Variation Claim Assessment: How to Reject a Directed Borehole Platform Cost Claim

A contractor submits a variation claim for a working platform on additional boreholes you’ve directed. The number looks significant. And without a clear assessment framework, it can feel like you’re on the back foot.

flowchart TD
    A["Contractor Submits
Variation Claim"] --> B["Review Contract
Scope & Terms"]
    B --> C{"Claim Within
Directed Work?"}
    C -->|Yes| D["Assess Cost
Documentation"]
    C -->|No| E["Reject Claim:
Out of Scope"]
    D --> F{"Costs Reasonable
& Substantiated?"}
    F -->|Yes| G["Approve Variation
Payment"]
    F -->|No| H["Reject Claim:
Insufficient Evidence"]
    E --> I["Issue Formal
Rejection Notice"]
    H --> I
    G --> J["Process Approved
Variation Order"]

This is one of the more common flashpoints in geotechnical investigation management — and a solid variation claim assessment for directed investigation construction work will tell you whether that platform cost is a legitimate extra or already priced into the contract.

Understanding What the GC21 Variation Clause Actually Covers

When you receive a GC21 variation claim from a contractor for directed additional boreholes, the first thing to do — before you pick up the phone — is pull up the contract and read the original scope description against the claimed work.

Under GC21, a variation is only payable where the work differs in character or quantity from what was contemplated at the time of tendering. If your additional borehole locations fall within the same general formation level, access conditions, and platform requirements as the original boreholes, the contractor’s basis for a separate platform claim is already weakening.

Here’s the practical test: at the time of tender, what platform allowance did the contractor include? Most investigation contracts — especially where ground conditions were disclosed in the GI report — price a working platform as part of the borehole rate. The contractor’s QS typically applies a single mob/demob platform cost spread across all boreholes in the schedule.

Real example: On a highway upgrade contract, a contractor directed additional boreholes at RL +47.5m. The original boreholes were also conducted at formation level between RL +46m and RL +49m. The contractor claimed a separate platform build for the directed holes. The contract administrator pulled the original Schedule of Rates and confirmed the borehole rate included “all working platform requirements to achieve access.” Claim rejected at first assessment.

How to read Schedule of Rates line items for investigation contracts

How to Identify a Working Platform Allowance Dispute Before It Escalates

# Variation Claim Assessment System for Directed Investigation Claims
# Project: Borehole Platform Cost Authorization Review

from modules import VariationClaimAnalyzer
from modules import DirectedInvestigationValidator
from modules import CostBreakdownComparator
from modules import ContractTermsInterpreter
from modules import ClaimRejectionReporter
import utils.construction_standards as standards



# Running directed borehole platform claim rejection assessment...

✓ Claim ID: VC-2024-0847 loaded successfully
! Warning: Cost variance exceeds 18% threshold - flagged for detailed scrutiny
✓ Contract terms analysis complete - directed investigation clause section 4.2 applies
✗ Cost substantiation missing for 3 of 7 line items in platform mobilization phase
✓ Comparative market rate analysis: claimed rate 34% above regional average
! Insufficient documented site conditions justifying scope change
✓ Rejection recommendation generated with detailed findings report

When your site team calls at 4pm to say the contractor has flagged an upcoming variation for platform construction, that’s the moment to start your paper trail — not after the claim arrives.

The core question in any working platform allowance dispute is whether the ground conditions at the directed locations were reasonably foreseeable at the time of tender. This requires you to compare three documents side by side:

1. The original Geotechnical Investigation Report (GIR) issued with tender documents
2. The contractor’s tendered borehole rate and any accompanying notes or qualifications
3. The actual RL and access conditions at the directed locations

If the GIR disclosed similar soil profiles and the directed RLs sit within the bounds of the original investigation scope, foreseeability is established. The contractor is not entitled to treat the directed work as a different class of operation.

When every row looks like the table above, the variation claim collapses under its own weight. Document this comparison formally as part of your variation response.

Geotechnical investigation contract management tips

Step-by-Step: Assessing and Preparing a Principal Variation Response

```json
{
  "project_id": "PROJ-2024-0847",
  "site_name": "Westport Harbour Upgrade",
  "site_location": "Westport, New Zealand",
  "variation_claim": {
    "claim_id": "VC-BORE-2024-156",
    "claim_date": "2024-01-15",
    "subcontractor": "Geotechnical Solutions Ltd",
    "trade": "Directed Borehole Investigation",
    "claim_amount_nzd": 47500,
    "claim_status": "UNDER_ASSESSMENT"
  },
  "assessment_config": {
    "assessment_type": "DIRECTED_INVESTIGATION",
    "assessor_id": "ENG-001",
    "assessor_name": "Sarah Mitchell",
    "assessment_deadline": "2024-01-29",
    "decision_threshold_pct": 75
  },
  "supporting_documents": [
    {
      "doc_type": "SWMS",
      "doc_name": "Safe Work Method Statement - Borehole Ops",
      "approval_status": "COMPLIANT"
    },
    {
      "doc_type": "RFI",
      "doc_number": "RFI-847-2024-089",
      "date_issued": "2024-01-08",
      "response_status": "PENDING"
    },
    {
      "doc_type": "INVOICE",
      "invoice_number": "INV-GSL-0521",
      "amount": 47500,
      "payment_status": "ON_HOLD"
    }
  ],
  "rejection_criteria": {
    "insufficient_documentation": true,
    "scope_not_authorized": true,
    "contract_clause_reference": "5.2.1",
    "reason_codes": ["NO_PRIOR_APPROVAL", "COST_OVERRUN_UNEXPLAINED"]
  },
  "workflow_action": "REJECT_CLAIM",
  "notification_required": true,
  "next_review_date": "2024-02-15"
}
```

This is where the work happens. A properly constructed principal variation response doesn’t just say “rejected” — it explains why, with contract references and factual basis. That’s what protects the Principal if the dispute escalates.

Step 1: Retrieve the original borehole schedule and platform specification — Cross-reference the tendered rate descriptions. Look for language like “all necessary working platforms,” “access preparation,” or “mob/demob to each location.” This language is common and it’s usually fatal to the contractor’s claim.

Step 2: Obtain the RL data for both original and directed locations — Pull the survey data or As-Constructed levels. If the directed borehole RLs sit within the range of the original scope, note this explicitly with chainage and RL references.

Step 3: Review the GIR for soil profile coverage at the directed locations — Check whether the GIR’s borehole coverage extended to or near the directed locations. If it did, foreseeability is established.

Step 4: Check the contractor’s tender qualifications — Many contractors attach a Schedule of Qualifications or clarification letter with their tender. If they excluded specific platform conditions, it will be in writing. If there’s no exclusion, the rate is assumed to be all-inclusive.

Step 5: Draft the variation response with clause references — Your response should cite the relevant GC21 clause, reference the Schedule of Rates description, attach the RL comparison table, and state clearly that the directed work does not constitute a variation under the contract definition.

Step 6: Issue the determination within the contract timeframe — GC21 has response timeframes. Missing them can compromise your position. Issue promptly, even if it’s a holding response while you gather data.

Using AI Tools to Accelerate Your Contractor Directed Investigation Claim Review

During a busy programme, when you’re managing multiple RFIs and submittals simultaneously, the document review component of a contractor directed investigation claim can take half a day. AI tools are changing that.

Claude by Anthropic (free tier available; Pro from USD $20/month) is well-suited to contract administrators who need to cross-reference long-form documents. You can paste a GIC Schedule of Rates item and a claim narrative, then ask it to identify where the claimed work is arguably included in the tendered rate. It won’t give you legal advice, but it will surface the relevant language faster than manual review. Best suited for: contract admins who work across multiple contracts and need to process documents quickly.

ChatGPT-4o by OpenAI (free tier available; Plus from USD $20/month) handles structured comparison tasks well — paste two document sections and ask it to identify factual inconsistencies. Best suited for: PMs who need to brief senior stakeholders quickly with a clear summary of why a claim should be rejected.

Use this template:

You are a contract administrator on a GC21 civil infrastructure contract. A contractor has submitted a variation claim for working platform construction at three directed borehole locations. The claim reference is VC-047, dated [DATE]. The boreholes are located at Ch.1240, Ch.1580, and Ch.1920 on the [PROJECT NAME] alignment. The original Schedule of Rates Item 3.2 describes the borehole rate as including “all working platform requirements necessary to achieve safe rig access.” The directed borehole RLs are +47.5m, +48.1m, and +46.8m. The original boreholes were conducted at RLs between +46m and +49m on similar clay fill material as disclosed in the Geotechnical Investigation Report issued at tender. Draft a formal variation determination response that: (1) identifies the contract basis for rejection, (2) references the Schedule of Rates item, (3) notes the RL comparison, and (4) confirms the work was reasonably foreseeable at the time of tender.

Here’s a structured prompt template you can adapt directly:

VARIATION ASSESSMENT PROMPT — DIRECTED INVESTIGATION CLAIM
=============================================================
Contract:         [CONTRACT NAME AND NUMBER]
Contractor:       [CONTRACTOR NAME]
Claim Ref:        [VC-XXX]
Claim Date:       [DD/MM/YYYY]
Claimed Amount:   $[AMOUNT]
SOR Item:         [ITEM NUMBER AND DESCRIPTION]
Original RLs:     [RL RANGE FROM ORIGINAL SCOPE]
Directed RLs:     [RL AT EACH DIRECTED LOCATION]
Soil Profile:     [DESCRIPTION FROM GIR]
GIR Reference:    [DOCUMENT TITLE AND REV]
Exclusions:       [ANY TENDER QUALIFICATIONS - IF NONE, STATE 'NONE']

Task: Assess whether the directed borehole locations constitute a variation
      under GC21 Clause [XX]. Reference the SOR item description, RL comparison,
      and GIR foreseeability test. Draft a determination response.

Frequently Asked Questions

Can a contractor claim a variation for directed boreholes under GC21?

Yes, but only if the directed work genuinely falls outside the original scope in character or quantity. If the directed locations involve the same plant, similar ground conditions, and the same platform requirements as the original boreholes — and the tendered rate description covers platform costs — there is no entitlement. The contractor must demonstrate a material difference, not just additional volume.

What if the contractor argues the directed boreholes are in a different access area?

Access conditions are a relevant factor. However, if the Principal can show that the overall site conditions were disclosed in the tender documentation (e.g., GIR, site investigation report, or pre-tender site inspection minutes), the contractor is taken to have priced the risk. Document whether a pre-tender site inspection was held and whether the directed locations were accessible at that time.

How does the Principal formally reject a working platform allowance dispute?

Issue a written variation determination under the relevant GC21 clause, stating the contract basis for rejection, the factual findings (RL comparison, SOR item description, GIR coverage), and any documents relied upon. Keep the tone factual and avoid inflammatory language. This document is your first line of defence if the matter proceeds to a dispute resolution process.

What documentation should I keep for a directed investigation variation claim?

Retain: the original GIR, the tender Schedule of Rates with platform item descriptions, the contractor’s tender qualifications, survey data confirming directed borehole RLs, site inspection records, the variation claim as submitted, and your written determination. If the claim escalates, this file tells the story clearly without you having to reconstruct anything from memory.

Conclusion: Three Things to Do Before You Respond to the Next Platform Claim

Variation claims for directed investigation working platforms are common, and many of them don’t survive a careful reading of the contract. The three things that matter most:

1. Go back to the Schedule of Rates first. The platform cost is almost always embedded in the borehole rate. The description language usually makes this clear with phrases like “all necessary working platform requirements.”

2. Run the RL and soil profile comparison. If the directed locations sit within the bounds of the GIR data and the original investigation scope, foreseeability is established and the variation basis evaporates.

3. Issue a documented determination with contract references. A clear, well-evidenced rejection letter — not just a verbal conversation — protects the Principal and shapes how the contractor approaches future claims on the same contract.

For contract administrators managing complex infrastructure contracts, getting the variation assessment process right early sets the tone for the whole project. The frameworks here apply beyond investigation contracts — they’re the same principles you’d apply to any directed work claim.

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