Primary Sources are often collected and published as a book(collection of letters for example). A book can also include primary sources in appendices. To locate primary sources on your topic, an easy way is to search OSCAR, the library catalog and to add to your search some keywords describing primary sources such as : letters or diairies, or documents, or sources. For example a search on Theodore Roosevelt and Letters would retrieve the following book: "Theodore Roosevelt and his Times Shown in his Own Letters."
The Environmental Debate: A Documentary History (e-book)
Environmental Issues: Essential Primary Sources (e-book)
Water Rights and the Environment in the United States: a Documentary and Reference Guide (e-book)