My comments are general, not sited to your specific conditions or circumstances.  Many zoos have some types of rail transport for visitors and therefore the impacts are often considered reasonable for slow transport and user sight seeing.   

Railways may have some effects to noise and air pollution, habitat change due to fragmentation from crossing habitats, wetlands and streams.  Construction activities in filling or reshaping lands for support of tracks, and proper bridges or culverts for water to flow naturally under tracks without excessive flooding.  The wooden railroad ties may have creosote or other preservative chemicals that might be a concern for some species.  Accidents may occur, so If the railroad is allowed to carry hazardous materials, spills might be possible and spill response and management plans important.  Fires may be caused by friction sparks from heavy loads in rail traffic.  Technology exists for installation of speed controls if that becomes a concern.  

The railway will definitely pose a challenge to Kenyans. Firstly, it is a wrong idea to allow a rail station to pass through the park. In a park like this, children are the most vulnerable followed by the women. The aerosols produced by the fume released by train poses health challenges to the people in the parks. Inhaling such aerosols can increase the potential of asthma.

When these aerosols settle to the ground, the soils and plants in the park will be contaminated. As we know, there is little we can do to stop children from playing with sand in such an environment. When these contaminated soils are picked up and ingested by these kids, it may cause gastro-intestinal problem. Kenya should be prepared to face this challenge. Animals especially birds that have their natural abode within these vegetations may also be affected by these aerosols and a possibility of a decrease in their population is envisaged.

Rivers and streams close to the source of these aerosols are in the danger of been contaminated with heavy metals especially Pb. When the river system is affected, there is a high possibility that the groundwater will also be affected. This singular effect may travel a long distance to contaminate aquifers in the area.

It is advisable that the park is relocated to another favorable condition.