How to compare borehole drilling quotes

The most useful comparison is the cost of meeting the same agreed brief, with the same testing, handover and risk allocation. A low drilling rate can be part of a good proposal, but it is not the price of a complete water supply.

This guide focuses on water boreholes. For heating or ground investigation, use the same comparison method with the relevant designer's specification. The checklists below are questions for a quotation exercise, not specifications that every borehole must share.

Give every contractor the same starting information

Prepare one brief covering the site, purpose, demand, access, available ground information, known constraints and required completion date. Send later clarifications to every bidder. Otherwise, one company may price a complete installation while another prices only exploratory drilling.

Ask each contractor to identify the assumptions behind its proposal. These might concern drilling depth, formation, borehole diameter, site access, power supply, water disposal and the extent of the trenching. Keep assumptions beside the quoted price rather than buried in separate emails.

For an early feasibility enquiry, a budget range can be appropriate. Label it as such in your comparison. Do not compare a preliminary allowance with a detailed proposal as though both provide the same level of price certainty.

Identify how the price is calculated

Ask whether the proposal is a fixed price for a defined scope, an estimate, a measured rate, a day rate or a combination. The document's heading is not enough: read the exclusions, quantities and variation clauses.

• Fixed-scope price: what exact outcome and work does the price cover, and which events allow a change?
• Price per metre: which diameter and drilling method does it cover, which materials are additional, and is there a minimum charge?
• Day rate: what counts as a working or chargeable day, and how are downtime, travel and standby treated?
• Allowances: which sums are provisional, what quantity do they assume, and how will the actual charge be established?
• Combined proposal: which elements are fixed and which are remeasured after the work?

Ask whether VAT is included where applicable, how long the offer remains valid and whether mobilisation or return visits are additional. Request clarification in writing before accepting. General nidirect advice on repairs and maintenance also recommends a written scope and a breakdown of costs.

Compare the work package by package

Make a comparison sheet with one row per item and one column per bidder. Use “included”, “excluded”, “allowance” or “not stated”, with a note of any quantity or price. A blank cell should become a question, not an assumed inclusion.

Assessment and permissions

Check desktop work, a site visit, hydrogeological advice, application preparation, fees and any monitoring or reporting. Establish who is responsible for confirming permissions and whether waiting time affects the programme. Investigation consent, abstraction authorisation and disposal of test water are separate matters to clarify with the relevant authority.

Mobilisation and site preparation

Compare transport, access works, working platforms where required, ground protection, welfare arrangements and setup. Ask who supplies power or working water, who checks services and who pays if the rig cannot reach the agreed location. Confirm the access information on which the price depends.

Drilling and completion

Record the priced depth or depth range, finished diameter, proposed construction, casing and sealing allowances. Ask which changes trigger additional rates. A proposal with a lower drilling rate may exclude materials or completion work included by another bidder. Ask the designer to explain differences in construction instead of treating diameters and casing as interchangeable items.

Development and testing

Check whether the price includes preparing the borehole for service, a defined pumping test, measurement and reporting, sampling and laboratory analysis. Ask who interprets the results against your required demand. “Tested” should have a defined meaning, deliverable and acceptance process.

Pump, controls and connection

Check the permanent pump and its design duty, electrical work, controls, alarms if specified, pipework, trenching, pressure equipment, storage and connection to the point of use. Ask whether the pump is provisional pending the test results. A pump supplied at the wrong duty is not equivalent to a system designed around the tested source and your demand.

Treatment and commissioning

Identify whether treatment is excluded, provisionally priced or designed after analysis. Confirm who is responsible for that design, installation, commissioning and operating instructions. BGS recommends appropriate water analysis; the type and extent should be agreed for the intended use. Do not compare a treated supply with an untreated borehole as if they were the same deliverable.

Waste, discharge and reinstatement

Check drilling arisings, water management, removal or disposal, temporary works, final borehole protection and surface reinstatement. Ask exactly what “make good” covers. A quotation might include filling a trench but exclude replacement paving, planting or topsoil.

Handover and aftercare

Compare logs, construction records, test reports, equipment details, operating instructions, warranties and the first service if offered. Establish whether later sampling, servicing, call-outs and consumables are included. Ask who will support the installation if the drilling and pump work are subcontracted to different businesses.

Test the uncertainty before choosing a price

Ask each bidder to explain the consequences of the same scenarios:

1. The target formation is deeper than expected.
2. Extra casing or a different drilling approach is proposed.
3. The source does not meet the required yield.
4. Analysis identifies a need for treatment outside the allowance.
5. Access, weather or an unexpected obstruction delays the work.
6. The borehole is stopped or abandoned.

For each, ask what work would be proposed, what would be payable, who can authorise it and when you would be asked to decide. Include safe completion or decommissioning responsibilities if the investigation is unsuccessful. An unanswered question here can matter more than a small difference in the opening price.

You can compare cost sensitivity without pretending to predict the ground. For an additional-depth scenario, ask for a calculation showing extra metres multiplied by the applicable drilling rate, plus any extra casing, materials, test time and other charges. Request the contractor's calculation and its assumptions. Do not apply a per-metre rate beyond the conditions it was quoted for.

Set a written expenditure limit or decision point appropriate to the contract. Agree who is authorised to approve changes and require an updated cost and scope before extra work proceeds, except for any clearly defined urgent safety provisions.

Compare the programme and payment terms

Record the proposed start window, dependencies, working duration and stages through testing and commissioning. A drilling slot alone is not a completion date for a usable supply. Ask about subcontractor availability, application dependencies, laboratory turnaround and later equipment installation.

Match proposed payment stages to identifiable work or deliverables. Understand the reason for a deposit, the conditions attached to it and what happens if work is delayed or cancelled. Avoid agreeing to pay the whole project cost before the promised work has been completed. Verify any changed payment instructions through a trusted contact channel before transferring funds.

For a domestic contract, ask the contractor to provide the applicable consumer information and cancellation terms. Rights depend on the circumstances of the agreement; seek current consumer advice if anything is unclear. Do not assume a quotation comparison replaces checking the contract.

Choose on the clarified total and the quality of the proposal

Keep three separate figures: the price of clearly included work, stated provisional sums and known exclusions still needing a price. Do not create a single reassuring total by treating unpriced essentials as zero.

Compare the evidence behind the proposal as well as the sums. Can the contractor explain the design, identify the important uncertainties, provide relevant references and describe how testing will support the final installation? A more expensive proposal may include useful work, or it may simply cost more. The comparison sheet should make the reason visible.

A clarification message you can reuse

“Please confirm your price against the attached brief. Identify the included depth, construction, testing, equipment, connection, reinstatement and handover documents. List exclusions and provisional sums, including VAT treatment where applicable. Explain the rates and approval process for extra depth, additional materials, low yield, treatment changes and an unsuccessful borehole. Please also confirm the programme, payment stages, warranty scope and the business responsible for the complete installation.”

Save the final clarifications with the accepted proposal. Make sure they are reflected in the written agreement, rather than relying on a conversation that neither party can later reconstruct.