Case study 04 / 10Engineering workIn progress

Design-versus-cost review for 28 locations

A repeatable review pipeline instead of 28 manual checks. Before construction, survey shapefiles, CAD drawings and cost estimates for 28 locations had to agree. Checking that by eye, 28 times, over estimates of about 40 sheets each, is where mistakes hide.

At a glance

28locations with review minutes
121items for the designers to confirm
172unit-price findings ranked high / medium / low
4most serious findings re-verified against the original source files
Period
September 2026
Role
Member of the supervision team; reviewed the designs against the cost estimates and built the review tooling with AI coding agents
Status
In progress — minutes awaiting final sign-off
Links
Not public
Design review: DED drawings and survey versus bill of quantities Per-location review that matches survey shapefiles and DED drawings against the bill of quantities per channel and structure, and ends in review minutes (Berita Acara). Design review: DED (SHP + DWG) vs bill of quantities (RAB) Per location, per channel and per structure, ending in review minutes (Berita Acara, BA) SOURCES Survey shapefile (SHP) channel alignments structure points measured lengths, counts DED drawings (DWG / PDF) layout, long and cross sections, structure details dimensions per channel RAB workbook bill of quantities per channel and structure AHSP analysis and basic prices, budget ceiling REVIEW 1 Normalise channel names and codes units and spelling one key per channel 2 Extract per channel length from SHP section, structures from DWG volume and cost from RAB 3 Match join the three sources per channel and structure flag items missing in any one of them 4 Checks length and section differences structure counts value vs budget ceiling unit-price chain (AHSP) 5 Findings each with source sheet / cell severity: high, medium, low planner confirmation points 6 Review minutes (BA) RAB items · channels · structures · confirmations conclusion: conforms or needs revision Principles Numbers are re-read from the original files before a finding is called severe; the review states differences and asks the planner to confirm, it does not redesign.
Swipe sideways to see the whole diagram. Review flow: shapefile, drawings and estimate are normalised, extracted per canal, matched and checked; findings end in review minutes. View full size

01Problem

Before construction, the detailed designs (survey shapefiles, CAD drawings) and the cost estimates for 28 locations in Tulang Bawang and Mesuji, Lampung had to be checked against each other. Is every priced canal and structure actually in the design? Is every unit price built on the right analysis? Doing that by eye, 28 times, over estimates of about 40 sheets each, is where mistakes hide.

02What I built

A repeatable review pipeline instead of 28 manual checks. Every estimate line is extracted per location; canals and structures are matched between shapefile, drawings and estimate; each location gets review minutes that list what matches, what does not, and the questions the designers must answer. A separate trace follows the unit-price chain: estimate → price-analysis summary → unit-price analysis → base prices.

03How it works

  1. Extract once. Workbooks are opened read-only and extracted once, so parallel checks never compete for heavy files.
  2. One correction file. Manual corrections to canal matching live in a single file, so a rebuild can never silently change a match.
  3. Doubt is written down. Anything uncertain is not decided quietly: it goes to a “needs designer confirmation” section.
  4. Judgement stays human. Pricing findings go into a review workbook with status and comment columns, because pricing judgements stay with the reviewer.

04Results and scale

  • Review minutes for all 28 locations, with 121 items for the designers to confirm.
  • 172 unit-price findings ranked high / medium / low for manual review.
  • The four most serious findings were re-verified against the original source files; the minutes are awaiting final sign-off.

05Try it

The review reads estimates like this one — groups, items, quantities, unit prices, weights. The recap below is fictitious; change an earthwork quantity to see how one line moves every total and weight.

Quantities → bill of quantities

A fictitious 1.2 km canal package. Earthwork quantities come from the cross-sections by average end area × length; edit them to see amounts, subtotals, weights and the total follow.

Illustrative data · fictitious prices (IDR)
Share of subtotal by group

Swipe sideways to see every column.

Illustrative bill of quantities
CodeItemUnitQuantityUnit priceAmountWeight

Weights are what the S-curve uses. VAT shown at 11% for illustration. Nothing here comes from a real project.

All interactive demos

06Stack

  • Python
  • openpyxl
  • python-docx
  • PDF rendering
  • Excel review workbooks
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