Writing prompt Grade 11 Careers & CTE
Why Marchenford's Coliform Sample Was Rejected
A grade 11 careers explanatory prompt using a sampling manual, a chain of custody form, and a laboratory rejection notice to explain what makes a sample count.
Objectives
- Students will explain the conditions a compliance sample must meet to be accepted by a certified laboratory.
- Students will use three project documents together to explain why one sample was rejected.
- Students will describe what four different water-sector roles do after a sample is rejected.
Vocabulary
Key words: chain of custody, holding time, preservative, certified laboratory, invalidated sample, monitoring violation
Teacher overview
Students write an explanatory piece for a utility's orientation packet that explains why a routine compliance sample was rejected and what each person in the chain does next. The task rests on a distinction that new employees miss regularly. A rejection describes the record rather than the water, because a sample the laboratory cannot defend counts as no sample at all, which is how a utility with safe water ends up with a monitoring violation. Students who miss that distinction tend to write about contamination that never occurred, so the point is worth stating before they read the documents.
Prompt
Background. Marchenford Water is a fictional utility serving a small city. Every month its field sampler collects routine bacteriological samples at fixed sites around the distribution system. The samples go to Strathmoor Analytical, a fictional certified laboratory 40 minutes away.
A sampler hired three weeks ago collected the sample described below. The laboratory rejected it. The water itself was never in question. Read the three documents, then write the explanation.
Source A: excerpt from the fictional Marchenford sampling manual
| Requirement | What the manual says |
|---|---|
| Bottle | Use a laboratory-supplied sterile bottle containing sodium thiosulfate, which neutralizes the chlorine in the sample |
| Site | Collect only at a site listed in the approved sampling plan, and record the site number on the form |
| Field data | Record the chlorine residual and the time of collection at the tap |
| Holding time | The laboratory must begin the analysis within 30 hours of collection |
| Temperature | The cooler must hold the samples at or below 10 degrees Celsius until the laboratory receives them |
| Chain of custody | Every transfer is signed and timed by the person releasing the sample and the person receiving it |
Source B: the fictional chain of custody form, as the sampler filled it in
| Field | What was written |
|---|---|
| Site number | Left blank |
| Collected by | J. Ferris |
| Date and time collected | Tuesday, 9:15 in the morning |
| Chlorine residual at the tap | 0.8 mg/L |
| Bottle type | Sampler's own clean bottle, laboratory bottles not on the truck |
| Relinquished by, date and time | J. Ferris, no time entered |
| Received by, date and time | Strathmoor Analytical, Thursday, 8:40 in the morning |
Source C: the fictional laboratory rejection notice
| Field | What the notice says |
|---|---|
| Sample | Marchenford routine distribution sample, Tuesday collection |
| Result | Not analyzed, sample rejected |
| Reasons cited | Bottle not laboratory-supplied and not verified sterile; no dechlorination agent; holding time exceeded at receipt; site number missing; custody transfer time not recorded |
| Action required | Recollect at an approved site and deliver within the holding time |
Your task. Write an explanatory piece of four to six paragraphs for the Marchenford orientation packet. Explain what a compliance sample must satisfy before a laboratory will analyze it. Explain why this particular sample was rejected, citing all three documents. Then explain what each of these four people does after a rejection: the field sampler, the certified laboratory analyst, the laboratory quality assurance officer, and the utility's compliance coordinator. Close by stating why a rejected sample matters even when the water is fine. Write for a reader on their first week, and define any term that reader would not already know.
Planning Organizer
Fill in every row before you draft. Each row becomes at least one sentence in your explanation.
| Part of the explanation | What you will write |
|---|---|
| Purpose and audience: who reads this and what they need from it | |
| Requirement 1 from the manual, and why it exists | |
| Requirement 2 from the manual, and why it exists | |
| Requirement 3 from the manual, and why it exists | |
| What the chain of custody form shows, quoting one field | |
| What the rejection notice says, and which manual requirement each reason matches | |
| What the field sampler does next | |
| What the certified laboratory analyst and the quality assurance officer each do | |
| What the compliance coordinator does, including what is reported to the state | |
| Closing: why a rejected sample matters even when the water is fine |
From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.
Exemplar & Rubric
Exemplar response
A compliance sample has to work as a legal record as well as a measurement. The laboratory will only analyze a sample it can defend later, which means it has to know what the sample was collected in, where it came from, when it was collected, and who held it at every step. The Marchenford manual sets those conditions, and Strathmoor Analytical applies them the moment a cooler comes through the door. A sample that fails any one of them is rejected without being tested, and nothing about the water enters into that decision.
Three of the manual's requirements did most of the work in this case. The bottle must come from the laboratory and must contain sodium thiosulfate, because chlorine keeps acting on bacteria inside the bottle and would keep changing the result after collection. The analysis must begin within 30 hours of collection, because the bacteria in the sample can multiply or die off while the bottle waits. The site number must come from the approved sampling plan, because a result only means something if the utility can say which part of the distribution system it describes.
The chain of custody form shows where this sample went wrong. Under bottle type, the sampler wrote that the laboratory bottles were not on the truck and that a personal clean bottle was used instead. The site number field is blank. The sampler recorded a Tuesday collection at 9:15 in the morning, and Strathmoor recorded receipt on Thursday at 8:40, which is well past 30 hours. The sampler also left the relinquished time empty, so there is no record of when the sample changed hands.
The rejection notice lines up with those entries one for one. It cites a bottle that was neither laboratory-supplied nor verified sterile, no dechlorination agent, a holding time exceeded at receipt, a missing site number, and a custody transfer time that was never recorded. Each of those maps to a line in the manual, which is why the notice reads as a checklist rather than a judgment.
Four people carry this forward. The field sampler recollects at an approved site, this time in a laboratory bottle, and delivers within the holding time with every field on the form completed. The certified analyst logs the rejection, keeps the notice with the sample record, and analyzes the replacement when it arrives in condition. The laboratory's quality assurance officer tracks rejections as a pattern, because several from one utility usually point to training or to supplies rather than to one careless morning. The utility's compliance coordinator decides whether the replacement can still be collected inside the monitoring period, notifies the state program if it cannot, and arranges for laboratory bottles to be stocked on every truck.
The reason all of this matters is that a monitoring requirement is met only by a defensible record, and clean water alone does not satisfy it. If the replacement sample does not reach the laboratory inside the monitoring period, Marchenford has failed to monitor, and that becomes a reportable violation even though every tap in the city was safe the whole time. A new sampler should treat the bottle, the site number, and the delivery time as part of the test itself, because a result the laboratory cannot defend does not count for anything.
Rubric
| Criterion | Emerging | Developing | Proficient | Advanced |
|---|---|---|---|---|
| Explanation of requirements | Names no requirement, or restates the manual without explaining it | Names one or two requirements with little explanation | Explains at least three requirements and why each exists | Explains at least three requirements, why each exists, and what would change in the result if it were ignored |
| Use of the three sources | Uses one source, or describes the rejection without evidence | Uses two sources, or quotes without connecting them | Uses all three sources and matches each rejection reason to a manual requirement | Uses all three, matches every reason, and points out an entry on the form that the notice did not need to cite |
| Roles and responsibility | Names fewer than two roles | Names the roles without saying what each does | Describes what all four people do after the rejection | Describes all four accurately and distinguishes the analyst's task from the quality assurance officer's |
| Organization and audience | No visible structure, or written for an expert reader | Structure present but the audience shifts | Four to six ordered paragraphs written plainly for a first-week reader | Ordered paragraphs, plain language, and a closing that gives the new sampler something usable |
| Precision and conventions | Confuses a rejected sample with a failed result | Precision slips in places, and errors distract | Keeps the record and the water distinct, with few errors | Keeps them distinct throughout, uses terms exactly, and is clean in conventions |
Differentiation
Support
Give students the rejection notice and the manual side by side on one page, with the five reasons already numbered, so the matching step is visual rather than remembered. Provide a paragraph outline naming what belongs in each of four paragraphs. Allow the roles section to be written as a labeled list rather than prose.
Extension
Ask students to write the two-sentence correction the compliance coordinator would add to the utility's procedure so this does not recur, then decide whether the fix belongs in training, in supplies, or in the form itself. Students who want a harder version can redesign the chain of custody form so that the missing fields cannot be left blank.
ELL supports
Pre-teach "chain of custody," "holding time," "preservative," "rejected," and "violation" with short definitions and a picture sequence showing a bottle moving from tap to cooler to laboratory, with a signature at each handoff. Provide sentence frames such as "The manual requires ___ because ___," and allow the closing paragraph to be two sentences.
Extensions
Have students find their own state's list of certified drinking water laboratories, which every state publishes, and identify which laboratory would receive samples from their community. Students can also request a blank chain of custody form from a local utility or laboratory and compare its fields with the fictional one in this prompt, then write two sentences on what the real form asks for that this one does not.