1.1 In this part of the publication, the fundamental principle and procedure for execution of the work have been dealt with. The essential requirements and precautions to be taken in respect of execution of all types and class of Electrical and Lightning Conductor works for ensuring safe, economical, durable and more practical use and applicable of electricity including prevention of fire hazards and protection of structures from lightning, have been incorporated.
1.2 This booklet shall be a guide to Engineers, Subordinates Officers, Contractors, in respect to preparation of estimates, drawing up schedule of works, execution of works and also settlement of additional item of works arising during execution.
Preparation of estimates and Schedule and Dealing with Schedule & NonSchedule items, prior to calling tender
2.1 While preparing the detailed estimate and the Schedule of Works for calling tenders, all items shall be so styled as to fall within the scope of items incorporated in the ‘Schedule of Rates’ hereafter called, the Schedule items, as far as possible. But where it is necessary to incorporate one or more items not covered by the ‘Schedule of Rates’, hereafter called Non-scheduled items, may be provided in the Schedule of Works for which the tender is to be called, provided that such items, incorporated in the Estimate, are technically sanctioned by the Superintending Engineer prior to calling of tender. During preparation of such estimates, discount available in the market should be considered.
Prior approval of SE in respect to Non-Scheduled items, for calling tender
Provided, always, in case where such items are in the estimate, technically sanctioned by the officer below the rank of the Superintending Engineer, the details of such items together with the analysis of rates and the complete schedule (in triplicate) shall be submitted to the Superintending Engineer for approval.
Value of Scheduled & Nonscheduled items to be allocated and have the approval of SE
2.2 Schedule of work containing one or more ‘Non-scheduled items’ shall not be accepted by an officer below the rank of the Superintending Engineer unless the approval of the Superintending Engineer is obtained. The estimated value of items of non-scheduled work and scheduled work in such cases shall be allocated while calling tender.
Correct Grouping of items, explained.
3.1 In no case, two or more scheduled items shall be combined. All items are to be stated (described) in such a manner that the correct bill of quantity and actual requirement of the department can be easily understood. An illustration given below will explain the correct procedure.
3.2 Incorrect procedure :
Laying UG cable size (25 sqmm to 225 sqmm) from X to Y laid direct in ground with necessary GI pipe protection as required – 1000 mtrs.
Here, it is not possible from the item, for the tenderer to assess what length of cable for each cross-section will be laid. As the cost of laying cable for sizes 25 sqmm to 225 sqmm varies according to light and heavy sections, it is not fair that a uniform rate shall apply.
3.3 The length and grade of GI pipe required for protection cannot be assessed. Thus, the cost of the item can not correctly be worked out which may lead to unfair competition. The requirements of the Department can hardly be accurately assessed by any tenderer.
'Such items must be avoided.
|(a) Laying 2 Core, 1.1 KV Grade PVC/A UG cable (size 50 sqmm to 95 sqmm) from X to Y laid direct in ground at an average depth of 0.75 mtr. below ground level in trench with single layer of bricks (8 Bricks/mtr.) protection on Top||800 meters|
|(b) Laying 2 Core, 1.1 KV Grade PVC/A UG cable (size 225 sqmm) from X to Y laid direct in ground at an average depth of 0.75 mtr. below ground level in trench with single layer of bricks (8 Bricks/mtr.) protection on Top||200 meters|
|(c) Providing 50 mm (2") GI pipe (ISI-Medium) protection for crossing roads, drain, vertical rise etc.||100meters|
Here, it is possible to assess the correct length and grade of GI pipe. Since the rate of laying UG cable of 50 to 95 sqmm is same, it is not objectionable to include both the cross-section of cables in one item
– 800 Metre
– 200 Metre
– 100 Metre
3.5 To be clear and precise, the items of works in the estimate, and schedule shall be adequately described, so that the requirement can be easily ascertained and that there is least possible ambiguity as to the quantity, quality and size etc.
3.6 In view of occurrence of time lag between preparation of estimate and receipt and sanction thereto, a provision of 5 % price escalation per annum be made in major estimates, so as to avoid preparation of revised estimates due to in the intervening period. The requisition authority is to be requested to take note of the price escalation clause and to include the additional cost to the estimate before according sanction if the time lag between submission of estimate and sanctioning thereof is more than a year.
4.1 For the purpose of execution of the works as per Terms of Contract incorporated in Form No. 2911, 2911(i) and 2911(ii), the Engineerin-charge of the work shall normally mean the Engineer-in-Charge in respect of the works within the limit of his power of acceptance.
Delegation of Power
4.2 An Executive Engineer may also delegate his power of the Engineer-in-Charge in writing to the Assistant Engineer in charge of the Sub-Division in respect of a particular work or all works exceeding their financial limit. The delegation of such power shall be intimated to the contractor also.
Function of AE on behalf of the Engineer-inCharge
4.3 Assistant Engineer shall, however, in all works executed within their jurisdiction, shall supervise, issue day to day instructions to the contractor in writing with copies of such correspondences to the Executive Engineer, even when these officers are not delegated with the powers of the Engineer-in Charge.
Documents to be furnished to AE
5.1 Assistant Engineer is to be provided with the copies of the sanctioned estimate, Plans, copy of Administrative approval, Allotments of funds, complete tender documents and all copies of correspondences between the Executive Engineer and the contractor. The Executive Engineer shall take steps so that these clauses are properly implemented.
Issue of Work Order to Contractor
5.2 No work shall be allowed to be commenced by a contractor unless his tender is accepted and the work order is issued by the appropriate authority.
Possession of Electrical Supervisor's Certificate, is a condition
6.1 It is obligatory under the IE Rules, that all Electrical Installation works shall be executed under qualified Electrical Supervisor holding Electrical Supervisor's Certificate of Competency granted by the State Licensing Board. This is also an important condition on which the contractor has been enlisted in the Public Works Department by the Government. \
Reference to Clause to satisfy above condition
6.2 Therefore, in order to execute the work by skilled and qualified workmen under the proper guidance and direct supervision of such a qualified Electrical Supervision of Engineer, the procedure as stated in Clause 6.3 be shall adopted.
Introduction of a statement and its submission with WB From No. 2911, 2911(i) or 2911(ii)
6.3 While submitting tender including duplicate or more copies of Tender Form for acceptance by the Assistant Engineer, the Executive Engineer or the Superintending Engineer, as the case may be, the contractor shall submit a statement as below, with each copy of WB Form No. 2911, 2911(i) or 2911(ii) to the tender accepting authority. The statement shall contain the necessary information and declaration by the Contractor as well as by his Supervisor appointed to execute and supervise the work.
(a) Name of work.
(b) Name of the Electrical Engineer / Supervisor.
(c) Qualification (i.e., the parts in which the Electrical Supervisor's Certificate of Competency has been issued by the Licensing Board).
(d) Registration No. of Supervisor’s Certificate.
(e) Next date of renewal of Supervisor's Certificate.
(f) Contractor's License No. etc.
Licensed Supervisor / Engineer to represent Contractor and to apply for layout
6.4 The contractor shall be represented by his Supervisor or Engineer, holding Electrical Supervisor's Certificate of Competency granted by Licensing Board, West Bengal, for supervision and execution of the work. Such Supervisor or Engineer of the Contractor shall apply to the Assistant Engineer-in Charge of the work for layout immediately on the issue of the acceptance of the tender.
Fixation of date and time for layout where contractors fails to respond
6.5 No layout shall be given by any Department officer, other than to a qualified licensed Engineer or Supervisor as stated above. If the Contractors fail to be represented by a Supervisor in the manner stated above or does not immediately apply for layout, the date and time of layout shall be fixed by the Departmental Officer and intimated to the contractor, but no extension of time shall be granted to the contractor for such delay in commencement of work, unless there is sufficient cognizant reason, which shall however be recorded in writing by the officer granting the extension of time.
Supervisor's signature in MB
6.6 While recording measurements, the MB shall be signed by the Contractor's Engineer or Supervisor, with his License No. noted therein, as a token not only of the acceptance of measurement but also of the execution of the work under his supervision.
6.7 No bill shall be paid by an Executive Engineer unless the Contractor's Supervisor signs the MB as stated above.
Where delay in signing MB by Contractor occurs
6.8 In case of delay on the part of the contractor to sign the MB the measurement of the work shall not however be deferred. The bill may however be drawn and the amount of the passed bill may be debited to Deposit schedule and credited against the work.
Acting against declining to sign MB
6.9 The payment in such case shall only be made on receipt of the explanation from the contractor. Frequent commission on the part of the contractor to sign the MB, shall be reported to the Superintending Engineer for administrative action.
Step against Substandard workmanship is as essential, as the work
7.1 The workmanship is to be given the utmost importance. Good and skilled workmanship is an essential requirement for compliance without which the work shall be dismantled and re-done as directed by him. This shall, however, be decided during the progress of the work or within one month from the date of completion of the work. This, however, shall not be prejudiced to the power of rectification of defective or rejective work in terms of Contracts in WB Form No. 2911, 2911(i) and 2911(ii), as re-embodied in clauses 3, and other relevant rules made there under.
Removal of the bad Work-man
7.2 Any workman, who is in the opinion of the Engineer-officers, not efficient or otherwise unsuitable for any reason whatsoever, shall immediately be removed by the contractor, from site of work, on receipt of the intimation in wiring by the Engineer-in-Charge. The decision of the Engineer-in-Charge shall be final.
Programme and commencement of work, exceeding Rs. 50,000/-
8.1 In the case of works, exceeding the estimated values of Rs. 50,000/-, the contractor shall draw out the programme for execution of the work in consultation with Assistant Engineer and shall submit 4 (four) copies of such programme to the Executive Engineer for approval within 5 (five) days from the date of issue of the work order.
Approval of work- programme by the Engineer-inCharge
8.2 The Executive Engineer on receipt of the programme, shall approve, amend or reject the programme and promptly send one copy of the final programme to the contractor, two copies to the Assistant Engineer and retain one copy to his office.
Programme and layout of work of Rs. 50,000/- or below
9.1 In the case of work, estimated value of which is Rs. 50,000/- or less, the programme of execution of the work shall be approved and finalized by the Assistant Engineer or in the manner prescribed in Clause 8.2, but the time taken for approval of programme of the work shall not be a cause of extension of time. It is expected that the contractor, on receipt of the acceptance of such work, will send his Supervisor to the Assistant Engineer or to the Sub-Assistant Engineer for layout and programme to execute the work expeditiously.
Compliance with Acts and Rules
All Electrical works (both internal and External) shall be carried out in accordance with the provision of :
(i) Indian Electricity Act 1910 (ii) Indian Electricity Rule 1956 and Regulations framed thereunder (iii)The Electricity Act 2003 (iv) The rules and bye-laws of the Local Electricity Supply Authorities
9.2 All Electrical and LC Installation works shall also comply with the General Specifications and shall be subject in all respects to the approval and entire satisfaction of the Engineer-in-Charge.
Failure to comply Rules & Suspension of Work
9.3 Failure on the part of the Contractor to comply with the provision of Clauses 9.1 & 9.2 may render to the suspension of the contractor’s work or any other action as deemed fit. The decision of the Superintending Engineer, in this respect, shall be final.
Use approved materials only
10.1 (a) Materials which are not in the List of Approved Materials of this Department shall not be used in the work by the contractor. No work below the approved specification shall be executed. All materials, not otherwise specified, shall be in accordance with the latest appropriate Indian Standard Specifications where such exist.
Use approved materials only
10.1 (b) If not mentioned otherwise in the items themselves all materials including fittings shall confirm to standard laid down by the ISI and bear ISI mark where such standardisation has been made. All other materials must be of best quality conforming to the standard laid down by the BIS and being approved by the Engineer-in-Charge. Under very special circumstances, materials standardised by BIS with ISI mark but not bearing ISI mark may be accepted with prior approval of Engineer-in-Charge with reduction by 20 %.
Rejection of Sub- standard materials and their removal from site
10.2 All materials brought to site shall be to the approval of Engineer-inCharge. Materials, which are Sub-standard, shall be rejected. The sub-standard materials brought to site or used in the work shall be removed by the contractor within 24 hours on receipt of the notice to that effect from the Engineer-officer of the Department.
Appeal by the Contractor in respect to materials
10.3 An appeal may, however, be made by the contractor against such order to the next higher authority, where there is a ground of erroneous decision or any other rightful cause. But the order of the Engineer-officer in respect to clause 10.2, shall be binding upon the contractor until revision of the order is made by the higher authority.
Contractor's appeal to SE to consider the cases involving loss
10.4 The final appellate authority, in respect to Specification of works and materials, shall be Superintending Engineer. In case of complicated matter involving (a) financial loss to the Government or the contractor or (b) retardation of the progress of the work, the contractor may prefer an appeal direct to the Superintending Engineer.
10.5 A copy of application in such cases shall be submitted by the contractor to the Executive Engineer and the Assistant Engineer and due acknowledgement shall be kept by the contractor.
SE’s order in respect to the material& work is final
10.6 The orders of the Superintending Engineer shall be binding upon the Contractor and Department, in the case of such appeal arising out of the technical aspect during the execution of work.
Contractor shall be custodian and shall store, stack and guard the Govt. materials
11.1 All materials, which are to be supplied by the Government to the contractor, shall be handed over by the Department in the manner prescribed in Clause 11.6, expeditiously according to the settled programme of the work. The contractor shall, therefore, on receipt of the materials properly store and stack in the manner approved by the Department Officer at the site store. The contractor shall be custodian of such materials and shall be responsible for any loss or damage to the materials.
Inspection of Site- store
11.2 Departmental Officers may inspect the materials stored at the contractors’ store at site during the inspection work.
Maintaining account of materials and return of excess quantity
11.3 The contractor shall maintain day-to-day account of the receipt and the issue of Govt. materials. On completion of the work the said account shall be submitted to the Departmental measuring-officer and the balance materials are to be returned to the Department, in the manner as directed.
No materials to be removed by Contractor
11.4 No materials issued to the contractor shall be removed or utilised in any other work than for which it has been indented, without the written order of the Executive Engineer and Assistant Engineer.
Short and excess of materials, occurring under contractor's custody
11.5 If at any time, the quantity of Departmental materials is found short or excess at the contractor's custody by the inspection officer, the matter shall forthwith be reported to the Engineer-in-Charge, who shall expeditiously deal with the matter according to its merit.
Different Categories of Departmental materials & procedure of their issue to Contractor
11.6 Issue of Departmental materials may of two categories :
(A) Materials for which the values are to be recovered from contractor as per tender agreement or otherwise.
(B) Materials which are issued direct to work (in respect of items whose cost shall not be recovered from contractor, as per Terms of Contract).
For formalities of Category (A), the materials shall be issued in PWD Challan Form (WB Form No. 28). 1st copy of such challan shall be attached with the next bill of the contractor for realisation of cost. 2nd copy shall be retained with the office copy of the bill at the Sub-Division and 3rd copy shall be retained for Site Account. 4th copy for the contract and the 5th copy shall be retained for the challan book.
For formalities of Category (B), 5 copies of Challan or HR as stated in sub-para above shall be prepared by marking “Value not to be recovered”.
Contractor's responsibility for materials issued
11.7 The materials issued to the Contractor, whatever be their category thereof, the contractor shall remain responsible for their proper storage, safe custody and proper utilization of such materials. The contractor shall also remain responsible for any damages or loss of such materials.
Return of Scrap or excess materials issued as per Clause 11.6 (B)
11.8 The excess materials including cut lengths of cable, conductors etc. issued to the contractor vide clause 11.6 (B), shall be returned in good condition to the Engineer-Officer, or as directed, through proper challan in quadruplicate after the completion of the works.
Misuse of materials and the recovery of cost from contractor
11.9 The contractor shall use the Departmental materials as stated in Clause 11.6 (B), cautiously and judiciously so that the minimum quantity is wasted or reduced to scrap. In cases where the scraps, or wasted, are considered in the opinion of the Engineer-officer, materials to be above normal, the value of the excess quantity (after allowing the normal wastage) shall be deducted from the contractors bill. The decision of the Engineer-in-Charge, in such cases, shall be final and binding on the contractor.
Disposal of surplus materials
11.10 All surplus materials shall quickly be disposed of either by transferring to stock account of the store (after obtaining prior orders of the Superintending Engineer) or to other work direct.
Return of dismantled materials by the Contractor
11.11 Dismantled materials (both serviceable and unserviceable) shall be sorted, tested and handed over to the Departmental Officer by the contractor in the manner as decided by the Assistant Engineer.
Recovery of rent or other charges for use of T & P etc. from Contractor
12.1 The contractor may use the T & P and other Govt. testing Instruments providing they are available and permitted by the Engineer-in-Charge. The rent or other charge for the use of such T & P shall be realized from the contractor's bill. Normally the insulation Testing Megger shall not be issued to the contractor by the Department.
Clearance of site
13.1 The contractor shall clear the site of work and the whole site shall be left clean and tidy to the satisfaction of the Engineer-Officer, within the date of completion of work.
Incomplete work due to nonclearance of Site
13.2 Failure on the part of the contractor to clear the site, as stated in the aforesaid clauses, shall be treated as the work is incomplete, even though the work for which the contract executed, has been completed and work is in beneficial use
Charges for clearance of site
13.3 The cost of restoring the site of work will be realized by the Engineer-in-Charge from the contractor's bill after a due notice is served on the contractor.
Procedure to be followed on receipt of Administrative Approval of project
14.1 The following procedures shall be adopted by the Departmental Officer on receipt of the administrative approval of the project, as well as on the receipt of the estimate from the Sponsoring Department, in respect of the work relating to OH Distribution and UG cable.
Submission of Detailed Estimate & Plan for Technical Sanction
14.2 Project and route survey map in the scale as deemed convenient shall be prepared. The position of the pillar box etc. and all other equipments shall be marked on the plan which shall be placed before the appropriate Departmental Officer along with the detailed estimate for technical sanction.
Action to be taken to procure materials after obtaining Technical Sanction
14.3 The list of the materials (with quantity) which are to be procured by the Department shall be drawn up on receipt of the technical sanction of the estimate or with the approval of the Superintending Engineer. Steps shall be taken for procurement of materials, either by calling tender from the market or direct from the Central Store. Arrangements shall be made for proper storage of materials including guarding.
Preparation of Schedule with specification of materials
14.4 The Schedule for the execution of works and calling tender from the appropriate class of the contractor shall be prepared. The grade and specification of materials shall be invariably specified in the Schedule of work.
Survey, Estimates for OH line Distribution & UG cable works to be done by the Electrical Planning Division / Circle
14.5 When the route length of OH Distribution network exceeds one km., survey, drawing up the list of the materials, Schedule for execution of work shall be done by the Executive Engineer, Planning Electrical Division / circle. When the route length of OH Distribution falls below 1 km., such action shall be taken by the working Division. The same procedure shall also apply in case of UG cable and the procedure shall also apply in case of UG cable and the project estimate of elec. works when the value of such work exceed Rupees 1.0 (one) lac.
Importance of engaging skilled & experienced workmen to avoid error or ommission
15.1 Installation, i.e., erection of Transformers, H.T. & L.T. Switchgears, Laying of UG cables, developing Sub-station etc. require highly skilled, experienced workmen. Only those personnel, who are fully conversant with such job, shall be allowed to handle works. Slight error or omission may result in serious accident or future troubles.
It must be remembered that the choice of materials, layout of the work and skill and experiences all combine to determine the character and efficiency of the installation.
Gradation of materials and their choice depends on the merit of case
16.1 Accessories and materials for electrical works, with special reference to UG, OH and Internal Installations have been classified into two grades, viz., Grade I & II. The gradation has been made in consideration to the quality. The, materials, as Grade I, are comparatively superior and higher in price. The choice of grade rests with Engineer Officer in consideration to the merit of case.
All materials shall be of highest grade of their respective kind and, as far as possible, comply with the specifications laid down in separate book.
Basis of rates worked out & provided in the Schedule
16.2 The rates provided in the Schedule (both for materials and item of works) have been worked out on the basis of analysis of the current market study. But it is generally accepted that the fixing of price is not strictly possible due to market variation. While preparing Schedule of rates an ambit of minor marginal adjustment to accommodate reasonable fluctuation has been taken into account.
Scope of Rules and Sub-rules made
17.1 All rules and sub-rules made hereunder, shall apply mutadismutandis to the context of the tender agreement made in either of the Form No. WB Form No. 2911, 2911(i) and 2911(ii).
Reference to SE in case of doubt
17.2 In case of doubt, ambiguity that may arise, reference shall be made to the Superintending Engineer and his decision shall be final and binding.
18.0 Instructions for preparation of Estimates :
Classes of estimates – Major and Minor Works
18.1 The estimates are of two classes, viz., Major and Minor Works relating to either Original or Repair works. This has been amply dealt with in the PWD code, Financial Rule, WAD Manual etc. of the Government. In following clauses are dealt with so as to facilitate the checking of the estimates in Divisional and Circle Officers and to minimize the scope of Audit Objection.
18.2 Detailed estimate amounting to Rs. 20 lacs and above should be referred to SE, Electrical Planning & Monitoring Circle for preparation.
18.3 Any changes in estimate if necessary, during execution of work should be referred to the SE, Electrical Planning & Monitoring Circle for obtaining opinion in writing.
Allocation of cost in Major Work estimates
18.4 In all estimates there shall be (i) Reference (ii) Report (iii) Details of the items of works. In major works estimate, a board sheet, showing allocation of costs of the various Sub-heads or class of work, shall also be furnished.
Inclusion of cost in reference of letter
18.5 The reference shall also be include the correct appropriate indication of the letter of memorandum requisitioning the work or project to the Public Works Department It is incorrect to cite the reference between the Assistant Engineer and the Executive Engineer, as reference in the estimate.
Report prefacing an estimate shall fully explain Physical & Technical aspects of work
18.6 The report prefacing an estimate shall be (1) self Contained (2) self-explanatory in respect to the physical and technical aspect of the project. The works, which are not specifically requisitioned by the sponsoring authority but considered essential in order to have a sound and comprehensive scheme, shall be included in the estimate. Such work shall be provided under separate Sub-head and the cost allocation in the abstract of the estimate. Explanatory note with justification for incorporation of such work shall also be amply stated in the report.
Information to be incorporated in the report prefacing an estimate
18.7 When it is necessary to consult the officer of the sponsoring department the correct designation of such officer, the date of consultation and the designation of the PWD officer who was present in the consultation shall be indicated in the report. Where conference are held between officer of PWD and other department, reference of the minutes or proceeding shall also be mentioned.
Estimate of rough cost to be sent to Sponsoring Deptt. for Administrative Approval at preliminary stage
18.8 At the preliminary stage an estimate of rough cost for major works may be prepared for submission to the Sponsoring department for obtaining Administrative Approval of the Government. The report in such estimate shall clearly indicate the physical aspect of the work, so that no doubt or misconception may arise regarding the provisions made to meet the requirements of the sponsoring department.
Detailed estimate to be prepared on receipt of Administrative approval. Such estimate to be submitted before completion the work
18.9 Detailed estimate on the basis of the rough estimate shall only be made on receipt of the Administrative Approval or signal to go ahead from the competent authority. Standing rules and orders demand that detailed estimate shall be technically sanctioned by the Appropriate Authority before the financial liability is incurred. It is also not regular to submit the detailed estimate for technical sanction after the Work is completed to the Appropriate Authority..
Submission of detailed estimate before acceptance of tender for technical sanction
It is, therefore, instructed that the detailed estimate shall be prepared and submitted to the Appropriate Authority for Technical Sanction before the acceptance of tender and incurring any expenditure.
18.10 While preparing a revised estimate, a statement shall be appended with such estimate giving the following information :
(i) Quantity of Each item in Original Estimate and the Revised Estimate.
(ii) New items of works with quantity, incorporated in the Revised Estimate.
Explanatory notes in the report with reasons of revision, and the reference of the Administrative Approval of the project shall also be mentioned. Information to be included in the revised estimate
Submission of Plans with estimate Quality control
18.11 All estimates shall accompany plans for residential building and non-residential buildings.
19.0 Instructions for controlling of quality of materials used :
19.1 Performance of materials either received from Central Store or used directly through the working contractors should directly be reported to SE, Electrical Resources Circle, PWD with copies to his concerned higher officer.
19.2 After receiving such report necessary action should be taken up with the manufacturer for remedial action.
20.0 Some useful formulae and other technical information etc. for the design practice have been incorporated in the ‘Annexure’ of this book.
20.1 In view of excessive price rise of Galvanized Iron pipes, it has been decided that for almost all sorts of EI works and LC Installation works PWD approved (ISI-medium) GI pipes will be used and the schedule of rates have been prepared with such pipes. TATA make GI pipes have been considered as Earth Electrodes. However, TATA make GI pipes can also be used under special circumstances, where necessary, with the approval of concerned Superintending Engineer.
20.2 The Price of the cable and IC switch (Grade-1) with HRC fuse will be as per prevailing list price of the manufacturers and the rates given in the schedule book, in this context, are only for general guidance in preparation of estimate.