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The Effects of Road Transport on Freshwater and Marine Ecosystems

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Criteria are values that are used to derive guidelines or st<strong>and</strong>ards for water uses. Numerical<br />

toxicity criteria are the results <str<strong>on</strong>g>of</str<strong>on</strong>g> toxicity tests.<br />

Guidelines are numerical or narrative statements which when applied should protect the particular<br />

water use that they were developed for. Numerical guidelines should be based up<strong>on</strong> criteria.<br />

St<strong>and</strong>ards are guidelines that have been translated into statutory form.<br />

<str<strong>on</strong>g>The</str<strong>on</strong>g> ANZECC water quality guidelines (ANZECC 2000) are the most comm<strong>on</strong>ly used water quality<br />

guidance values in Australasia. <str<strong>on</strong>g>The</str<strong>on</strong>g> guidelines are based up<strong>on</strong> those <str<strong>on</strong>g>of</str<strong>on</strong>g> CCME (1999).<br />

6.3.2 General Water Quality<br />

Nutrients<br />

As noted above MfE (1992, 1994) has provided guidance in relati<strong>on</strong> to what are c<strong>on</strong>sidered to be<br />

acceptable changes in receiving water quality in relati<strong>on</strong> to nutrients. No specific water quality<br />

guidelines were provided by MfE (1992) <strong>and</strong> subsequent to the release <str<strong>on</strong>g>of</str<strong>on</strong>g> that document, regi<strong>on</strong>al<br />

plans have c<strong>on</strong>tinued the use <str<strong>on</strong>g>of</str<strong>on</strong>g> narrative statements rather than identifying particular guidelines for<br />

dissolved inorganic nitrogen <strong>and</strong> phosphorus. Specific guidelines were not identified as adverse<br />

nutrient related effects are site specific.<br />

Based up<strong>on</strong> the available data for New Zeal<strong>and</strong> <strong>and</strong> overseas urban <strong>and</strong> road stormwater, provides<br />

both nitrogen <strong>and</strong> phosphorus for plant growth at c<strong>on</strong>centrati<strong>on</strong>s well above those limiting for plant<br />

growth. During the plant growth seas<strong>on</strong>, nutrients may become limiting in waterways as a result <str<strong>on</strong>g>of</str<strong>on</strong>g><br />

uptake by algae <strong>and</strong> macrophytes. Stormwater from roads provides a source <str<strong>on</strong>g>of</str<strong>on</strong>g> both nitrogen <strong>and</strong><br />

phosphorus during storm events. <str<strong>on</strong>g>The</str<strong>on</strong>g> importance <str<strong>on</strong>g>of</str<strong>on</strong>g> stormwater as a source <str<strong>on</strong>g>of</str<strong>on</strong>g> nutrients to freshwater<br />

ecosystems is dependent up<strong>on</strong> the relative c<strong>on</strong>tributi<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> various l<strong>and</strong> uses in the particular<br />

catchment.<br />

Overall, as road transport activities release both nitrogen (e.g., through exhaust emissi<strong>on</strong>s) <strong>and</strong><br />

phosphorus (e.g., through wear <str<strong>on</strong>g>of</str<strong>on</strong>g> asphalt) to the envir<strong>on</strong>ment. Stormwater from road run<str<strong>on</strong>g>of</str<strong>on</strong>g>f will<br />

c<strong>on</strong>tribute to plant growth in freshwater ecosystems. <str<strong>on</strong>g>The</str<strong>on</strong>g> net c<strong>on</strong>tributi<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> vehicles to nutrient<br />

loadings in freshwater systems is not known but will be catchment specific (relative to the proporti<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g><br />

vehicles <strong>and</strong> road surface area compared to other sources within the catchment).<br />

Clarity<br />

MfE (1994) defined acceptable changes in water clarity in relati<strong>on</strong> to aesthetic properties <str<strong>on</strong>g>of</str<strong>on</strong>g> water <strong>and</strong><br />

effects <strong>on</strong> euphotic depth. <str<strong>on</strong>g>The</str<strong>on</strong>g> guidelines set out in MfE (1994), have been adopted in various<br />

regi<strong>on</strong>al plans around New Zeal<strong>and</strong>. In most cases the guidance in those plans is narrative or a 10%<br />

change in suspended solids, or clarity (defined by black disc) is set as the guideline. <str<strong>on</strong>g>The</str<strong>on</strong>g> guidance<br />

has been developed to assist managers deal with the potent effects arising from the discharge <str<strong>on</strong>g>of</str<strong>on</strong>g><br />

particulate matter to freshwater ecosystem. In Secti<strong>on</strong> 2 <str<strong>on</strong>g>of</str<strong>on</strong>g> this report, informati<strong>on</strong> was presented that<br />

showed that urban stormwater <strong>and</strong> road/motorway run<str<strong>on</strong>g>of</str<strong>on</strong>g>f typically has moderate to high<br />

c<strong>on</strong>centrati<strong>on</strong>s <str<strong>on</strong>g>of</str<strong>on</strong>g> suspended solids. Data for motorways also indicates that average suspended solids<br />

c<strong>on</strong>centrati<strong>on</strong>s are such that they would be capable <str<strong>on</strong>g>of</str<strong>on</strong>g> reducing the clarity <str<strong>on</strong>g>of</str<strong>on</strong>g> receiving waters close to<br />

the point <str<strong>on</strong>g>of</str<strong>on</strong>g> discharge. <str<strong>on</strong>g>The</str<strong>on</strong>g> actual change <strong>and</strong> significance <str<strong>on</strong>g>of</str<strong>on</strong>g> any effect would be dependent up<strong>on</strong>:<br />

1. <str<strong>on</strong>g>The</str<strong>on</strong>g> suspended solids c<strong>on</strong>centrati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> the stormwater.<br />

2. <str<strong>on</strong>g>The</str<strong>on</strong>g> upstream in-water suspended c<strong>on</strong>centrati<strong>on</strong>.<br />

3. <str<strong>on</strong>g>The</str<strong>on</strong>g> mixing <strong>and</strong> diluti<strong>on</strong> that occurred at <strong>and</strong> downstream from the point <str<strong>on</strong>g>of</str<strong>on</strong>g> entry.<br />

In general, effects would tend to be more significant in small urban stream <strong>and</strong> lakes. Although urban<br />

<strong>and</strong> isolated road stormwater c<strong>on</strong>tains particulate matter, the proporti<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> particulate matter sourced<br />

from vehicles <strong>and</strong> road surface wear compared to other n<strong>on</strong>-road sources (e.g., atmospheric<br />

Kingett Mitchell Ltd<br />

Resource & Envir<strong>on</strong>mental C<strong>on</strong>sultants

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