage, including National ence Agencies, Information Resources in the United States- Oceanic and Atmospheric Administration (NOAA), Geosciences and Oceanography, Industrial Research Labo- the National Archives, Bureau of Land Management, ratories, Government Research Centers Directory, and and the Remote Sensing Section (D-1542), Denver Geothermal World Directory, provides information about Office. locating names and addresses to use as contact points.
Data Centers Computer data bases Other specializeddata centers can be accessed.These include the National Geophysical and Solar-Terres- These machine-readable files index several thousand trial Data Center for earthquake data, Goodyear Aer- journals, books, conference papers, dissertations, ospace Corporation, Side Look.ing Airborne Radar maps, government publications, and technical reports. (SLAR) Imagery Depository, and the Defense Map- While the primary data bases for geologic informa- tion, such as GEOREF and GEOARCHIVE, should ping Agency. be accessed,many other data bases contain relevant Public Utility Companies information and should not be overlooked, such as NTIS, COMPENDEX, TRIS, NWWA, and Disser- These companies may retain studies done during site tation Abstracts. feasibility investigations. The Directory of Electric util- ities is a good source of addressesfor these companies. By allowing keyword searching, accessing titles, ab- stracts, and indexing terms, this method of searching METHODS OF TAPPING THESE is both more comprehensive and more efficient than SOURCE~i manual searching.
Libraries SUMMARY Most of the materials discussec(in this chapter are available in libraries. Give special attention to unique The geologist who makes efficient use of these exist- collections such as the Bureau of Reclamation, USGS, ing data sources will be in a better position to make Corps of Engineers, State libraries, university sources, good use of his field time. Tables which list contact and the depository system. U sing interlibrary loan to points, such as those for State geological surveys and accessmaterials not available lacally can expand the Fe.deralagencies, will speed up the information gath- geologist's scope considerably. enng process.
14
ENGINEERINGGEOLOGY
I. Bedrock units.- Traceab..~ geologic units of 4. Response to natural surface and near-surface similar physical and engineering properties should processes(e.g., raveling, gullying, massmovement). be identified as described, including: OTHER PERTINENT DATA a. Identification as to rock type (e.g., granite, sandstone, mica schist). Relative age and, where Include laboratory determinations of engineering possible, correlation with named formations. properties of surficial deposits and bedrock.
b. Physical characteristics (e.g., color; texture; Provide black and white photographs of representa- grain size; nature of stratification, bedding, fol- tive or particular geologic conditions, all drill hole iation or schistosity; hardness; and chemical fea- core, samples, and test pits and color photographs or tures such as calcareousor siliceous cementation; transparencies if appropriate or desired. concretions, mineral deposits, alteration other than weathering). Summarize data from remote sensing and geophysical surveys (seismic, resistivity), if performed and cOrre- c. Distribution and dimensional characteristics late with other geologic information. (e.g., thickness, outcrop breadth, areal extent). Run appropriate borehole geophysical logs in drill 2. Distribution and extent of weathering and al- holes and other appropriate surveys to delineate sub- ~~!!Q!!:-Weathering should. be divided into cat- surface conditions. egones that reflect definable physical changes in the rock mass due to weathering. Significant dif- Describe past, present, and possible future petroleum, ferences should be identified and weathering pro- water, and mineral extraction operations in the files developed. vicinity. 3. Structural features.-Bedding joints, foliation Describe investigations undertaken to ascertain geo- joints, joints, contacts, shear and fault zones, folds, logic conditions which may affect construction meth- zonesof contortion or crushing are to be described ods such as boulders, marshes, drilling conditions, in terms of the following: stability of grout or footing holes, ground tempera- tures, and gases. a. Occurrence and distribution. Map land uses,particularly along linear features such b. Orientation and changes in attitude. as canals, transmission lines, distribution systems,and highways. c. Dimensional characteristics (e.g., width, spac- ing, continuity). Corrosion surveys should be considered for all Rec- lalrn\.tion distribution systems,including pipelines, aq- d. Physical characteristics and their effect upon ueducts, discharge lines, and siphons, in addition to the rock mass(describe the conditions of planar power /pumping plants and tunnels. surfaces, such as openness, roughness, waviness of surfaces, striations, mineralization, alteration, GROUND-WATER DATA COLLECTION and infillings or healing). To describe investigations of ground-water conditions, e. Statistical evaluations of distribution, orien- note seeps, water levels or piezometric surfaces and tation, and physical characteristics. record their seasonal fluctuation, the occurrence of unconfined and confined aquifers, potential seepage, f. Relative ages (where pertinent). water-producing capabilities, chemistry, and ground subsidence. The following checklist may be useful as g. Specific features of shears or faults (e.g., de- a general guide for descriptions: scription of composition of the fault, zones of gouge and breccia, healing, displacement direc- I. Distribution, occurrence, and relationship to to- tions and amounts, attitude of striations or slick- pography (e.g., streams, ponds, swamps, springs, ensides, relative age of movement(s ]). seeps,subsurface basins).
h. Prepare accurate and complete logs of explo- 2. Existence of confined and unconfined aquifers rations using terminology consistent with the and relationship to geologic features (e.g., imper- narratives (Chapters 4 and 5 of PI, EGFM). Give vious and pervious strata, fractures, faults). consideration to appropriate indexes (e.g., RQD tRock Quality Designation], Hardness). 3. Recharge sources and permanence.
16