How to pass parent view data when using partial view

I have a dropdownlist in my parent view and when I select a value I want to save that value and use it when I click a button in my partial view. Currently if I click a button in the partial view it will not have the value of the parent view. However, if I move the dropdownlist to the partial view everything works fine, but I would like to keep it in my parent view.

Parent View (This is where the dropdownlist is)

<div class="btn-toolbar">
    <div class="btn-group">
        <button type="button" class="btn btn-primary" id="FetchProcessId">Fetch Process Id</button>
    </div>
</div>

<div class="col-md-3" style="@displayAdminLead">
    <div class="dropdown div-inline">
        @{
            var envlist = new List<SelectListItem>()
            {
                new SelectListItem() {Value = "OAK", Text = "OAK"},
                new SelectListItem() {Value = "QA", Text = "QA"},
                new SelectListItem() {Value = "PROD", Text = "PROD"}


            };
        }
        @Html.DropDownListFor(m => m.EnvironmentName, envlist, "Environment", new {@class = "form-control"})
    </div>
</div>


<div style="overflow: auto">
        @using (Html.BeginForm())
        {
            <div id="FetchProcessIdDiv" style="">
                @Html.Action("FetchProcessId", Model)
            </div>
        }
</div>

Partial View

<table class="table table-hover">
    <tbody>
        <tr>
            <td>System Name:</td>
            <td>
                @Html.DropDownListFor(m => m.FetchProcessIdModel.SystemName, new SelectList(Model.FetchProcessIdModel.DropDownOptions, "valueId", "value"))
            </td>
            <td rowspan="2">@Html.TextAreaFor(m => m.FetchProcessIdModel.Message, 12, 50, null)</td>
        </tr>
        <tr>
            <td>Deliverable Id:</td>
            <td>@Html.TextBoxFor(m => m.FetchProcessIdModel.DeliverableId)</td>
        </tr>
    </tbody>
</table>

<input type="submit" name="submit" class="btn btn-default" value="Fetch Process Id" />

Parent Model

public class ParentModel
{
    public string EnvironmentName { get; set; }
}

Controller

[HttpPost]
    public ActionResult ParentClass(string submit, ParentModel model)
    {
        //omit
        var envName = model.EnvironmentName;
        //I am not seeing a value for model.EnvironmentName at this point
    }